IL314406A

IL314406A - Method and system for detecting intra-body location based on flow

Info

Publication number: IL314406A
Application number: IL314406A
Authority: IL
Inventors: ZELLNER Ido; Pomerantz Itzhak; Milad Hamisa
Original assignee: Afeka Yissumim Ltd; Mor Research Applic Ltd; ZELLNER Ido; Pomerantz Itzhak; Milad Hamisa
Priority date: 2024-01-15
Filing date: 2024-07-18
Publication date: 2025-08-01

Description

METHOD AND SYSTEM FOR IDENTIFYING AN INTRABODY LOCATION BASED ON FLOW FIELD AND BACKGROUND OF THE INVENTION The present invention, in some embodiments thereof, relates to a system and a method for navigating in or to a target body cavity and, more particularly, but not exclusively, to a system and a method for navigating in or to a target body cavity, using color Doppler ultrasound. Background art includes scientific publication "Use of colour Doppler and M- mode ultrasonography to confirm the location of an epidural catheter-a retrospective case series." By Hesham Elsharkawy, M. D., et al. disclosing that "Epidural anesthesia and analgesia has a reported failure rate ranging from 13% to 32%. We describe a technique using colour Doppler and M-mode ultrasonography to determine the position of the epidural catheter after placement in adults". (abstract). Background art includes scientific publication "Color flow Doppler in spinal ultrasound: a novel technique for assessment of catheter position in labor epidurals" by van den Bosch, Oscar FC, et al. disclosing that "Color flow Doppler ultrasound is a feasible and fast way to determine flow in the epidural space in the obstetric population. Its potential clinical uses are confirmation of the epidural catheter position after placement, as well as troubleshooting of unsatisfactory epidural analgesia. Interestingly, our results suggest that epidural catheters predominantly remain at the interspace of insertion." (abstract). Background art includes scientific publication "Settings and artefacts relevant for Doppler ultrasound in large vessel vasculitis." By Terslev, L., et al. disclosing that "Ultrasound is used increasingly for diagnosing large vessel vasculitis (LVV). The application of Doppler in LVV is very different from in arthritic conditions. This paper aims to explain the most important Doppler parameters, including spectral Doppler, and how the settings differ from those used in arthritic conditions and provide recommendations for optimal adjustments. This is addressed through relevant Doppler physics, focusing, for example, on the Doppler shift equation and how angle correction ensures correctly displayed blood velocity. Recommendations for optimal settings are given, focusing especially on pulse repetition frequency (PRF), gain and Doppler frequency and how they impact on detection of flow. Doppler artefacts are inherent and may be affected by the adjustment of settings. The most important artefacts to be aware of, and to be able to eliminate or minimize, are random noise and blooming, aliasing and motion artefacts. Random noise and blooming artefacts can be eliminated by lowering the Doppler gain. Aliasing and motion artefacts occur when the PRF is set too low, and correct adjustment of the PRF is crucial. Some artefacts, like mirror and reverberation artefacts, cannot be eliminated and should therefore be recognised when they occur. The commonly encountered artefacts, their importance for image interpretation and how to adjust Doppler setting in order to eliminate or minimize them are explained thoroughly with imaging examples in this review." (abstract). Background art includes scientific publication ""Sonography Doppler Flow Imaging Instrumentation" By Shah, Aalap, and Abid Irshad disclosing that "Doppler ultrasonography is an essential diagnostic tool in diagnosing and managing various disease processes. The use of Doppler ultrasound by healthcare team members has become increasingly common as the technology has improved and become more cost- effective. Additionally, there has also been an increased use of point-of-care ultrasound as a diagnostic modality. All clinicians need to understand the underlying principles, potential pitfalls, and possible advantages of Doppler ultrasound. This activity will highlight the physics, imaging characteristics, clinical utility, and other key factors (e.g., pitfalls, errors, and safety considerations) pertinent for members of the interprofessional team in the care of patients who undergo Doppler ultrasound examination for diagnosis, monitoring, and management of various disease processes." (abstract). SUMMARY OF THE INVENTION Following is a non-exclusive list including some examples of embodiments of the invention. The invention also includes embodiments which include fewer than all the features in an example and embodiments using features from multiple examples, also if not expressly listed below. Example 1. A method for assisting navigation of an injector to or within a target body cavity using a flow sensor, wherein the method comprises: providing a flow sensor for measuring fluid flow at a region of the tip of said injector; injecting a flow through and out of the injector coordinated with said flow sensor; detecting the flow within the body, using the flow sensor; and determining a placement of said injector based on said detected flow. Example 2. The method according to example 1, wherein the method further comprises coordinating between flow properties and settings of the flow velocity. Example 3. The method according to example 2, wherein the flow sensor is a color Doppler ultrasound device, and wherein the coordinating comprises selecting a flow velocity according to a PRF range or a PRF value of the color Doppler ultrasound device. Example 4. The method according to any of examples 1-2, wherein the injecting comprises providing a pulsatile flow coordinated with said flow sensor. Example 5. The method according to any of examples 2-4, wherein the coordinating comprises adjusting a PFR according to the flow velocity. Example 6. The method according to any of examples 2-5, wherein the coordinating comprises adjusting the frame rate of the color Doppler ultrasound device. Example 7. The method according to any of examples 1-6, wherein the providing comprises using a pump for generating the flow. Example 8. The method according to example 7, wherein the using a pump comprising pre-setting the pump to generate a flow velocity according to said coordinating. Example 9. The method according to example 1, wherein the detecting comprises visualizing the fluid expelled from a tip of the injector, around said tip. Example 10. The method according to any of examples 1-9, wherein said determining comprises identifying placement of the injector’s tip within the body by viewing the flow expelled from the tip of the injector, around said tip within a body cavity. . Example 11. The method according to any of examples 1-9, wherein the determining comprises confirming placement in the target body cavity by viewing the flow within the body cavity. Example 12. The method according to examples 10 or 11, wherein the identifying comprises viewing the flow within the target body cavity and does not exceed beyond the target body cavity.

Example 13. The method of example 1-12, comprises visualizing the fluid flow within the body and functionally assessing the flow, wherein visualizing fluid expansion indicates placement within a body cavity. Example 14. The method according to any of examples 1-13, wherein the providing comprises alternating between forward-flowing and back-flowing. Example 15. The method according to any of examples 10-14, wherein the target body cavity is an epidural space and the injector is an introducer needle or a needle for epidural injection, wherein the determining comprises determining placement in the epidural space. Example 16. The method according to example 15, wherein the method comprises inserting an epidural catheter through the introducer needle and identifying epidural placement of the epidural catheter. Example 17. The method of example 16, wherein the identifying epidural placement of the epidural catheter comprises confirming that a tip of the epidural catheter is not within a blood vessel in the epidural space. Example 18. The method according to any of examples 1-17, comprises monitoring the injector placement within the epidural space, wherein the monitoring can be continuous or intermittent. Example 19. A method for inserting an injector into a target body cavity using a flow sensor, wherein the method comprises: advancing the injector toward a target body cavity; injecting a fluid through the injector; confirming a location of an injector’s tip at a location along a path to the target body cavity by viewing the fluid flow through and out of an injector’s tip, using the flow sensor; reaching the target body cavity. Example 20. The method according to claim 19, wherein the injecting comprises injecting a fluid through the injector while the injector is advancing. Example 21. The method according to any of examples 19-20, wherein advancing comprises advancing in steps and wherein the injecting comprises injecting a fluid through the injector between steps while the injector is static.

Example 22. The method according to any of examples example 19-21, wherein the injecting further comprises providing a flow velocity or a flow pattern which can be detected by the flow sensor. Example 23. The method according to any of examples 19-22, wherein the providing comprises providing a flow velocity or flow pattern which can reduce or avoid aliasing. Example 24. The method according to any of examples 19-23, wherein the flow sensor is a color Doppler ultrasound device and wherein the providing comprises coordinating the flow velocity with a PRF or a PRF range of the color Doppler ultrasound device. Example 25. The method according to any of examples 19-24, wherein the coordinating comprises adjusting the PRF of the color Doppler ultrasound device according to a fluid velocity. Example 26. The method according to any of examples 19-25, wherein the coordinating comprises adjusting the frame rate of the color Doppler ultrasound device. Example 27. The method according to any of examples 24-26, wherein the coordinating comprises setting the flow velocity and the PRF so that the flow is localized on the image to within no more than 5 mm. Example 28. The method according to any of examples 24-27, wherein the providing comprises generating a flow velocity or flow pattern according to said coordinating using a pump. Example 29. A system for identifying placement of an injector, within a body cavity comprising: A flow sensor; and A pump, configured to generate a fluid flow through and out of the injector, wherein the fluid flow can be detected by the flow sensor. Example 30. The system according to example 29, wherein the flow sensor is a color Doppler ultrasound device. Example 31. The system according to examples 29 or 30, comprises a controller, wherein the controller is configured to coordinate between a flow velocity and a PFR of the color Doppler and to determine a desired flow velocity and PFR value.

Example 32. The system according to examples 29-31, wherein the controller is configured to determine pump settings according to the desired flow velocity Example 33. The system according to any of examples 29-32, wherein the pump is a reciprocal pump or peristaltic pump. Example 34. The system according to any of examples 29-33, comprises a pressure sensor, configured to adjust settings of the pump to maintain a desired flow velocity. Example 35. The system according to any of examples 29-34, comprises a user interface, configured for inputting patient-specific information. Example 36. The system according to any of examples 29-35, comprises a user interface, configured for inputting equipment-specific information. Example 37. A system for identifying a placement of an injector, within a body cavity comprising: A flow sensor; and A pump, configured to generate a fluid flow through and out of the injector, wherein the flow sensor and the pump are configured to be operated is synchronization, wherein the fluid flow can be detected by the flow sensor. Example 38. The system according to example 37, wherein the flow sensor is a color Doppler ultrasound device. Example 39. The system according to any of examples 37-38, wherein the flow sensor is a color Doppler ultrasound device. Example 40. The system according to any of examples 38-39 , comprising a controller, wherein the controller is configured to coordinate between flow properties and settings of the flow velocity sensor. Example 41. The system according to example 40, , wherein the controller is configured to coordinate between a flow velocity and a PFR or a PFR range of the color Doppler and to determine a desired flow velocity and PFR value. Example 42. The system according to any of examples 40 -41, wherein the controller is configured to adjust the PRF of the color Doppler ultrasound device according to a fluid velocity. Example 43. The system according to any of examples 40-42 , wherein the controller is configured to adjust the frame rate of the color Doppler ultrasound device.

Example 44. The system according to any of examples 40-43 , wherein the controller is configured to determine pump settings according to the desired flow velocity. Example 45. The system according to any of examples 40-44 , wherein the controller is configured to set the flow to alternate between forward-flowing and back- flowing and wherein the pump enables such a flow. Example 46. The system according to any of examples 40-45 , wherein the pump is a reciprocal pump or peristaltic pump. Example 47. The system according to any of examples 40-46 , wherein the pump is configured to generate a pulsatile flow coordinated with said flow sensor. Example 48. The system according to any of examples 40-47 , wherein the controller is configured to set a flow velocity or a flow pattern which can reduce or avoid aliasing. Example 49. The system according to any of examples 40-48 , comprises a pressure sensor, configured to adjust settings of the pump to maintain a desired flow velocity. Example 50. The system according to any of examples 40-49 , comprises a user interface, configured for inputting patient-specific information. Example 51. The system according to any of examples 40-50 , comprises a user interface, configured for inputting equipment-specific information. Example 52. The system according to any of examples 40-51 , comprising a screen for visualizing the fluid expelled from a tip of the injector, around said tip, using said flow sensor. Example 53. The system according to any of examples 40-52 , configured for visualizing the injector upon placement, within the target body cavity. Example 54. The system according to any of examples 40-53 , wherein the controller is configured to set the flow velocity and the PRF so that the flow is localized on an image to within no more than 5 mm. Example 55. The system according to any of examples 40-54 , wherein the controller is configured to coordinate between flow properties and settings of the flow velocity sensor such that the flow can be viewed within the body cavity. Example 56. The system according to any of examples 40-54 , wherein the controller is configured to coordinate between flow properties and settings of the flow velocity sensor such that the flow can be viewed within the target body cavity and does not exceed beyond the target body cavity. Example 57. The system according to any of examples 51-56 , configured for visualizing the injector while advancing toward the body cavity. Example 58. The system according to any of examples 37-57 , configured for monitoring the injector placement within the body cavity, wherein the monitoring can be continuous or intermittent. Example 59. The system according to any of examples 37-58 , wherein the body cavity is an epidural space. Example 60. The system according to any of examples 59, wherein the injector is configured for inserting into the epidural space, and wherein the injector is an introducer needle or a needle for epidural injection. Example 61. A method for detecting an injector to or within a target body cavity using a flow sensor, wherein the method comprises: providing a flow sensor for measuring fluid flow at a region of a tip of said injector; detecting a flow near the tip of the injector within the body, using the flow sensor; providing a system configured for synchronizing the flow with the flow sensor; and determining a placement of said injector based on a detection of the flow within the body cavity, using the flow sensor. Example 62. The method according to example 61, wherein the synchronizing comprises coordinating between flow properties and settings of the flow sensor. Example 63. The method according to example 62, wherein the flow sensor is a color Doppler ultrasound device, and wherein the coordinating comprises selecting a flow velocity according to a PRF range or a PRF value of the color Doppler ultrasound device. Example 64. The method according to any of examples 61-63, wherein the f flow is a pulsatile flow coordinated with said flow sensor. Example 65. The method according to any of examples 63-64 , wherein the coordinating comprises adjusting a PFR of the color Doppler ultrasound device according to the flow velocity.

Example 66. The method according to any of examples 63-64 , wherein the coordinating comprises adjusting the frame rate of the color Doppler ultrasound device. Example 67. The method according to any of examples 62-66 , wherein the providing comprises using a pump for generating the flow. Example 68. The method according to example 67, wherein the using a pump comprising pre-setting the pump to generate a flow velocity according to said coordinating. Example 69. The method according to any of examples 61-68 , wherein the detecting comprises visualizing the fluid expelled from a tip of the injector, around said tip. Example 70. The method according to any of examples 61-69 , wherein said determining comprises identifying placement of the injector’s tip within the body by viewing the flow expelled from the tip of the injector, around said tip within a body cavity. Example 71. The method according to any of examples 61-70 , wherein the determining comprises confirming placement in the target body cavity by viewing the flow within the body cavity. Example 72. The method according to examples 70 or 71 , wherein the identifying comprises viewing the flow within the target body cavity and does not exceed beyond the target body cavity. Example 73. The method according to any of examples 61-72 , comprises visualizing the fluid flow within the body and functionally assessing the flow, wherein visualizing fluid expansion indicates placement within a body cavity. Example 74. The method according to any of examples 61-73 , wherein the providing comprises alternating between forward-flowing and back-flowing. Example 75. The method according to any of examples 70-74 , wherein the target body cavity is an epidural space and the injector is an introducer needle or a needle for epidural injection, wherein the determining comprises determining placement in the epidural space. Example 76. The method according to example 75, wherein the identifying comprises identifying epidural placement of an epidural catheter placed within the introducer needle.

Example 77. The method of example 76, wherein the identifying epidural placement of the epidural catheter comprises confirming that a tip of the epidural catheter is not within a blood vessel in the epidural space. Example 78. The method according example 77, comprises monitoring the injector placement within the epidural space, wherein the monitoring can be continuous or intermittent. Example 79. The method according to any of examples 61-78 , wherein the providing comprises providing a flow velocity or flow pattern which can reduce or avoid aliasing. Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting. As will be appreciated by one skilled in the art, aspects of the present disclosure may be embodied as a system, method, or computer program product. Accordingly, aspects of the present disclosure may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, microcode, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a "circuit," "module" or "system" (e.g., a method may be implemented using "computer circuitry"). Furthermore, some embodiments of the present disclosure may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon. Implementation of the method and/or system of some embodiments of the present disclosure can involve performing and/or completing selected tasks manually, automatically, or a combination thereof. Moreover, according to actual instrumentation and equipment of some embodiments of the method and/or system of the present disclosure, several selected tasks could be implemented by hardware, by software or by firmware and/or by a combination thereof, e.g., using an operating system.

For example, hardware for performing selected tasks according to some embodiments of the present disclosure could be implemented as a chip or a circuit. As software, selected tasks according to some embodiments of the present disclosure could be implemented as a plurality of software instructions being executed by a computer using any suitable operating system. In some embodiments of the present disclosure, one or more tasks performed in method and/or by system are performed by a data processor (also referred to herein as a "digital processor", in reference to data processors which operate using groups of digital bits), such as a computing platform for executing a plurality of instructions. Instruction executing elements of the processor may comprise, for example, one or more microprocessor chips, ASICs, and/or FPGAs. Optionally, the data processor includes a volatile memory for storing instructions and/or data and/or a non-volatile storage, for example, a magnetic hard-disk and/or removable media, for storing instructions and/or data. Optionally, a network connection is provided as well. A display and/or a user input device such as a keyboard or mouse are optionally provided as well. Any of these implementations are referred to herein more generally as instances of computer circuitry. Any combination of one or more computer readable medium(s) may be utilized for some embodiments of the present disclosure. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device. A computer readable storage medium may also contain or store information for use by such a program, for example, data structured in the way it is recorded by the computer readable storage medium so that a computer program can access it as, for example, one or more tables, lists, arrays, data trees, and/or another data structure. Herein a computer readable storage medium which records data in a form retrievable as groups of digital bits is also referred to as a digital memory. It should be understood that a computer readable storage medium, in some embodiments, is optionally also used as a computer writable storage medium, in the case of a computer readable storage medium which is not read-only in nature, and/or in a read-only state. Herein, a data processor is said to be "configured" to perform data processing actions insofar as it is coupled to a computer readable medium to receive instructions and/or data therefrom, process them, and/or store processing results in the same or another computer readable medium. The processing performed (optionally on the data) is specified by the instructions, with the effect that the processor operates according to the instructions. The act of processing may be referred to additionally or alternatively by one or more other terms; for example: comparing, estimating, determining, calculating, identifying, associating, storing, analyzing, selecting, and/or transforming. For example, in some embodiments, a digital processor receives instructions and data from a digital memory, processes the data according to the instructions, and/or stores processing results in the digital memory. In some embodiments, "providing" processing results comprises one or more of transmitting, storing and/or presenting processing results. Presenting optionally comprises showing on a display, indicating by sound, printing on a printout, or otherwise giving results in a form accessible to human sensory capabilities. A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Program code embodied on a computer readable medium and/or data used thereby may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing. Computer program code for carrying out operations for some embodiments of the present disclosure may be written in any combination of one or more programming languages, including an object-oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. Additionally or alternatively, sequences of logical operations (optionally logical operations corresponding to computer instructions) may be embedded in the design of an ASIC and/or in the configuration of an FPGA device. The program code may execute entirely on the user’s computer, partly on the user’s computer (e.g., as a stand-alone software package), partly on the user’s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user’s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). Some embodiments of the present disclosure may be described below with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the present disclosure. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks. The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. Some of the methods described herein are generally designed only for use by a computer; and may not be feasible or practical for performing purely manually, by a human expert. A human expert who wanted to manually perform similar tasks, such inspecting objects, might be expected to use completely different methods, e.g., making use of expert knowledge and/or the pattern recognition capabilities of the human brain, which would be vastly more efficient than manually going through the steps of the methods described herein. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced. In the drawings: FIG. 1A is a simplified block diagram illustration of a system for assisting navigation in or to a target cavity space using a velocity sensor, in accordance with some exemplary embodiments of the invention; FIG. 1B is a a simplified block diagram illustration of a computerized system for assisting navigation in or to a target cavity space using a velocity sensor, in accordance with some exemplary embodiments of the invention; FIGs. 2A-B depict a system for assisting navigation in or to an epidural space using a color Doppler ultrasound, in accordance with some exemplary embodiments of the invention; FIG. 3 is a simplified flowchart of a method for reaching a target body cavity, using a system for assisting navigation in or to a target cavity space using a velocity sensor, in accordance with some exemplary embodiments of the invention; FIG. 4 is a simplified flowchart of a method to assist navigation in or to a target cavity space, using a flow sensor, in accordance with some exemplary embodiments of the invention; FIG. 5A is a graph illustrating a timeline of a procedure for navigating in or to a target body cavity, in accordance with some exemplary embodiments of the invention; FIG. 5B is a graph illustrating an example of coordination between the fluid pattern and the color Doppler ultrasound settings, in accordance with some exemplary embodiments of the invention; FIG. 6A is a schematic side cross-sectional view of an injector placed within the epidural space and, in accordance with some exemplary embodiments of the invention; FIG. 6B is a schematic example of a visualization of an injector placed within the epidural space using a color Doppler ultrasound device, in accordance with some exemplary embodiments of the invention; FIG. 7A is a schematic side cross-sectional view of injectors misplaced out of the epidural space, in accordance with some exemplary embodiments of the invention; FIG. 7B is a schematic example of a visualization of injectors misplaced out of the epidural space using a color Doppler ultrasound device, in accordance with some exemplary embodiments of the invention; FIG. 8 is a schematic curly side cross-sectional view of injectors misplaced out of the epidural space, in accordance with some exemplary embodiments of the invention; FIGs. 9A-B depict a flowchart of a method for navigating in or to an epidural space, using a color Doppler ultrasound device, in accordance with some exemplary embodiments of the invention; FIGs. 10A-B depict a flowchart of a method for reaching the epidural space by detecting a flow thereto, using a color Doppler ultrasound, in accordance with some exemplary embodiments of the invention; FIGs. 11A-B depict a flowchart of a method for navigating in or to a cavity space using backflow, in accordance with some exemplary embodiments of the invention; and FIGs. 12A-B depict an exemplary pump of a system for navigating in or to a target body cavity, in accordance with some exemplary embodiments of the invention. DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION The present invention, in some embodiments thereof, relates to a system and a method for navigating in or to a body cavity and, more particularly, but not exclusively, to a system and a method for navigating in or to a body cavity using flow sensing. An aspect of some embodiments of the invention relates to detecting a flow within a body cavity space, where the flow is provided in a controlled manner, using a pump. In some embodiments, the detection is performed using a flow sensor which is used for detecting the placement of a fluid flowing out of an opening of a medical implement, such as an administration tool (e.g., injector) in the body. The placement of the flow indicates the placement of the administration tool opening, such that a flow located within a target body cavity indicates that the administration tool opening is positioned therewithin. A method of detection in accordance with some embodiments has the potential advantage of simplifying placement identification of an administration tool within a body cavity, which may have a particular use for inexperienced practitioners. The method may have an additional particular use for cases where there is difficulty in reaching a target cavity space and/or difficulty in confirming reaching thereto. In addition, the method potentially reduces and/or prevents misplacement of the administration tool, which might cause adverse side effects and/or endanger the patient. In some embodiments, the method comprises flowing the fluid through and/or out of the administration tool in a manner that allows and/or improves the detection and/or measurements of the fluid motion.

In some embodiments, the method comprises flowing a fluid through the administration tool and out to the body, and detecting the fluid movement (e.g., flow and/or velocity) within the administration tool, at the emergence from the administration tool, and/or out of the administration tool, within the patient’s body. In some embodiments, the method comprises visualizing the motion of tissues and/or cavity walls, for example, visualizing expansion and/or contraction of a cavity space, as a result of a flow thereto. In some embodiments, the method comprises flowing the fluid through and/or out of the administration tool such that the motion thereof (e.g., flow and/or velocity) can be detected by the flow sensor. In some embodiments, the flow sensor is a Doppler ultrasound device, optionally, a color Doppler ultrasound device which can detect flow within the body, and optionally imaging to visualize the flow. In some embodiments, the method comprises coordinating between the flow velocity and the PRR (Pulse repetition rate) or PRF (Pulse repetition frequency) of the Doppler ultrasound device. In some embodiments, the flow velocity is selected according to the PRF and/or PFR range. which defines the maximum measurable velocity (e.g., maximum measurable Doppler shift), having the potential advantage of reducing aliasing. In some embodiments, the coordination between the flow velocity and the PRF potentially reduces spatial smearing such that the dimensions of the visualized flow are smaller than the dimensions of the target cavity space, such that the flow can be detected within the limits of the space, having the potential advantage of reducing false -positive placement. In some embodiments, additionally or alternatively, the PRF can be adjusted according to a selected velocity and/or velocity range. In some embodiments, the method further comprises adjusting the frame rate of the Doppler ultrasound. In some embodiments, the method comprises flowing the fluid through and/or out of the administration tool in a non-uniform, modulated manner. For example, a pulsatile flow. In some embodiments, a pulsatile flow can include negative flow pulses (e.g., backflow pulses) every one or more positive pulses (e.g., forward flow pulses).

For example, generating a negative pulse every few positive pulses, such as a negative pulse every three positive pulses. In some cases, the fluid volume of a negative pulse can be smaller than the volume of a positive pulse. In some embodiments, the alternating negative-positive pulsatile flow allows to control of the overall forward speed of the fluid while reducing the total flow rate and/or overall volume of injected fluid, having the potential advantage of reducing and/or avoiding the risk of over-filling the target cavity space and/or surrounding tissues. In some embodiments, alternating negative-positive pulsatile flow allows alignment of the total flow rate and/or overall volume of injected fluid with the administration requirements of an anesthetic, analgesic, and/or any other medicine such that thereof can be used as the injected fluid used for visualization. This alignment has the potential advantage of reducing and/or avoiding the risk of over-dosing the patient. In some embodiments, the alternating negative-positive pulsatile flow is visualized by alternating two colors and/or change in scales of two colors, having the potential advantage of improving flow visualization in and/or to the target cavity space and/or easing the detection of the flow therewithin. In some embodiments, the backflow can be used to identify placement within a target cavity space by assessing the backflow therefrom. In some embodiments, a resistance to negative flow from the target cavity space differs from a resistance to negative flow from surrounding tissues and/or other cavities. In some embodiments, the amount (e.g., volume) of fluid that can be drawn back from the target cavity space differs from the amount of fluid that can be drawn back from surrounding tissues and/or other cavities. In some embodiments, alternatively or additionally, to pulsatile flow, the flow within the administration tool can be continuous and/or substantially continuous. In some embodiments, a sufficiently low velocity and/or fluid flow together with an administration tool having a wide enough diameter can result in the fluid emerging from the administration tool in drops. Alternatively or additionally, the fluid flow at the emergence of the administration tool can be continuous. In some embodiments, the flow is generated using a pump, which provides a desired flow velocity and/or a desired flow pattern. Using a pump has the potential advantage of improving the control over the flow.

In some embodiments, the operations of the pump and the flow sensor are synchronized in time, having the potential advantage of enabling flow detection and/or improving the measurements of the fluid motion. An aspect of some embodiments of the invention relates to a method for navigating an administration tool toward a body cavity space, under a vision of fluid flowing through and/or out thereof. In some embodiments, the vision is achieved by viewing a flow injected into the space using a flow sensor. This method has the potential advantage of reducing and/or avoiding the risk of reaching other cavities and/or tissues than the target body cavity which might lead to misplacement of the administration tool. In addition, the method has the potential advantage of simplifying medical procedures that require inserting an administration tool into a body cavity, which may have a particular use for inexperienced practitioners. In some embodiments, the flow sensor is a Doppler ultrasound device, optionally a color Doppler ultrasound device. In some embodiments, the flow properties (such as velocity and/or pulse rate) are coordinated with the settings of the color Doppler ultrasound device. This coordination potentially allows detection of the flow within a patient’s body and has the potential advantage of reducing and/or avoiding aliasing and/or imagining artifacts. In some embodiments, the operation of the pump is synchronized in time with the operation of the sensor, optionally, to implement this coordination. In some embodiments, the flow is provided using a pump, which can provide a controlled flow having the desired properties. In some embodiments, the desired flow has a non-uniform pattern which might be challenging to obtain without using a pump. Additionally, using a pump potentially frees a hand of the practitioner from injecting the fluid, such that the practitioner can insert the administration tool using one hand and hold a prob of the Doppler ultrasound, using the other hand. This has the potential advantage of reducing the practitioner’s need for assistance. In some embodiments, the pump can be activated automatically by the system, and/or by the anesthesiologist in a manner that does not require using hands. For example, by voice activation mechanism and/or by a foot pedal positioned the floor. In some embodiments, the flow velocity and/or pulse rate and the pulse repetition frequency (PRF) of the color Doppler ultrasound device are coordinated, potentially allowing to detect the flow through and/or out of the advanced administration tool, and having the potential advantage of improving the detection by reducing aliasing and/or imaging artifacts. Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings and/or the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways. Referring now to the drawings, Figs. 1A showing a simplified block diagram illustration of a system for assisting navigation in or to a target cavity space using a flow sensor, in accordance with some exemplary embodiments of the invention. In some embodiments, system 100 comprises an injector 102 which injects fluid, a flow sensor 104 which can sense, and optionally visualize the injected fluid, and a pump 106 which moves the injected fluid so as to make it visible to flow sensor 104. In some embodiments, the injector 102 is configured to penetrate a patient’s skin and/or be advanced toward the cavity space. In some embodiments, injector 1comprises an inner lumen for introducing a fluid (such as liquid, gas, suspension, and/or mix of any combination thereof) into the patient’s body. In some embodiments, injector 102 comprises and/or is connected to a container with a piston for injecting the fluid into the patient’s body. In some embodiments, flow sensor 104 is configured to detect the flow of the injected fluid. In some embodiments, flow sensor104 comprises an imaging device including a screen for visualizing the flow thereon. In some embodiments, flow sensor 104 is a Doppler ultrasound device. In some embodiments, the Doppler ultrasound device is a color Doppler ultrasound device. In some embodiments, Doppler ultrasound device 104 includes a probe that comprises an ultrasound transducer. In some embodiments, color Doppler ultrasound device 104 is used to view the fluid expelled from injector 102 into the cavity space, optionally the fluid flow within the body cavity. In some embodiments, color Doppler ultrasound device 104 is used to view the path of injector 102 within the body. In some embodiments, the path of injector 102 within the body can be visualized using a non-Doppler mode.

In some embodiments, using a color Doppler ultrasound potentially allows visualization of relatively low velocities. In some embodiments, the color Doppler ultrasound settings are adjusted to visualize relatively low velocities, for example as described in this document. In some embodiments, relatively low velocities of the injected fluid have the potential advantage of reducing the risk of over-filing body tissues and/or cavities, which can lead to distortion of the anatomy. In addition, in some embodiments, the relatively low velocities allow the use of an anesthetic, analgesic, and/or any other medicine as the injected fluid, having the potential advantage of reducing and/or avoiding overdosing the patient. In some embodiments, the frequency range of the ultrasound transducer, which dictates the penetration depth of the ultrasound is selected according to the targeted body cavity. In some embodiments, the ultrasound transducer emits waves with frequencies between 2-14 MHz. For example, for viewing a flow within the epidural space, color Doppler ultrasound 104 comprises a transducer that emits waves with frequencies between 2-5 MHz and/or 5-14 MHz can be used. In some embodiments, color Doppler ultrasound device 104 is a pulsed waved Doppler (PW-Doppler). PW-Doppler, in addition to detecting velocity vector or magnitude of viewed items, such as fluid, allows to optionally calculate the distance of the "reflector" (e.g., fluid flow) within the body and/or to define a specific region of interest (e.g., target body cavity) to be viewed. It is noted that although, in this document, description is generally with referent to color Doppler ultrasound, other Doppler ultrasound modulation techniques can be used, such as Power Doppler, , M-mode ultrasound, Duplex Doppler, Pulse Wave Doppler and/or Continues Wave Doppler. In some embodiments, color Doppler modulation has the potential advantage of having a relatively intuitive visualization and/or user-friendly output. In some embodiments, the fluid is flowed at a velocity that is coordinated with the settings and/or properties of the Doppler ultrasound transducer. This coordination has the potential advantage of improving the detection and/or measurements of the viewed flow. Alternatively or additionally, the settings of the Doppler ultrasound are coordinated with the flow properties (e.g., flow velocity and/or flow pattern).

In some embodiments, the fluid is flowed in a non-uniform, modulated manner. In some embodiments, the flow is pulsatile. It should be noted that Fig, 5B is a idealized representation of a pulsatile flow. In some embodiments, a pulsatile flow can emerge from injector 102 in drops. In some embodiments, the pulsatile flow allows further control of the fluid velocity and/or the amount (e.g., flow rate) of the injected fluid, having the potential advantage of further reducing and/or avoiding over-filing body cavities and/or tissues. In some embodiments, a pulsatile flow, which optionally, emerges from injector 102 in drops, is visualized by color Doppler ultrasound device 104 as flickering, having the potential advantage of improving the visualization and/or easing the detection of the flow emerging from injector 102. In some embodiments, the pulsatile flow defines fluid emergence in drops, from injector 102. In some embodiments, the pulsatile flow enables the integration of backflow pulses in the viewing process, having the potential advantage of improving the visualization of the flow emerging from injector 102, as described later. Additionally, integrating backflow pulses potentially improves the ability to control the overall speed of the fluid expelled from injector 102. In some embodiments, alternatively or additionally to pulsatile flow, the fluid can be flowed continuously. In some embodiments, a continuous flow can emerge from injector 102 in drops, for example, if the fluid velocity and/or fluid flow are low enough, together with a sufficiently wide injector 102. In some embodiments, the fluid flow at the emergence of injector 102 can be continuous. In some embodiments, the continuous flow out of injector 102 allows the fluid to be a medicine that requires continuous administration to the patient. In some embodiments, ultrafast ultrasound can be used to detect a continuous flow. In some embodiments, an ultrasound probe can be fixed and/or attached to a patient having the potential advantage of reducing and/or avoiding the need to hold the probe during the procedure. For example, the probe can be fixed to a patient using a belt and/or by using an ultrasound patch. In some embodiments, this probe can be used to continuously monitor the flow to and/or in the target cavity space, optionally, to monitor a continuous flow, having the potential advantage of simplifying the monitoring procedure. In some embodiments, injector 102 is connected to pump 106, which flows the fluid through and/or out of injector 102. In some embodiments, using a pump allows to control and/or set the flow velocity, optionally according to the coordination with the settings of flow sensor 104. In some embodiments, using a pump allows controlling and/or setting a flow pattern of a non-uniform flow, having the potential advantage of providing a flow that varies in a controlled and/or known matter, optionally according to the coordination with the settings of flow sensor 104. In some embodiments, a desired flow velocity defines a desired flow pattern of a non-uniform flow, such as a pulse rate of a pulsatile flow. In some embodiments, a desired flow velocity and/or a desired flow pattern define pump settings, required for obtaining thereof, for example, the pump flow (e.g., pump speed) and/or pump pulse rate (or pulse frequency) and/or pump duty cycle. In some embodiments, the pump pulse frequency is about 1-10 Hz. For example, 2-6 Hz, 0.1-5 Hz, 4-10 Hz, or 4 Hz, or 5 Hz, or lower or higher or intermediate of pump pulse frequencies. In some embodiments, the pump and color Doppler ultrasound device 104 are synchronized, such that color Doppler ultrasound device 104 images the flow within the body, while the flow is provided using pump 106. In some embodiments, various types of pumps and/or other flow-generating systems, that can provide a flow having the required flow velocity and/or a pulse rate can be used as pump 106, such as a pressure source with a valve to control flow. In some embodiments of the invention, a flow source that provides both forward and backward flow and/or repetitive flow patterns is used, such as a reciprocating pump. Referring now to Figs. 1B showing a simplified block diagram illustration of a computerized system for assisting navigation in or to a target cavity space using a flow sensor, in accordance with some exemplary embodiments of the invention. In some embodiments, system 100 comprises a controller 108. In some embodiments, the controller synchronized between the fluid flow, injected by pump 106 through injector 102, and the operation of flow sensor 104, such as a color Doppler ultrasound device. In some embodiments, controller 108 coordinates between the fluid velocity and the settings of flow sensor 104 (e.g., a color Doppler ultrasound device). In some embodiments, controller 108 calculates a desired velocity flow and/or desired settings of flow sensor 104. In some embodiments, controller 108 calculates a desired flow pattern and/or flow properties, optionally considering the desired fluid velocity. In some embodiments, controller 108 calculates pump settings required to achieve a desired flow velocity and/or flow pattern. In some embodiments, controller 108 automatically sets pump 106 according to the calculation thereof. Alternatively, or additionally, controller 100 provides the settings and/or instructions for operating pump 106 . In some embodiments, controller 106 considers patient-specific and/or equipment-specific features when calculating the pump settings. In some embodiments, controller 106 uses a lookup table to select pump settings according to a patient specific and/or equipment specific properties. This customization has the potential advantage of controlling and/or improving the coordination between the flow properties and the color Doppler ultrasound settings which potentially further improve the detection and/or measurements of the flow. In some embodiments, controller 108 considers patients’ physical conditions, such as obesity and/or pregnancy, which affect pressures within body cavities. In some embodiments, controller 108 considers equipment features that can affect the flow. For example, length, inner lumen diameter, and/or material which can affect the friction of the flowing fluid therewithin. In some embodiments controller 108 considers fluid properties, such as fluid viscosity, which affect the resistance to flow thereof through injector 102. In some embodiments, controller 108 considers features of flow sensor 104 (e.g., color Doppler ultrasound device), fixed and/or adjustable. For example, controller 108 can consider and/or adjust factory default settings. In some embodiments, system 100 comprises a user interface 110 for obtaining patient-specific and/or equipment-specific features. In some embodiments, user interface 110 comprises a selection of a desired body cavity. Alternatively or additionally, each body cavity has a dedicated user interface 110 and/or a dedicated system 100. In some embodiments user interface 110 asks the user to provide the patient’s details, such as body weight, BMI, age, and/or pregnancy yes or no. In some embodiments, user interface 110 asks the user to provide equipment details, such as the injector’s type, manufacturer, and/or dimensions. In some embodiments, user interface 110 asks the user to provide details of the color Doppler ultrasound, such as manufacturer, and/or transducer frequencies range.

In some embodiments, controller 100 can further adjust the settings of flow sensor 104 and/or flow properties (e.g., flow velocity and/or flow pattern) to reduce imaging artifacts. In some embodiments, controller 108 performs a process of trial and error for adjusting the flow properties and/or the settings of the flow sensor, having the potential advantage of further improving the imaging. In some embodiments, system 100 comprises a pressure sensor 112 for sensing the pressure within the patient’s body. In some embodiments, controller 108 further adjusts the pump operation to achieve the desired flow velocity and/or pattern considering the patient-specific pressures within the body. In some embodiments, pressure sensor 112 is configured to measure the resistance to flow through and/or out of injector 102. In some embodiments, these resistance measurements can guide the operation of system 100. In some embodiments, as long the measured pressure is significantly different from the pressure that characterizes the target body cavity, system 100 holds from injecting the fluid into the body, and/or alerts the user to avoid injecting. This has the potential advantage of reducing and/or avoiding over-filing of the target body cavity and/or injecting fluid into an area other than the target cavity space. In some embodiments, resistance to flow through and/or out of injector 102, which can indicate the pressure inside the body, is evaluated based on the power consumption of pump 106. The higher the pressure inside the body (e.g., within an injection site), the more electricity pump 106 consumes to provide pre-set flow properties (e.g., flow velocity and/or pulse rate). This evaluation potentially reduces and/or avoids the need for a pressure sensor, having the potential advantage of reducing the complexity and/or costs of system 100. In some embodiments, system 100 is configured to visualize a fluid flowing within and/or out of a moving injector 102, optionally, toward the target body cavity. In some embodiments, controller 1can adjust the operation of pump 106 to achieve a desired flow pattern (e.g., velocity and/or pulse rate and/or duty cycle considering the velocity of the injector. In some embodiments, controller 108 may add backflow pulses for achieving a desired flow velocity and/or flow pattern, which allows the detection of the flow within the moving injector. In some embodiments, controller 108 comprises an analyzer configured for image analysis, such as an AI component (not shown) trained to process the flow sensor’s imaging, alternatively or additionally to transmitting the imaging to a screen. In some embodiments, the AI component is trained to recognize the imaged body cavity and to detect a fluid flow therewithin. This recognition potentially reduces and/or avoids the need for the anesthesiologist to recognize the imaged target cavity space, having the potential advantage of reducing identification errors and/or simplifying the procedure for less experienced anesthesiologists. In some embodiments, the AI component is configured to notify the user (e.g., anesthesiologist) of placement and/or misplacement of the flow within the target body cavity. In some embodiments, the AI component is trained based on clips of flow placed within the target cavity space and/or misplaced outside the target cavity space. In some embodiments, the AI component is trained to recognize a cavity target space in the color box. In some embodiments, the AI component is trained to determine placement and/or misplacement within the target cavity. In some embodiments, the AI component is trained to identify the place where flow is detected. In some embodiments, alternatively or additionally to imaging, the AI component can be used for processing non-visual data of color Doppler ultrasound and/or other Doppler ultrasound modulations. For example, analysis of M-mode output, pulse wave Doppler output, power Doppler output, and/or continuous Doppler output can be performed. In some embodiments, the AI component is trained to process the non-visual data and to conclude whether injector 102 is placed within a target cavity space. In some embodiments, the AI component is configured to combine Doppler ultrasound detection, optionally, color Doppler imaging, and pressure sensing. In some embodiments, the AI component performs pulse pressure analysis. In some embodiments, the AI component evaluates epidural placement by detecting a pressure that characterizes the epidural space and/or by detecting a pressure drop that indicates entrance into the epidural space, and evaluates that the measured pressure aligns with the Doppler ultrasound-identified location. In some embodiments, AI or other tool, such as statistical analysis is used to identify patterns and/or meeting of thresholds (for example, of pressure), to determine placement and/or problems. The patterns and/or thresholds can be optionally set ahead of time using experimentation.

In some embodiments, system 100 can be used with any standard ultrasound device that provides an Doppler ultrasound mode. In some embodiments, system 100 can be used with any pump that can generate a flow having a desired velocity and/or flow pattern. In some embodiments, injector 102 is provided with pump 106. Alternatively or additionally, pump 106 can be connected to other injectors. In some embodiments, pump 106 can adjust the setting thereof according to properties a selected injector. In some embodiments, flow sensor 104 comprises controller 108, and controller 108 is configured to connect to pump 106, optionally, by wiring, alternatively or additionally, wireless, for example, via WIFI and/or Bluetooth. In some embodiments, this connection allows controller 108 to define and/or adjust the setting of pump 106. In some embodiments, pump 106 comprises controller 108, and controller 1is configured to interface with flow sensor 104, optionally, by wired connection, alternatively or additionally, wireless, for example, via WIFI and/or Bluetooth. This interfacing allows controller 108 to define and/or adjust the setting of flow sensor 104. In some embodiments, controller 108 is configured to connect and/or interface with both flow sensor 104 and/or pump 106, defining and/or adjusting the setting of flow sensor 104 and/or pump 106. In some embodiments, system 100 is configured for manually adjusting the flow properties (e.g., fluid velocity, flow pulse rate and/or duty cycle) optionally, by the anesthesiologist. In some embodiments, system 100 comprises a mechanical and/or digital controller, for adjusting the settings of pump 106. In some embodiments, actuating the control modifies the flow velocity and/or flow pulse rate, optionally, in a controlled and/or gradual manner which allows to coordinate and/or to fine-tune the coordination between the flow and the settings of flow sensor 104. It should be noted that such modification may be carried out within a flow pulse, for example, modifying the maximum velocity of the pulse and/or between pulses. In some embodiments, the control is configured to be actuated while viewing the flow, for optionally fine-tuning the imaging of the injected fluid by adjusting the flow properties (e.g., flow velocity and/or flow pulse rate). For example, the control can be located on the probe of a Doppler ultrasound device. In some embodiments, the control can be actuated without using hands, for example, the control comprises a pedal, optionally placed on the floor and actuated by being pressed with a foot. Referring now to Figs. 2A-B showing a system for assisting navigation in or to an epidural space using a color Doppler ultrasound, where Fig 2A showing an injector and a color Doppler ultrasound device, interacting with a patient’s body, and Fig. 2B showing a pump, in accordance with some exemplary embodiments of the invention. In some embodiments, system 200 is a detail of an embodiment of system 100 ,shown in Figs. 1A-B. The same reference numerals have been used to denote parts that are similar to those described for system 100, with the prefix 2 replacing the prefix 1. In some embodiments, system 200 is configured to detect a flow to and/or within the epidural space. In some embodiments, system 200 is configured to detect a flow emerging from an opening of injector 102, indicating the location of this opening. In some embodiments, system 200 is can be used to detect flow expansion which can indicate fluid injection into the epidural space. In some embodiments, injector 202 comprises an introducer needle, such as a Tuohy needle, having an inner lumen shaped and sized for an epidural catheter to be inserted therewithin. In some embodiments, system 200 can view a fluid injected from the introducer needle and/or view a fluid injected from a catheter placed within the introducer needle, optionally, depending the uls transparency thereof. . Alternatively or additionally, system 200 is configured to view a fluid injected from the catheter after the introducer needle is removed. In some embodiments, the flow within injector 102 moves the injector so that the injector is visible using Doppler ultrasound device. In other embodiments, injector 200 comprises a needle used for epidural injection. In some embodiments, the flow sensor 104 is a color Doppler ultrasound device comprises a 2-5 MHz probe, potentially allowing to view the epidural space and/or flow within the epidural space (e.g., allows to set color box that includes the patient’s epidural space. In some embodiments, pump 106 is configured to provide a flow, optionally, a pulsatile flow having a maximum flow velocity in the range of 10-100 cm/sec. In some embodiments, the pulsatile flow potentially reduces over-filling of the epidural space, having the potential advantage of reducing and/or avoiding the risk of over-pressuring epidural space which might cause nerve damage. Referring now to Fig. 3 , showing a simplified flowchart of a method for reaching a target body cavity, using a system for assisting navigation in or to a target cavity space using a flow sensor, in accordance with some exemplary embodiments of the invention. At 302, a patient, undergoing a procedure that requires access to a cavity space, is selected. At 304, an injector (e.g., injector 102, 202) is inserted into the patient's body and toward a target body cavity. At 306, a fluid is injected through the injector while advancing the injector toward the target body cavity. In some embodiments, the fluid is injected during the advancement of the injector toward the cavity target, optionally, during a continuous advancement of the injector, alternatively or additionally during a stepped advancement of the injector. In some embodiments, the fluid is injected continuously, during a stepped and/or a continuous advancement of the injector. In some embodiments, the fluid is injected intermittently, during a stepped and/or a continuous advancement of the injector. In some embodiments, the fluid is injected during at least one step while the injector is advancing. Alternatively or additionally, the fluid is injected at least once, between steps of advancement, indicating the location of the injector at the end of an advancement (or retraction) step. At 308, the flow velocity and/or flow pattern is coordinated with settings of a flow sensor (e.g., flow sensor 104, 204), used to detect the injected fluid. This coordination has the potential advantage of improving flow detection and/or measurements. In some embodiments, the coordination is performed using a pump (e.g., pump 106, 206), that potentially provides a desired flow, optionally a flow that varies in a controlled and/or desired matter. In some embodiments, the operation of the pump and the flow sensor are synchronized, such that the controlled flow can be imaged by the flow sensor. In addition, injecting the fluid using a pump potentially frees a hand of the anesthesiologist from injecting the fluid and/or reducing the need for assistance.

At 310, the flowing fluid is viewed using the flow sensor, such as a color Doppler ultrasound device, during the advancement of the injector, optionally as described in Act 306. In some embodiments, the injector is advanced and the fluid is injected until recognizing placement at the target body cavity. Referring to Fig. 4 , showing a simplified flowchart of a method to assists navigation in or to a target cavity space, using a flow sensor in accordance with some exemplary embodiments of the invention. The method of Fig. 4 includes: Selecting a patient (402); Inserting an injector (e.g., injector 102, 202) into a target body cavity (404), optionally, as described in Fig. 3. Injecting a fluid through the injector into the target body cavity, using a pump (406); Coordinating the flow velocity and/or flow pattern of the injected fluid with the setting of a flow sensor (e.g., flow sensor 104, 204,) such as a color Doppler ultrasound device (408); Synchronizing the flow injection with the operation of the flow sensor (408); Detecting the injected fluid within the target body cavity using the flow sensor (412), to confirm the placement of the injector in the target body cavity (410); Referring now to Fig. 5A , showing graphs illustrating a timeline of a procedure for navigating in or to a target body cavity, in accordance with some exemplary embodiments of the invention. In some embodiments, the flow sensor (e.g., flow sensor 104, 204) is used to detect (e.g., view) a flow through and/or out of an injector (e.g., injector 102, 202), where the flow is generated by a pump (e.g., pump 106, 206). In some embodiments, the flow velocity and/or flow pattern generated by the pump and the settings of the flow sensor are coordinated, potentially enabling and/or improving the flow detection. In some embodiments, the pump operation and the flow sensor operation are synchronized, enabling the implementation of this coordination. In some embodiments, the fluid is injected into a patient’s body through the injector, and then the flow sensor is used to seek and/or detect the flowing fluid within the patient's body.

In some embodiments, the flow sensor is operated and a portion and/or a component thereof (such as an ultrasound probe) is placed on the patient's skin such that the color box (the area where evaluation of flow is performed) of the device includes the target body cavity, and then the pump is activated to inject the fluid through the injector and into the patient's body, such that the fluid can be detected (e.g., viewed) at the body target cavity and/or out of the body target cavity. In some embodiments, the flow sensor position is adjusted to detect the fluid within the patient’s body. In some embodiments, the color box is adjusted to include the sampling volume (e.g., the color viewed flow). It should be noted that each trapezoid in the time line of flow is an idealized presentation of a flow event. For example, such a flow event can include a single fluid pulse, more than one fluid pulses and/or negative and/or positive fluid pulse. In some embodiments, a fluid is injected through the injector after placing the injector’s tip within the body cavity, where the injector remains static, as shown for example in Fig. 5A. In some embodiments, fluid can be automatically injected (e.g., the pump is automatically operated) when the flow sensor detects that the injector remains static. Alternatively or additionally, a fluid is injected through the injector while the injector is advanced toward the target body cavity. In some embodiments, the injector advancement is stepped, and the fluid is injected by the pump and viewed by the flow sensors while the injector is advancing. Alternatively or additionally, the fluid is injected by the pump and viewed by the flow sensor between the steps, where the injector remains static, as shown for example in Fig. 5A. In some embodiments, the fluid is injected regularly over time by the pump, optionally in a pulsatile manner. For example, if the fluid is a medicinal substance such as an anesthetic, analgesic and/or other medicine, and the injection is aligned with a required dosage thereof. In other embodiments, the fluid is injected before and/or after operating the flow sensor and only as long as the flow sensor is used to detect the flow, having the potential advantage of reducing and or avoiding over-filling of the target body cavity and/or other body sites. In some embodiments, the pulsatile flow includes a back pulse every several pulses of the forward flow, allowing a total forward flow while controlling the amount and/or rate of fluid injected and the total forward speed.

In some embodiments, pulses of back-flow can be integrated into the pulsatile flow for adjusting the overall forward velocity with the settings of the flow sensor. In some embodiments, pulses of back-flow can be integrated into the pulsatile flow, for aligning the amount and/or rate of a therapeutic injected fluid with the administration requirements thereof. In some embodiments, pulses of back-flow can be integrated into the pulsatile flow for decelerating the fluid's overall forward velocity and/or be reduced for accelerating the fluid's overall forward velocity. In some embodiments, coherent detection can be employed to potentially enhance the signal-to-noise ratio and/or to improve flow measurements. In some embodiments, flow sensor 104 is synchronized with the pump operation such that measurements are taken when fluid is flowed to and/or in a target cavity space. for example, flow sensor 104 is synchronized to measure when a drop is expelled into the epidural space. In some embodiments, the measurements are synchronized to be taken a defined period before and/or after fluid is flowed to and/or within a target cavity space. In some embodiments, the measurements are taken when there is a change flow. In some embodiments, this synchronization allows the detection of movements of the cavity space walls and/or cavity space expansion, optionally, by viewing the flow within the changing volume of the target cavity, alternatively and/or additionally to sensing pressure in the cavity space. In some embodiments, the system (e.g., system 100 and/or 200) coordinates between the flow properties and the color Doppler ultrasound settings, to enable the flow to be detected by the color Doppler ultrasound transducer. This coordination has the potential advantage of reducing and/or avoiding aliasing which might cause to loss of directional and velocity information. In some embodiments, aliasing can result in spatial smearing of the image, which impairs the ability to distinguish where the flow is located. In some embodiments, reducing and/or avoiding aliasing has the potential advantage of improving the spatial imaging of the flow which can improve the detection reliability. In some embodiments, the system can use the tip location to set automatically the distance range which is used for imaging, and/or the system can use the last flow detection as an indication of what the distance range should be. In some embodiments, the system can use a low resolution imaging over whole image to detect flow synchronized with pump (e.g., coherent detection, as changes in flow will be coordinated with pump activity which is itself not coordinated with body movements) and then set the distance range for better resolution on that location where detecting flow synchronized with the pump. In some embodiments, the system coordinates between the fluid velocity and the PRF (pulse repetition frequency) and/or range of PRF of the color Doppler ultrasound transducer. Optionally, the PRF range, which is the Doppler sampling frequency (number of pulses within one second), can depend on the imaging depth of the color Doppler ultrasound transducer and/or the distance range being used. In some embodiments, the system determined a flow velocity to potentially reduce and or avoid under-sampling. This coordination between the fluid velocity and the PRF of the color Doppler ultrasound transducer has the potential advantage of reducing and/or avoiding aliasing which inert alia, impairs the possibility of determining the direction of fluid flow and/or causes imaging artifacts. In some embodiments, this ability to detect the direction of the fluid flow enables distinguishing between forward and backward flow and/or identifying fluid expansion within a body cavity which is characterized by flow in many directions. In some embodiments, detecting the direction of the fluid flow in the cephalad-caudal axis and/or dorsal-ventral axis comprises imaging including ultrasonography and/or PW/CW Doppler. In some embodiments, the system further adjusts the PRF of the color Doppler transducer. Without being bound to theory, the PRF has a range of possible values. In some embodiments, adjusting the PRF affects the velocity range window that can be detected. For example, the PRF can be increased to permit higher velocities to be displayed (the higher the PRF, the higher the scale of velocities that can be detected). This has the potential advantage of reducing and/or avoiding aliasing if a relatively high velocity is required. For example, when the injected fluid is an anesthetic, analgesic and/or other medicine, and the pulse rate thereof is dictated by the dose needed to be administered to a patient. In some embodiments, the PRF is adjusted according to the range of depths and/or depth of the target body cavity. For example, the PRF is typically inversely related to the depth range of the target body cavity, visualizing relatively thick cavities required a relatively low PRF, and visualizing relatively thin cavities allow a relatively higher PRF. In some embodiments, the system coordinates the PRF and the flow properties to obtain a high PRF as possible. Increasing the PRF has the potential advantage of improving imaging resolution. In some embodiments, the required fluid velocity is achieved by injecting the fluid using a pump. In some embodiments, using a pump potentially generates a controlled fluid velocity and/or pulse rate and allows achieving a desired fluid pattern. In some embodiments, the system determines pump settings which define the generation of a desired flow pattern. In some embodiments, the flow is pulsatile, optionally achieved by using a pulsatile pump. In some embodiments, the system sets a pulse rate of the fluid, alternatively or additionally to the velocity thereof. Without being bound to theory, the pulse rate of the flow defines the velocity of the fluid within injector 102, such that more frequent pulsations lead to higher velocity. In some embodiments, placement of an injector within a body cavity is recognized and/or confirmed by viewing a fluid expelled from the injector, at the emergence from an orifice thereof, within the target body cavity. In some embodiments, reducing and/or avoiding aliasing potentially enables the color Doppler ultrasound device to image the expelled fluid smaller than the imaged target body cavity, allowing to identify if the flow is within the target body cavity. In some embodiments, image processing is performed for aliasing detection. Since the timing of providing flow (e.g., the timing of operating pump 106) and/or the flow direction are controlled and/or known, unexpected flow behavior may indicate aliasing. In some embodiments, the settings of pump 106 (e.g., flow velocity) and/or of flow sensor 104 (e.g., PRF) can be adjusted to reduce and/or eliminate the aliasing. In some embodiments, placement of an injector within a body cavity is recognized and/or confirmed by functional identification of the flow properties within the body. For example, in some embodiments, placement within a target cavity is recognized by viewing an expansion of the fluid in the cavity space, which is less likely to occur in more dense tissues surrounding the epidural space, such as muscle tissues and/or intervertebral ligaments (ligamentum flavum and/or interspinous ligaments). Without being bound to theory, fluid expanding within a body cavity flows in a plurality of directions which can result in the view of more than one color and/or color scale. For example, fluid expansion can result in the view of a first color, such as red which indicates movement towards the transducer in addition to a second color, such as blue color indicates movement away from the transducer. The coordination, which potentially reduces and /or avoids aliasing has the potential advantage of reducing false-positive detection of movement towards and/or away from the transducer. Referring now to Fig. 5B , showing a graph illustrating an example of coordination between the fluid velocity and/or flow pattern and the color Doppler ultrasound settings in accordance with some exemplary embodiments of the invention. In some embodiments, the frame rate can be selected to be high enough for sensing porperties of flow such as velocity changes. In some embodiments, the coordination comprises optimization of the ultrasound frame rate (i.e., frames per second). In some embodiments, the frame rate is coordinated with the flow pattern of a non-uniform flow (e.g., pulsatile flow), as shown for example in Fig. 5B, for potentially improving the measurement detection. In some embodiments, the frame rate is set to reduce and/or avoid under-sampling. In some embodiments, the frame rate is set according to the Nyquist limit, where the sampling rate (frame rate) is set to be at least twice the frequency of the signal (e.g., fluid pulse frequency). This has the potential advantage of reducing and/or avoiding aliasing in imaging the flow pattern. In some embodiments, reducing and/or avoiding aliasing allows to visualize the pattern of a pulsatile flow, for example, to detect a Droplet flow by visualizing flickering sample volume and/or to detect alternately back and forward flow by visualizing two alternating colors. In some embodiments, the coordination comprises optimization of the color box size and/or position which affects the frame rate, (e.g., increasing the width of the color box consequently lowers the frame rate). In some embodiments, this optimization comprises setting a color box that includes the target body cavity, while the frame rate allows the visualization of the flow pattern. Referring now to Fig. 6A , showing a schematic side cross-sectional view of an injector placed within the epidural space, in accordance with some exemplary embodiments of the invention.

Referring also to Fig. 6Ba schematic example of a visualization of an injector placed within the epidural space using a color Doppler ultrasound device, in accordance with some exemplary embodiments of the invention. In some embodiments, system 200 is used to evaluate the location of the injector’s tip (e.g., injector 102, 202) within the patient body. In some embodiments, this evaluation is performed by visualizing the fluid as it emerges from the tip, such that the location of the fluid emergence indicates the location of the tip within the patient’s body. In some embodiments, the expelled fluid is viewed as a colorful dot and/or a smudge within the body, optionally, regardless of the probe (transducer) position. In some embodiments, the injector comprises an opening at the distal end of the tip such that a view of the expelled fluid indicates the location of the tip’s distal end. Alternatively or additionally, the injector comprises one or more lateral openings at a distance from the tip’s distal end, such that a view of the expelled fluid indicates the location of this lateral opening. This lateral opening potentially allows fluid emergence if the distal end is pushed against a tissue. Its noted that imaging of the flows may provide information about surrounding tissues, for example, elasticity and/or ability to move.

In some embodiments, a distinct region of interest (e.g., color box) is selected and viewed at the target body cavity, such as the epidural space. In some embodiments, the epidural space is imaged by the color Doppler ultrasound and recognized by the operator. The placement of the injector’s tip in the epidural space is conformed when the flow of the fluid expelled from the injector is viewed within the epidural space. In some embodiments, this assessment is performed by the anesthesiologist who is monitoring the screen of the color Doppler ultrasound. Alternatively or additionally, this assessment can be performed by system 200. In some embodiments, system 200 comprises a controller that has an AI component, trained to recognize the epidural space and to alert when a flow is viewed therewithin. In some embodiments, the flow pattern of the injected fluid is coordinated with the PFR of the color Doppler ultrasound transducer. This coordination potentially reduces aliasing and/or improves the resolution of the viewed flow such that the imaged fluid emerging into the epidural space is smaller than the dimensions of the target cavity (epidural space). This coordination has the potential advantage of reducing artifacts when imaging the flow, which may result in reducing and/or eliminating the risk of false-positive evaluation of placement in the epidural space. In some embodiments, placement in the epidural space can be recognized and/or confirmed by functional evaluating the flow within the body. The epidural space allows the fluid injected thereinto to expand in the cavity space unlike in other tissues such as the dense ligamentum flavum. As previously described, this fluid expansion can be identified by the color Doppler ultrasound presenting two colors rather than a single color and/or a color scale from a first color to a second color, where the first color represents fluid movement away from the transducer and the second color represents fluid movement toward the transducer. In addition, the view of the fluid expansion can be used to detect unwanted intravascular placement. In some embodiments, the expelled fluid is viewed to confirm that the tip of the injector (such as an epidural catheter) is not inserted into a blood vessel within the epidural space and/or at any other body site. Without being bound to theory, a fluid injected into a blood vessel flows with the blood flow in the vessel and does not expand. This has the potential advantage of reducing the risk of cardiac arrest which might result from the injection of a fluid into a blood vessel in the epidural space. In some embodiments, the color Doppler ultrasound can be used to view the path of the injector, such as an epidural catheter within the patient's body, optionally, from the puncturing site to the distal end of the injector. This imaging can be used to view if the injector’s tip (at the distal end of the injector) is placed within the epidural space. Potentially, the pulsatile flow within the catheter results in movements of the catheter within the patient's body such that the catheter becomes visible to the color Doppler ultrasound. In some embodiments, the flow pattern (e.g., velocity and/or pulse rate) is adjusted such that the injector can be viewed up to the target body cavity (e.g., epidural space). In some embodiments, the flow pattern and/or PRF are selected according to the depth of the target body cavity to enable visibility of the injector by the color Doppler ultrasound.

Referring now to Fig. 7A , showing a schematic side cross-sectional view of injectors misplaced out of the epidural space, in accordance with some exemplary embodiments of the invention. Referring also to Fig. 7B showing a schematic example of a visualization of injectors misplaced out of the epidural space using a color Doppler ultrasound device, in accordance with some exemplary embodiments of the invention. Injector A (e.g., epidural catheter A) is placed in the epidural space, and the orifice thereof is obscured by a bony component of the spine (unlike the injector shown in Fig. 6A). In some embodiments flow expelled from the catheter tip can be detected past the bony obstruction. In some embodiments, the probe of the color Doppler ultrasound device is repositioned to view the color signal from another angle. Injector B (e.g., epidural catheter B) is inserted beyond the epidural space, (deeper) into the subarachnoid space. In some embodiments, a fluid expelled from injector B is imaged by the color Doppler ultrasound in the subarachnoid space and is viewed outside of the boundaries of the epidural space, and deeper than the epidural space. This detection potentially leads to the withdrawal of the injector from the subarachnoid space, and optionally to re-positioning and/or re-inserting the injector. This withdrawal has the potential advantage of reducing and/or avoiding complications caused by insertion into the subarachnoid space, which is considered life-threatening. Injector C (e.g., epidural catheter C) is positioned off the epidural space, for example, within a bone (such as a vertebra) as shown for example in Fig. 7A, within muscle tissue, soft tissue and/or a ligament tissue or fascial plane. In some embodiments, the tip of injector C is placed before reaching the epidural space and/or mispositioned along the patient’s spine. In some embodiments, a fluid expelled from injector C is imaged by the color Doppler ultrasound away from the epidural space so the misplacement thereof can be detected. This detection has the potential advantage of reducing and/or avoiding inadequate pain relief, and/or ineffective delivery of medications. An additional potential advantage is reducing and/or avoiding patient discomfort and/or pain. In some embodiments, the view of the expelled fluid, which indicates the location of the injector’s tip can assist the anesthesiologist whether to reposition the injector or whether to withdraw the injector and re-insert. In addition, the view of the expelled fluid which indicates the location of the injector’s tip can assist the anesthesiologist with re-positioning the injector into the epidural. Referring now to Fig. 8 , showing a schematic side cross-sectional view of injectors misplaced out of the epidural space, in accordance with some exemplary embodiments of the invention. Injector D, is placed off the epidural space, for example, as shown in Fig. 8 at a tissue before reaching the epidural space. Injector F (e.g., epidural catheter F) is in the subarachnoid space as described for injector B, shown in Fig. 7A. Injector E (e.g., epidural catheter E) is positioned in the subdural space, located between the epidural space and the subarachnoid space. One of the risks of positioning the injector’s tip within the subdural space is that this misplacement is challenging to detect, without being bound to theory, due to the proximity to the epidural space and the subdural space being narrow. In some embodiments, a fluid expelled from injector E is imaged by the color Doppler ultrasound in the subdural space so the misplacement thereof can be detected. In some embodiments, the system (e.g., system 200) comprises an AI component trained to distinguish between the epidural space and the subdural space. In some embodiments, the positioning in the subdural space can be detected by visualizing a fluid expansion within the subdural space. Without being bound to theory, since the pressures within the epidural space, the subarachnoid space, and the subdural space are different, each has a distinguished fluid expansion pattern. Referring to Figs. 9A-B , showing a flowchart of a method for navigating in or to an epidural space, using a color Doppler ultrasound device, in accordance with some exemplary embodiments of the invention. At 902, a patient is selected. In some embodiments, the patient can be a pregnant woman, optionally, receiving epidural analgesia for labor. Alternatively or additionally, epidural analgesia and/or anesthesia can be used for managing the pain of patients during surgical procedures (such as thoracic and/or abdominal procedures). In some embodiments, the selected patient is a patient who does not meet the requirements to receive analgesia and/or anesthesia via the epidural space using commonly used methods. In some embodiments, the method enables providing epidural analgesia to patients with anatomical features which might create challenges for the anesthesiologist to find the epidural space. For example, patients who suffer from obesity and/or back problems (such as scoliosis), differences in the back structure anatomy, and/or patients after several failed attempts of insertion. At 904, an injector (e.g., injector 102, 202) is inserted into the epidural space, optionally as described later in this document. In some embodiments, the injector is an introducer needle comprising a lumen for the insertion of an epidural catheter therethrough. In some embodiments, the injector is an introducer needle bare of an epidural catheter and/or an introducer needle containing an epidural catheter. In other embodiments, the injector is an epidural catheter that remains in the epidural space after withdrawing the introducer needle In some embodiments, the injector is a needle for epidural injections. At 906, a fluid is injected into the epidural space through the injector, optionally, in a pulsatile manner. In some embodiments, the pulsatile flow is generated using a pump, optionally, a pulsatile pump. For example, in some embodiments, the fluid is injected in pulses with a volume of about 1 CC per second. For example, 1-CC per second, or 0.1-3 CC per second, or 0.5-1.5 CC per second, or 1.1 CC per second, or lower or higher or intermediate volumes per second. In some embodiments, the fluid is a test fluid. In some embodiments, the test fluid is liquid, such as a saline solution, a gas, such as air, and/or a mixture thereof. In some embodiments, the fluid is an anesthetic, analgesic and/or any other medical substance. At 908, the pattern of the pulsatile flow (e.g., velocity and/or pulse rate) is coordinated with the PRF of the color Doppler ultrasound transducer. This coordination has the potential advantage of reducing and/or avoiding aliasing and/or imaging artifacts. In some embodiments, the PRF is adjusted, within the possible range of values. Adjusting the PTF can be of a particular benefit if there are flow velocity requirements. For example, if the fluid is the administered analgesic, and the fluid velocity is dictated by the dose and frequency that should be provided to the patient. This adjustment has the potential advantage of further reducing and/or avoiding aliasing and imaging artifacts.

In some embodiments, the system (e.g., system 100, 200) comprises a pressure sensor (e.g., pressure sensor 112) and the coordination further comprises measuring the pressure within the patient’s body and adjusting the operation of the pump (e.g., injection rate) to obtain a desired flow pattern. In some embodiments, the system can measure the pressure within the insertion site and alert if the measured pressure does not characterize the target body cavity (e.g., epidural space). In some embodiments, this measurement is performed prior to fluid injection, having the potential advantage of reducing and/or avoiding injecting fluid into a body site other than the epidural space. At 910, the frame rate of the ultrasound transducer is optimized to the flow pattern of the fluid (e.g., velocity and/or pulse rate). This has the potential advantage of further improving the imaging resolution. In some embodiments, the system comprises a controller (e.g., controller 108) which interfaces between the pump and the color Doppler ultrasound device. At 912, the ultrasound probe is positioned on the patient skin. In some embodiments, the ultrasound probe is a flexible ultrasound probe. In some embodiments, the probe is positioned at and/or near the insertion point, optionally, at the interspace of insertion. In some embodiments, the positioning of the ultrasound probe can performed prior to the injection of the fluid. In some embodiments, a color box that includes the epidural space is set, optionally by the user, alternatively or additionally by controller 108. In some embodiments, the positioning of the color Doppler ultrasound is adjusted to view the flow. For example, if the injector is misplaced. For example, if the injector is an epidural catheter that has flexibility and can reach interspaces other than the interspace of insertion. In some embodiments, adjusting the color box leads to an adjustment of the frame rate, as previously described. At 914, the color Doppler ultrasound device is used to view the pulsatile flow within the body, during the injection of the fluid optionally, by a pump. In some embodiments, the operation of the color Doppler ultrasound device and the pump are synchronized in time.

In some embodiments, the fluid is visualized as it emerges from the injector, optionally, imaged as a colorful dot, indicating the location of the injector’s tip. Imaging the dot within the epidural space confirms placement of the injector’s tip (e.g., the injector’s opening) in the epidural space. Alternatively or additionally, the flow of fluid within the body is observed. A fluid expansion indicates placement of the injector’s tip within the epidural space, which is a potential space that can expand upon filing with fluid, rather than within a dense adjacent tissue and/or within a blood vessel. At 916, optionally, a backflow is generated within the injector, optionally, by setting the pump into suction mode. In some embodiments, the system generates a suction pulse every one or more pulses of injection. For example, the system generates a suction pulse every three pulses of injection. The alternating back and forward flow has the potential advantage of improving the visualization of the fluid emerging from the injector. In some embodiments, the suction reduces the amount of injected filing, potentially reducing the risk of over-filling the epidural space. In some embodiments, the fluid withdrawn reduces the pressure within the epidural space, having the potential advantage of reducing and/or avoiding the risk of causing nerve damage. In some embodiments, the suction, which generates a backflow (e.g., negative movement) potentially decelerates the flow forward pulses, having the potential advantage of improving control over the flow velocity. In some embodiments, this deceleration can be used to correct deviations from the desired flow pattern (according to the synchronization with the color Doppler ultrasound transducer). This deceleration has the potential advantage of improving the imaging resolution of a drop emerging from the injector. In some embodiments, the speed (e.g., the amplitude) of the backward pulses is less than the speed of the forward pulses. At 918, the flow is detected outside the epidural space. Alternatively or additionally, un- managing to detect the flow within the epidural space may indicate a misplacement of the injector’s tip. In some embodiments, the flow expelled from the injector is visualized outside the boundaries of the epidural space. In some embodiments, the fluid flow within the body is visualized, where a lack of fluid expansion indicates the fluid being expelled not within the epidural space.

At 920, optionally, the injector is repositioned and/or re-inserted. In some embodiments, if the viewed fluid, expelled from the injector, indicates that the injector is not deep enough, the anesthesiologist can further insert the injector, optionally, under visualization. In some embodiments, if the viewed fluid indicates that the injector is laterally diverted from reaching the epidural space, the anesthesiologist can withdraw and re-insert the injector. In some embodiments, if the view indicates that the injector was inserted too deep, the anesthesiologist can withdraw the injector up to the epidural space. At 922, an epidural placement of the repositioned and/or re-inserted injector is performed (by returning to act 906). At 924, the flow detection indicates on epidural placement of the injector. In some embodiments, the fluid expelled from the injector’s tip is viewed within the epidural space. In some embodiments, coordinating the flow velocity and/or pattern with the color Doppler ultrasound settings potentially reduces aliasing and/or imaging artifacts and/or improves resolution such that the color Doppler ultrasound device can image the fluid drops emerging from the injector in a region of the image smaller than the dimensions of the epidural space. This has the potential advantage of enabling to identified the fluid within the epidural space. In some embodiments, the diameter of the visualized fluid drop is no more than 0.5 cm, where the potential width of the epidural space is about 0.5 cm. In some embodiments, the diameter of the imaged drop (e.g, color dot) is about 3mm- 5mm. For example, 3-5 mm, 3.5-4.5 mm, 4-4.8 mm, or 3.8 mm, or 4.2 mm, or lower or higher or intermediate ranges or diameters. In some embodiments, the flow within the body is viewed, where an expansion of fluid indicates an epidural placement. In some embodiments, the injector is an introducer needle and after confirming the placement thereof within the epidural space, an epidural catheter is inserted through the introducer needle’s lumen. In some embodiments, the introducer needle is then withdrawn from the body while the epidural catheter remains in the epidural space. In some embodiments, the placement of the epidural catheter within the epidural space is confirmed as well as previously described, having the potential advantage of reducing and/or avoiding the risk of inserting the epidural catheter’s tip into a blood vessel within the epidural space which might result with the patient having a cardiac arrest. In some embodiments, the confirmation of the epidural catheter placement is performed prior to withdrawing the introducer needle. Alternatively or additionally, the confirmation is performed after withdrawing the introducer needle, which can potentially detect the misplacement of the epidural catheter caused by the needle withdrawal. In some embodiments, the injector is a needle for epidural injections. In some embodiments, the epidural placement confirmation is performed by injecting the medical substance of the epidural injection. At 924, optionally, the system can be used to monitor the placement of the injector (e.g., epidural catheter) during the administration of an anesthetic, during labor, and/or a surgical procedure. This monitoring can have a particular use during analgesia for labor since the movement of the pregnant woman can result in the removal of the epidural catheter from the epidural space. This monitoring can have an additional particular use during general anesthesia, where the patient generally cannot communicate with the anesthesiologist and report on changes in the effect of the anesthetic which can indicate on displacement of the epidural catheter. This monitoring can have an additional particular use during thoracic surgical procedures, where the insertion of an injector in the upper back can be more challenging. In some embodiments, the monitoring is performed by periodically injecting a fluid, using the pump, and viewing the flow thereof within the patient's body using the color Doppler ultrasound device. In some embodiments, the monitoring can be performed by injecting the analgesic and/or anesthetic substance using the pump, such that the flow of the substance into the epidural space can be viewed by the color Doppler ultrasound device, having the potential advantage of simplifying the monitoring procedure. In some embodiments, the anesthetic can be used during the confirmation procedure as well, having the potential advantage of reducing and/or avoiding the need for exchanging fluids.

In some embodiments, the system can further be used to detect epidural hematoma, describing bleeding around the spinal cord, for example, due to a blood vessel being injured during catheter insertion. In some embodiments, such hematoma causes changes in flow patterns around and/or within the epidural space which can be detected, optionally viewed by the color Doppler ultrasound device. In some embodiments, these changes in flow pattern result in pressure changes around and/or within the epidural space (e.g., changes in the resistance to flow within and/or out of the injector) which can be detected by the pressure sensor. In some embodiments, an AI component is trained to identify changes in flow patterns and/or pressure that characterize hematoma. At 926, the system can be used to follow up a patient. If a pregnant woman during labor complains of pain or excessive numbness, the anesthesiologist can evaluate the location of the injector by using the system. This evaluation has the potential advantage of being relatively quick and/or reliable. In addition, following -up the patient using the system potentially reduces and/or eliminates the need to perform a commonly used evaluation procedure, which is more time-consuming, endangers the patient, and/or exposes the anesthesiologist to the risk of a medical lawsuit. This procedure includes injecting a substance that is visible to a standard ultrasound device, for viewing thereof within the epidural space using a standard ultrasound device. This imaging is often unreliable and insertion of this substance into a wrong space can be fatal to the patient. Referring now to Fig. 10A-B , showing a flowchart of a method for reaching the epidural space by detecting a flow thereto, using a color Doppler ultrasound, in accordance with some exemplary embodiments of the invention. At 1002, a patient is selected, for example as previously described in Act 902. At 1004, the penetration location is determined. In some embodiments, when the patient is a pregnant woman in labor, the location of the penetration is typically on the lower back, while for patients undergoing a thoracic surgical procedure, the location is at the upper back. In some embodiments, the penetration location is determined by the feeling and/or experience of the anesthesiologist. Alternatively or additionally, the penetration location is determined by pre-scanning the epidural space using a standard ultrasound.

At 1006, the patient is punched at the determined penetration location optionally by using an injector (e.g., injector 102, 202). In other embodiments, the injector is an introducer needle, having a lumen for inserting an epidural catheter therewithin, such as a Tuohy needle. In some embodiments, the injector is an epidural catheter placed within an introducer needle and/or free thereof. In some embodiments, the injector is a needle for epidural injections (used to inject a substance into the epidural space without requiring a catheter and/or leaving a catheter in the epidural space. At 1008, the probe of the color Doppler ultrasound device is positioned on the patient’s skin, such that a fluid expelled from the injector’s tip can be visualized by the color Doppler ultrasound device. At 1010, the injector is advanced toward the epidural space. The injector can be advanced while applying the midline approach, the paramedian approach, and/or any other approach selected by the anesthesiologist. At 1012-1014, a fluid is injected through and out of the injector, and the flow expelled from the injector’s tip is visualized by the color Doppler ultrasound device. Viewing the expelled fluid over time indicates the injector's progression. In some embodiments, the fluid can be a test fluid such as a saline solution, a gas, such as air, a suspension, an emulsion and/or any mixture thereof. Alternatively or additionally, the fluid can be a medical substance such as a medicine, an anesthetic, and/or an analgesic. In some embodiments, the injector is progressing continuously and the fluid is injected and viewed while the injector is advanced, optionally in a continuous manner, alternatively, or additionally in an intermittent manner. In some embodiments, the injector is progressing in steps. In some embodiments, the fluid is injected and viewed during the steps (when the injector is advancing). In some embodiments, the fluid is injected and viewed between steps, while the injector is static. In some embodiments, the fluid is injected and viewed from the penetration point and up to reaching the epidural space. In other embodiments, the system comprises a pressure sensor that detects and/or monitors the resistance to flow out of the injector within the body and optionally notifies the user (e.g., anesthesiologist) if the measured pressure is too high and/or too low than the expected pressure within the epidural space. For example, relatively high pressure may indicate that the injector’s tip is still within the ligamentum flavum, and not within the epidural space. It is noted that the controller can use both pressure information and flow detection to evaluate placement and/or problems. In some embodiments, the system automatically ceases to inject the fluid when and/or while the measured pressure is too high and/or low relative to a pressure expected in the epidural space. In some embodiments, the system automatically activates fluid injection and visualization when and/or while the measured pressure is typical of the epidural space. At 1016, the flow pattern (e.g., velocity and/or pulse rate) of the injected fluid is coordinated with the settings of the color Doppler ultrasound transducer, as previously described in this document. In some embodiments, this coordination allows viewing the injected fluid using the color Doppler ultrasound. Additionally, this coordination has the potential advantage of improving the detection and measurements of the flow. In some embodiments, if the fluid is injected while the injector is advanced, this coordination further considers the motion of the injector toward the epidural space. In some embodiments, the advancement speed of the injector and/or the fluid velocity are set such that the overall progressing velocity of the flow is coordinated with the PRF of the color Doppler ultrasound device. Alternatively or additionally, the motion signal created by the advancement of the injector can be canceled. In some embodiments, alternatively or additionally to viewing a fluid injected through and/or out of an advanced injector, the velocity of an advanced injector can be coordinated with the setting of the color Doppler ultrasound device to enable visualization of the moving injector using the color Doppler ultrasound device. In some embodiments, this advancement in a stable and/or pre-set velocity can be performed using a robotic arm. In some embodiments, a controller of the system (e.g., controller 108) is interfacing with the robotic arm. In some embodiments, the desired flow pattern is generated by a pump. In some embodiments, the pump’s settings, such as pump velocity, pulse rate, duty cycle and uniformity of pump velocity or force, define the flow pattern (e.g., velocity and/or pulse rate). In some embodiments, the pump potentially frees the anesthesiologist from flowing the solution. for example by potentially reducing and/or avoiding the need to repress on a piston of a syringe, connected to the injector. This enables the anesthesiologist to hold the needle using one hand while positioning the ultrasound transducer using the other hand. This has the potential advantage of reducing the need for assistance and potentially allowing a single anesthesiologist to insert into the epidural space under vision. This may be considerably significant at times of low anesthesiologist availability in medical facilities such as delivery rooms and/or operating rooms. At 1018, optionally, a fluid is withdrawn as previously described in Act 916. In some embodiments, the velocity of the backflow is adjusted to the motion of the advanced injector. At 1020, the injector is placed within the epidural space and the advancement of the injector is ceased. In some embodiments visualizing the fluid emerging from the injector’s tip within the epidural space indicates reaching the epidural space. In some embodiments, visualizing an expansion of the fluid within the body indicates reaching the epidural space. In some embodiments, visualizing the injector’s path from the penetration point and to the epidural space indicates reaching the epidural space. At 1022, after reaching the epidural space, the placement therewithin can be confirmed and/or monitored by additional fluid injection and visualization thereof by the color Doppler ultrasound device, as previously described in Figs. 9A-B. In some embodiments, the injector is a needle for epidural injections. In some embodiments, the insertion of the needle into the epidural space is performed under vision using the color Doppler ultrasound device, where the color Doppler ultrasound device detects a fluid flowing into and/or within the patient’s body. In some embodiments, since a small amount of fluid and/or a low fluid velocity is required for navigating the needle into the epidural space, the procedure can be performed using the medical substance for the epidural injection. This potential reduces and/or eliminates the need to replace fluids, having the potential advantage of simplifying the procedure.

In some embodiments, when reaching the epidural space, placement confirmation can be performed, optionally by injecting an additional small amount of the medical substance. In some embodiments, after reaching the epidural space under vision and optionally confirming the placement within the epidural space, the medical substance is injected, optionally under vision as well. Referring to Figs. 11A-B , showing a flowchart of a method for navigating in or to a cavity space using backflow, in accordance with some exemplary embodiments of the invention. The method of Figs. 11A-B include: Selecting a patient, as previously described in Act 902 (1102); Placing an injector within a target body cavity, such as the epidural space, for example, as previously described in this document (1104); Injecting a fluid through and into the patient's body (1106); Withdrawing a portion of the fluid (1108); Detecting the backflow using a flow sensor (flow sensor 104, 204), optionally viewing the backflow using a color Doppler ultrasound device (1110); Optionally, coordinating the backflow velocity and/or pattern with the PFR and/or frame rate of the color Doppler ultrasound transducer, having the potential advantage of improving the detection of flow and/or reducing aliasing and/or imaging artifacts (1112); Identifying epidural placement by viewing the backflow within the epidural space using the color Doppler ultrasound device (1114); In some embodiments, Identifying epidural placement can be performed by evaluating the resistance to backflow and/or by assessing the amount of fluid that can be withdrawn. For example, the resistance to backflow while suctioning fluid from the subarachnoid space differs from the resistance to backflow compared to the epidural space. In some embodiments, a fluid injected into the epidural space expands within the cavity space such the amount of the withdrawn fluid is no more than the amount equivalent to a drop remaining on the injector’s tip. In some embodiments, the withdrawal of a relatively larger amount of fluid can indicate that the injector is misplaced outside the epidural space. For example, a fluid injected into a relatively soft tissue is less likely to expand therewithin, therefor a larger amount of fluid can be drawn back, compared to the epidural space. In another example, suctioning from the subarachnoid space may withdraw a relatively large amount of fluid due to the presence of the subdural fluid therewithin. In addition, withdrawn the CSF (cerebro-spinal fluid) can be identified, further indicating injector placement within the subarachnoid space. In some embodiments, high resistance to flow while injecting and/or withdrawing fluid, and/or inability to inject and/or withdraw fluid can indicate that the injector is misplaced outside the epidural space. For example, tissues such as the intervertebral ligaments (ligamentum flavum and/or interspinous ligaments) and/or muscle tissues are relatively dense and the high pressure therewithin may restrict fluid injection thereinto and therefrom. In another example, suctioning the epidural space after injecting 1 CC of fluid can withdraw back approximately 0.1 CC of the fluid., In another example, suctioning a muscle tissue can generate either lower or higher backflow relative to the epidural space. In some embodiments, since blood vessels are collapsible, an attempt to draw fluid from a blood vessel can cause a blood vessel to collapse, which can be identified by raising the resistance to suction. In some embodiments, since the epidural space is not likely to collapse under suction, an increase in suction resistance indicates that the injector tip’s is placed in a blood vessel, within and/or exterior to the epidural space. In some embodiments, high resistance to suction may indicate blockage and/or semi-blockage of the injector orifice(s), optionally after being placed within the epidural space. (1116). Referring to Fig. 12A-B , showing an exemplary pump of a system for navigating in or to a target body cavity, in accordance with some exemplary embodiments of the invention. In some embodiments, the system’s pump (e.g., pump 106, 206) can be for example a peristaltic and/or centrifugal pump. In some embodiments, the pump is connected to a syringe, which comprises a container that contains the injected fluid and a piston, that can be moved back and/or forth. In some embodiments, the syringe is connected to an injector (e.g., injector 102, 202). In some embodiments, the piston velocity back and/or forth is controllable. In some embodiments, the piston motion is controllable such that forward pulsating movement, backward pulsating movement, forward and backward cyclic movement, or any combination thereof can be obtained. In some embodiments, a pulsatile motion of the piston is controllable. In some embodiments, the size and/or speed of the pulse, the delay time between pulses, and/or the number of pulses that the piston makes back and forth can be adjusted. In some embodiments, the pulse size ranges from (0.01mm-L) where L is the length of the container (1220) which can also be replaced with a longer container. In some embodiments, as previously described, the system comprises a controller (e.g., controller 108) connected to the pump. In some embodiments, the controller can adjust the pump settings to obtain a desired flow pattern In some embodiments, the controller can be programmed so that it controls the movement of the piston in the manner required for the desired test so that the system can work completely autonomously without human intervention. In some embodiments, the pump comprises a pressure sensor (e.g., pressure sensor 112) which can monitor and/or control pressure developing within the container. In some embodiments, the pressure sensor is installed at the exit from the container. The pressure developing inside the cylinder can be controlled and monitored using a pressure sensor installed at the exit from the cylinder. In some embodiments, the pump is connected to a control system and/or a data storage system, so that data measured during the system operation is stored in the data storage system for real-time processing and/or for future use. In some embodiments, the system allows saving operating settings of the pump and allows the selection and modification of these operating settings during the performance of the system, by a user (e.g., anesthesiologist) and/or by the system’s controller. Additional procedures In some embodiments, the system and/or method for assisting navigation in or to a cavity space can be used during a peripheral nerve block procedure. In some embodiments, a peripheral nerve block procedure includes injecting a local anesthetic, analgesic, and/or other medicine near a peripheral nerve that controls sensation and/or movement of an area of the body. In some embodiments, this procedure required reaching a space or a potential space near the target peripheral nerve. In some embodiments, the system (e.g., system 100) can be used to assist in advancing an injector (e.g., injector 102) near a peripheral nerve, confirming placement near a peripheral nerve, and/or monitoring the placement near a peripheral nerve, as previously described in this document. In some embodiments, the system and/or method can be used for the two general types of nerve blocks, a single dose administration (e.g., one or more injections) and/or continuous administration, for example, by using a catheter, as previously described in this document. In some embodiments, the system and/or method are adjusted according to the type of block. In some embodiments, the transducer frequency range is selected based on the depth of the target peripheral nerve. Then, the PRF and the fluid velocity and/or flow pattern are coordinated to allow the detection of the fluid emerging from the injector to and/or in the space near a target peripheral nerve. In addition, this coordination potentially reduces and/or avoids aliasing of the visualized flow to and/or in the target space. In some embodiments, the frame rate is further optimized, as previously described in this document. In some embodiments, the pump is set to generate a desired flow velocity and/or flow pattern. In some embodiments, this setting considers the injector’s properties such as length, diameter, and/or material which affect the resistance to flow (e.g., friction). In some embodiments, different types of blocks require different injector lengths to reach near the nerve. In some embodiments, different types of continuous nerve blocks will use different catheters In some embodiments, the pump settings are adjusted according to the pressure within the space near the target peripheral nerve, for potentially providing a desired flow velocity and/or flow pulse rate. In some embodiments, reaching near a target peripheral nerve and/or confirming placement near the target nerve is detected by visualizing the flow expelled from the injector. In some embodiments, since detecting an injector’s tip near a target peripheral nerve can be challenging using other, commonly used methods, visualizing a fluid expelled from the injector’s tip, has the potential advantage of reducing and/or avoiding injector misplacement. In some embodiments, since the dimensions and/or potential dimensions of a space near a target peripheral nerve are relatively small, reducing aliasing by coordinating between the flow sensor settings and the flow properties, has the potential advantage of reducing and/or avoiding spatial smearing, allowing to locate the visualized flow within the boundaries of the target space. In some embodiments, alternatively or additionally, since the pressure within a target space near a peripheral nerve differs from the pressure surrounding thereof, the flow within the target space can be detected, indicating placement of the injector within the space near the peripheral nerve. In some embodiments, system 1comprises information regarding expected flow patterns and/or pressures within tissues and/or cavities surrounding the target peripheral nerve, which can be used for assessing placement near a target peripheral nerve. For example, if a space near a target peripheral nerve is surrounded by dense muscle tissues, fluid expansion can indicate reaching the space near the peripheral nerve. In some embodiments, the injection of the a fluid can be done with a foot pedal or any other external control having the potential advantage of improving the anesthesiologist's ergonomics. In some embodiments, the system and/or method for assisting navigation in or to a cavity space can be used during a surgical drain procedure. In some embodiments, the transducer frequency range is selected according to the depth of the drained site, then the flow properties and the flow sensor settings are coordinated. In some embodiments, the system and/or method can be used to confirm the placement of the drainer within the target space upon insertion. In some embodiments, the system and/or method can be used to monitor the placement of the drainer for detecting displacement, thereof during drainage. In some embodiments, monitoring the drainer placement can have a particular use during a procedure where the patient can move during the drainage, which might result in the withdrawal of the drainer and/or displacement thereof. For example, during draining fluids from a patient’s gallbladder and/ or kidney. In some embodiments, a fluid can be injected through the drainer, and the flow therefrom to and/or in the target space can be viewed. Injecting a fluid potentially allows for the detection of whether a lack of fluid withdrawal from the target space is due to its drying or the result of misplacement of the drainer. In some embodiments, the fluid is a test fluid, such as saline solution, air, and/or a mixture thereof. Alternatively or additionally, the fluid can comprise a medicine.

In some embodiments, a withdrawn fluid can be viewed. In some embodiments, the fluid backflow is the drainage passive flow. Alternatively or additionally, the fluid can be withdrawn using a pump. In some embodiments the visualized fluid is the fluid(s) to be drained from the target site, having the potential advantage of reducing and/or avoiding the need for fluid injection and/or simplifying the procedure. In some embodiments, the flow properties and/or flow sensor settings are adjusted according to the depth of the drain site. In some embodiments, this adjustment considers the length, diameter, and/or material of the drainer. In some embodiments, this adjustment considers the viscosity of the flowing fluid. In some embodiments, the suction backflow can be reversed to forward flow such that the drained fluid is injected back into the target site, and can be viewed flowing to and/or in the cavity space. using the drained fluid potentially reduces and/or avoids alternating fluids, having the potential advantage of simplifying the procedure and/or simplifying monitoring. In some embodiments, the system and/or method for assisting navigation in or to a cavity space can be used during an intravenous (IV) cannula (IV infusion) procedure, which includes inserting a thin, flexible injector (e.g., cannula) into a vein optionally for providing direct access to the vein. In some embodiments, the method and/or system can be used to confirm placement of the injector’s tip within the vein subsequent to inserting thereof, and/or for monitoring the placement (i.e position inside a blood vessel) of the injector for detecting displacement of the injector during the infusion. Using the method and/or system has the potential advantage of reducing and/or avoiding medical complications and/or side effects that result from misplacement of the injector. This may have a particular use in cases where inserting the injector into the vein is challenging, for example, when the patient is a child, typically having a relatively small and delicate vein, and/or when a patient is an elder, that may have a relatively fragile vein. In another example, patients’ medical and/or physiological conditions decrease vein visibility and/or accessibility, such as dehydration, obesity, history of IV drug use, Edema, coagulation disorder, and/or any other condition that can increase the difficulty of inserting the IV injector. In some embodiments, the insertion of the injector can be performed under vision, using a flow sensor such as a color Doppler ultrasound device as previously described in this document, having the potential advantage of reducing the time to access a vein, which may have a particular use in emergency situations. In some embodiments, the IV fluid can be used for visualizing a flow to and/or in the vein, having the potential advantage of simplifying the detection and/or monitoring procedure. In some embodiments, the IV pump can be used to inject a fluid, optionally, an IV fluid, in a manner that the fluid flow can be detected by a flow sensor, and/or in a manner that potentially improves the flow measurements. Using the IV pump has the potential advantage of reducing the process complexity and/or equipment costs. In some embodiments, using the IV pump and/or the IV fluid has a particular use when monitoring the placement of the IV injector, where the need for alternating fluids and/or pumps is reduced and/or avoided, having the potential advantage of simplifying the process of monitoring. In some embodiments, the system requires, optionally via a user interface (e.g., user interface 110) patient information which may influence the structure and/or properties of the target vein and/or the pressure within and/or surrounding the target vein. In some embodiments, the system requires patient's characteristics (such as age, weight, height), patient intravenous volume status (such as dehydration, intact or fluid overload), and/or introduction of diseases that can affect the veins (such as but not limited to heart problems, vascular problems, severe infection) In some embodiments, injector placement within a target vein can be identified by visualizing the injector’s path to the target vein. In some embodiments, the system and/or method are adjusted according to the IV infusion process. In some embodiments, the transducer frequency range is selected based on the depth of the target vein. Then, the PRF and the fluid velocity and/or flow pattern are coordinated to allow the detection of the fluid emerging from the injector to and/or in the target vein. In some embodiments, the frame rate is further optimized, as previously described in this document. Then the pump is set to generate the desired fluid velocity and/or flow pattern, where this setting considers the injector properties such as length, diameter, and/or material thereof. In some embodiments, the injected fluid viscosity is considered as well. In some embodiments, alternatively and/or additionally to identifying and/or monitoring placement within a vein by visualizing a flow to and/or in the target vein, misplacement and/or displacement can be identified using pressure detection. In some embodiments, measuring pressure within the body and/or resistance to flow that is not typical of a vein can indicate misplacement and/or displacement of the injector. In some embodiments, monitoring the placement of the injector can be performed by detecting pressure changes. In some embodiments, the placement of the injector within a target vein is first identified, optionally by flow visualization, and then the pressure measurements are calibrated based on the measured pressure within the target vein, such that change in pressure relative to the vein pressure indicates displacement of the injector. It is expected that during the life of a patent maturing from this application, many relevant a system and a method for navigating in or to a target body cavity will be developed; the scope of the term a system and a method for navigating in or to a target body cavity, using a color Doppler ultrasound is intended to include all such new technologies a priori. As used herein with reference to quantity or value, the term "about" means "within  10 % of". The terms "comprises", "comprising", "includes", "including", "has", "having" and their conjugates mean "including but not limited to". The term "consisting of" means "including and limited to". The term "consisting essentially of" means that the composition, method or structure may include additional ingredients, steps and/or parts, but only if the additional ingredients, steps and/or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure. As used herein, the singular forms "a", "an" and "the" include plural references unless the context clearly dictates otherwise. For example, the term "a compound" or "at least one compound" may include a plurality of compounds, including mixtures thereof. Throughout this application, embodiments of this invention may be presented with reference to a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as "from 1 to 6" should be considered to have specifically disclosed subranges such as "from 1 to 3", "from 1 to 4", "from 1 to 5", "from 2 to 4", "from to 6", "from 3 to 6", etc.; as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range. Whenever a numerical range is indicated herein (for example "10-15", "10 to 15", or any pair of numbers linked by these another such range indication), it is meant to include any number (fractional or integral) within the indicated range limits, including the range limits, unless the context clearly dictates otherwise. The phrases "range/ranging/ranges between" a first indicate number and a second indicate number and "range/ranging/ranges from" a first indicate number "to", "up to", "until" or "through" (or another such range-indicating term) a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numbers therebetween. Unless otherwise indicated, numbers used herein and any number ranges based thereon are approximations within the accuracy of reasonable measurement and rounding errors as understood by persons skilled in the art As used herein the term "method" refers to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the chemical, pharmacological, biological, biochemical and medical arts. As used herein, the term "treating" includes abrogating, substantially inhibiting, slowing or reversing the progression of a condition, substantially ameliorating clinical or aesthetical symptoms of a condition or substantially preventing the appearance of clinical or aesthetical symptoms of a condition. GeneralIt is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements. Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. It is the intent of the applicant(s) that all publications, patents and patent applications referred to in this specification are to be incorporated in their entirety by reference into the specification, as if each individual publication, patent or patent application was specifically and individually noted when referenced that it is to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting. In addition, any priority document(s) of this application is/are hereby incorporated herein by reference in its/their entirety.

Claims

1. WHAT IS CLAIMED IS: 1. A system for identifying a placement of an injector, within a body cavity comprising: A flow sensor; and A pump, configured to generate a fluid flow through and out of the injector, wherein the flow sensor and the pump are configured to be operated is synchronization, wherein the fluid flow can be detected by the flow sensor.

2. The system according to claim 1, wherein the flow sensor is a color Doppler ultrasound device.

3. The system according to any of claims 1-2, wherein the flow sensor is a color Doppler ultrasound device.

4. The system according to any of claims 2-3, comprising a controller, wherein the controller is configured to coordinate between flow properties and settings of the flow velocity sensor.

5. The system according to claim 4, , wherein the controller is configured to coordinate between a flow velocity and a PFR or a PFR range of the color Doppler and to determine a desired flow velocity and PFR value.

6. The system according to any of claims 4-5, wherein the controller is configured to adjust the PRF of the color Doppler ultrasound device according to a fluid velocity.

7. The system according to any of claims 4-6, wherein the controller is configured to adjust the frame rate of the color Doppler ultrasound device.

8. The system according to any of claims 4-7, wherein the controller is configured to determine pump settings according to the desired flow velocity.

9. The system according to any of claims 4-8, wherein the controller is configured to set the flow to alternate between forward-flowing and back-flowing and wherein the pump enables such a flow.

10. The system according to any of claims 4-9, wherein the pump is a reciprocal pump or peristaltic pump.

11. The system according to any of claims 4-10, wherein the pump is configured to generate a pulsatile flow coordinated with said flow sensor.

12. The system according to any of claims 4-11, wherein the controller is configured to set a flow velocity or a flow pattern which can reduce or avoid aliasing.

13. The system according to any of claims 4-12, comprises a pressure sensor, configured to adjust settings of the pump to maintain a desired flow velocity.

14. The system according to any of claims 4-13, comprises a user interface, configured for inputting patient-specific information.

15. The system according to any of claims 4-14, comprises a user interface, configured for inputting equipment-specific information.

16. The system according to any of claims 4-15, comprising a screen for visualizing the fluid expelled from a tip of the injector, around said tip, using said flow sensor.

17. The system according to any of claims 4-16, configured for visualizing the injector upon placement, within the target body cavity.

18. The system according to any of claims 4-17, wherein the controller is configured to set the flow velocity and the PRF so that the flow is localized on an image to within no more than 5 mm.

19. The system according to any of claims 4-18, wherein the controller is configured to coordinate between flow properties and settings of the flow velocity sensor such that the flow can be viewed within the body cavity.

20. The system according to any of claims 4-18, wherein the controller is configured to coordinate between flow properties and settings of the flow velocity sensor such that the flow can be viewed within the target body cavity and does not exceed beyond the target body cavity.

21. The system according to any of claims 15-20, configured for visualizing the injector while advancing toward the body cavity.

22. The system according to any of claims 1-21, configured for monitoring the injector placement within the body cavity, wherein the monitoring can be continuous or intermittent.

23. The system according to any of claims 1-22, wherein the body cavity is an epidural space.

24. The system according to claim 23, wherein the injector is configured for inserting into the epidural space, and wherein the injector is an introducer needle or a needle for epidural injection.

25. A method for detecting an injector to or within a target body cavity using a flow sensor, wherein the method comprises: providing a flow sensor for measuring fluid flow at a region of a tip of said injector; detecting a flow near the tip of the injector within the body, using the flow sensor; providing a system configured for synchronizing the flow with the flow sensor; and determining a placement of said injector based on a detection of the flow within the body cavity, using the flow sensor.

26. The method according to claim 25, wherein the synchronizing comprises coordinating between flow properties and settings of the flow sensor.

27. The method according to claim 26, wherein the flow sensor is a color Doppler ultrasound device, and wherein the coordinating comprises selecting a flow velocity according to a PRF range or a PRF value of the color Doppler ultrasound device.

28. The method according to any of claims 25-27, wherein the f flow is a pulsatile flow coordinated with said flow sensor.

29. The method according to any of claims 27-28, wherein the coordinating comprises adjusting a PFR of the color Doppler ultrasound device according to the flow velocity.

30. The method according to any of claims 27-28, wherein the coordinating comprises adjusting the frame rate of the color Doppler ultrasound device.

31. The method according to any of claims 26-30, wherein the providing comprises using a pump for generating the flow.

32. The method according to claim 31, wherein the using a pump comprising pre-setting the pump to generate a flow velocity according to said coordinating.

33. The method according to any of claims 25-32, wherein the detecting comprises visualizing the fluid expelled from a tip of the injector, around said tip.

34. The method according to any of claims 25-33, wherein said determining comprises identifying placement of the injector’s tip within the body by viewing the flow expelled from the tip of the injector, around said tip within a body cavity.

35. The method according to any of claims 25-34, wherein the determining comprises confirming placement in the target body cavity by viewing the flow within the body cavity.

36. The method according to claims 34 or 35, wherein the identifying comprises viewing the flow within the target body cavity and does not exceed beyond the target body cavity.

37. The method according to any of claims 25-36, comprises visualizing the fluid flow within the body and functionally assessing the flow, wherein visualizing fluid expansion indicates placement within a body cavity.

38. The method according to any of claims 25-37, wherein the providing comprises alternating between forward-flowing and back-flowing.

39. The method according to any of claims 34-38, wherein the target body cavity is an epidural space and the injector is an introducer needle or a needle for epidural injection, wherein the determining comprises determining placement in the epidural space.

40. The method according to claim 39, wherein the identifying comprises identifying epidural placement of an epidural catheter placed within the introducer needle.

41. The method of claim 40, wherein the identifying epidural placement of the epidural catheter comprises confirming that a tip of the epidural catheter is not within a blood vessel in the epidural space.

42. The method according claim 41, comprises monitoring the injector placement within the epidural space, wherein the monitoring can be continuous or intermittent.

43. The method according to any of claims 25-42, wherein the providing comprises providing a flow velocity or flow pattern which can reduce or avoid aliasing. Maier Fenster Patent Attorney G.E. Ehrlich (1995) Ltd. 35 HaMasger Street Sky Tower, 13th Floor Tel Aviv 6721407