JPH053872A - Ultrasonic probe for body cavity - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce the multiple reflection artifacts due to acoustic impedance mismatch, facilitate orientation, and reduce the S / N ratio. [Structure] A cap 36 made of synthetic resin, which serves as an acoustic window, is fixed to the tip of an insertion portion 9 that is inserted into a tubular body cavity such as a blood vessel. In the cap 36, a piezoelectric vibrator 40 and a vibrator holder 41 that form the signal converter 37 are rotatably installed. The piezoelectric vibrator 41 is positioned so as to emit ultrasonic waves in a direction perpendicular to the insertion direction. The vibrator holder 41 is connected to the motor 10 via the spring shaft 33. The spring shaft 33 is loosely inserted in a support spring 34 and a coating tube 35 that is closely adhered to the support spring 34. On the other hand, the taper portion 36b as a side wall of the cap 36 facing the piezoelectric vibrator 40 is tapered by inclining at a predetermined angle α.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a probe of an ultrasonic diagnostic apparatus for obtaining a tomographic image of a living body by using an ultrasonic signal, and particularly to obtain a tomographic image of a tubular body cavity such as a blood vessel or a digestive tract.
The present invention relates to an ultrasonic probe for body cavity having a tube (catheter) containing an ultrasonic transducer and inserting the tube into the tube.

[0002]

2. Description of the Related Art An ultrasonic diagnostic method in medical treatment has an advantage that there is no irradiation obstacle unlike the diagnosis using X-rays and that soft tissue can be diagnosed without a contrast agent. In addition to such advantages, in recent years, ultrasonic diagnostic technology for inserting a transducer into the body has become widespread due to higher frequency of electronic circuits and advances in fine processing technology of ultrasonic transducers. In particular, in the diagnosis of the digestive tract, an endoscopic approach in which a catheter containing a transducer is inserted into the digestive tract is becoming widespread in clinical practice. More recently, inserting such a catheter into a blood vessel,
Attempts have been made to obtain a tomographic image of an abnormal site on the tube wall.

As a probe of an ultrasonic diagnostic apparatus for diagnosing such a thin tube wall, there is one shown in FIGS.

The ultrasonic probe 101 shown in FIG. 6 is of a vibrator rotating type. This ultrasonic probe 1
In 01, a bottomed tubular cap 103 is integrally sealed and fixed to the distal end of a flexible catheter 102, and a transducer holder 104 is inserted into the cap 103. The oscillator holder 104 is rotatably supported by the bearing 105 inside the cap 103, and is inserted into the catheter 102 and has flexibility.
It is connected via 6 to the output shaft of a motor (not shown). The cap 103 is made of, for example, hard plastic, and functions as an acoustic window that is transparent to ultrasonic signals.

The vibrator holder 104 has a part of the outer peripheral surface thereof which is inclined by α degrees (for example, 10 degrees) with respect to the axial direction. The inclined surface 104a serves as an ultrasonic transducer. The piezoelectric vibrator 107 is fixed. The piezoelectric vibrator 107 is connected to a signal line (not shown), and the signal line is connected to the transmitting / receiving unit of the apparatus main body via a rotary transformer. The cap 10
In order to match the acoustic impedance inside 3,
An acoustic medium M such as physiological saline, water or oil is filled.

Therefore, the rotational force of the motor of the device is transmitted to the oscillator holder 104 via the spring shaft 106, and the piezoelectric oscillator 107 rotates integrally. Therefore, by exciting each vibrator of the piezoelectric vibrator 107 with a pulse electric signal group having a predetermined phase difference, an ultrasonic beam is emitted from the piezoelectric vibrator 107 in a direction perpendicular to the vibrator surface. , Is transmitted through the acoustic medium M and the cap (acoustic window) 103, and is radiated toward the tube wall of the living body. Therefore, mechanical radial scanning or sector scanning becomes possible. At this time, the emission angle and the incident angle of the ultrasonic beam are set to the cap 10.
It is inclined by a predetermined value α (10 degrees) with respect to the radial direction of 3.

As described above, since the ultrasonic beam is obliquely radiated and made incident, even if there is a mismatch in acoustic impedance between the acoustic medium M and the acoustic window 103 or between the acoustic window 103 and the subject, the boundary between them. The occurrence of multiple artifacts due to multiple reflection of the ultrasonic beam on the surface is reduced, and misdiagnosis can be prevented.

On the other hand, the ultrasonic probe 111 shown in FIG.
Is called a mirror rotation type. This probe 1
Reference numeral 11 indicates that a cap 103 is fixed to the tip of a catheter 102, a mirror 112 is supported inside the cap 103 by a bearing 105, and a piezoelectric vibrating element 107 is used as a holder with a thick portion at the tip of the cap 103. It is fixed vertically and inwardly. Mirror 11
The surface of the second element on the side of the vibrator 107 is cut obliquely, and the angle of the inclined surface has a value smaller than 45 degrees with respect to the radial direction of the mirror 112 by a predetermined angle α. The mirror 112 is connected to the spring shaft 106 similar to that shown in FIG. 6, and the piezoelectric vibrator 107 in a fixed state is connected to the apparatus main body by a signal line (not shown). The other configurations are the same as those in FIG.

Therefore, when the ultrasonic signal emitted from the piezoelectric vibrator 107 is reflected by the oblique reflecting surface of the mirror 112, the signal propagates in a direction that is obliquely displaced from the radial direction by a predetermined angle α. Therefore, by rotating the mirror 112 continuously or within a predetermined range, radial scanning or sector scanning of ultrasonic signals can be performed. Here, the reason why the ultrasonic signal is obliquely emitted is the same as that described above.

[0010]

However, in the above-mentioned ultrasonic probe, since the propagation direction of the ultrasonic beam is oblique with respect to the cap 103, that is, the acoustic window, the scanning cross section is shown in FIGS. 9 has a conical cross section as schematically shown in FIG. 9 (FIG. 8 shows how the conical cross section spreads, and FIG. 9 shows a scanning situation inside the blood vessel B). For this reason,
The operator scans a position deviated from the intended position, so-called orientation becomes difficult to attach, and since ultrasonic waves are obliquely incident on the lumen, it is difficult for the reflected ultrasonic signal to return. There is a problem in that the signal intensity from the region of interest is lowered and the S / N (signal / noise) ratio is lowered, so that a sufficient tomographic image cannot be obtained.

The present invention has been made in view of the above problems of the prior art, and when obtaining a tomographic image of a tubular body cavity, artifacts due to multiple echoes due to acoustic impedance mismatch can be reliably reduced. It is an object of the present invention to provide an ultrasonic probe for body cavity that can be easily oriented by an operator and can improve the S / N ratio.

[0012]

In order to achieve the above object, in the ultrasonic probe for body cavity according to the invention of claim 1, a torque transmission shaft capable of transmitting the torque from the drive source received at one end to the other end. And is fixed to the other end of the torque transmission shaft and capable of bidirectionally converting an electric signal and an ultrasonic signal and radiating the ultrasonic signal in a direction perpendicular to the axial direction of the torque transmission shaft. A signal conversion unit, a tube that includes the torque transmission shaft and rotatably supports the torque transmission shaft, and a tip of the tube that is sealed while the signal conversion unit is included. An enclosure formed of a member capable of transmitting a sound wave signal is provided, and the inside of the enclosure is filled with an acoustic medium, while the side wall facing the signal conversion portion of the enclosure is provided along the axial direction of the enclosure. Tilted.

In the ultrasonic probe for body cavity according to the second aspect of the present invention, the side wall of the enclosure is a wall whose diameter is gradually reduced toward the tip side of the enclosure. In the ultrasonic probe for body cavity according to the third aspect of the invention, the torque transmission shaft and the tube have flexibility.

[0014]

The output torque of the drive source is transmitted to the signal conversion unit via the torque transmission shaft to rotate or rotate the signal conversion unit. Therefore, the ultrasonic signal converted by the signal conversion unit is an acoustic medium,
The light is transmitted through the enclosure (acoustic window) and radiated into the torque transmission axis, that is, in the plane perpendicular to the axial direction of the enclosure. This allows
Radial scanning or sector scanning is performed in a plane perpendicular to the axial direction. In addition, the ultrasonic beam is almost perpendicularly incident and reflected on the wall of the blood vessel or the like into which the enclosure and the tube are inserted, and for the enclosure as an acoustic window, only the inclination angle of the side wall of the enclosure. Oblique incidence.

In particular, the probe enclosure according to the second aspect has a tapered shape that is easy to insert. Further, claim 3
In the probe described, both the torque transmission shaft and the tube are bent, so that the probe can be easily inserted even in a complicatedly curved body cavity such as a blood vessel.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. This embodiment is applied to a vibrator rotating ultrasonic probe for body cavity.

In FIG. 1, reference numeral 1 indicates an ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus 1 includes an apparatus main body 2 that forms a predetermined tomographic image by ultrasonic waves, and a body cavity ultrasonic probe 3 connected to the apparatus main body 2.

The ultrasonic probe 3 for the body cavity is the main body 2 of the apparatus.
It has a hand-side operation section 8 on the side and an insertion section 9 which is connected to the hand-side operation section 8 and is inserted into a tubular body cavity such as a blood vessel. Of these, the hand operation unit 8 has an electric motor 10 as a rotary drive source, and a connecting portion 11 that connects the output shaft 10a of the electric motor 10 and the insertion portion 9.

The electric motor 10 is, for example, a servomotor that rotates in response to a command electric signal from the main body 2 of the apparatus, and is provided with an angle detector such as an encoder for detecting the rotational position signal.

The connecting portion 11 has a first housing 20, an intermediate housing 21, and a second housing 22 which are sequentially provided from the electric motor 10 side and have a through hole at the axial center, and the through hole of the first housing 20. It has a hard shaft 23 disposed therein. The hard shaft 23 is formed in a substantially cylindrical shape, and the motor output shaft 10a is inserted and fitted in the proximal side of the hole at the center of the axial direction (referred to as the electric motor 10 side), and the bearing is located at the fitted position. 25
It is supported by the inner peripheral surface of the first housing 20 via. Tip side of the first housing 20 (refers to the insertion portion 9 side)
The inner peripheral surface and the proximal outer peripheral surface of the intermediate housing 21 are threaded, and both are axially connected by screwing. The proximal inner peripheral surface of the intermediate housing 21 supports the distal outer peripheral surface of the hard shaft 23 via a bearing 26 and an oil seal 27. Further, the intermediate housing 21
The outer peripheral surface on the tip side and the inner peripheral surface on the proximal side of the second housing 22 are screwed together, and both are axially connected. Therefore, although the three housings 20, 21, 22 are fixed, the hard shaft 23 can rotate integrally with the output shaft 10a of the electric motor 10.

A mounting chamber is formed inside the first housing 20 on the side of the motor 10, and a rotary transformer 30 for non-contact signal exchange is installed between the housing 20 and the output shaft 10a of the mounting chamber. Has been done. Further, an injection port 32 for injecting the acoustic medium M is formed in the middle of the intermediate housing 21 in a state of communicating with the internal through hole. As the acoustic medium M, as described above, physiological saline, water,
Use oil.

The insertion portion 9 serves as a catheter having a spring shaft 33 as a torque transmission shaft, a support spring 34 having a diameter larger than that of the spring shaft 33, and an inner diameter substantially the same as the outer diameter of the support spring 34. Coating tube 3
5, a cap 36 as an enclosure fixed to the distal end side of the covering tube 35, and a signal conversion section 37 provided inside the cap 36. Signal converter 37
Is a piezoelectric vibrator 40 as an ultrasonic transducer.
And a vibrator holder 41 that supports the piezoelectric vibrator 40. The outer diameter of the insertion portion 9 is formed to be about 1.5 mm to 10 mm depending on the diagnosis site.

Among them, the spring shaft 33 is, as shown in FIG. 2, two-layer springs 33a and 33b whose winding directions are opposite to each other.
Consists of The spring shaft 33 is loosely inserted into the through hole of the intermediate housing 21, and its proximal end is inserted into and fixed to the tip of the through hole of the hard shaft 23. The distal end of the spring shaft 33 is attached to the vibrator holder 41. It is fixed. Therefore, the hard shaft 2 is rotated along with the rotation of the motor output shaft 10a.
3 rotates, and the rotational torque is transmitted to the vibrator holder 41 via the spring shaft 33. The covering tube 35 is tightly covered around the support spring 34 so that the covering tube 35 has sufficient flexibility, but the circular sectional shape of the covering tube 35 is retained by the support spring 34. As shown in the drawing, the proximal side of the close-fitting cylinder body has an intermediate housing 2
The outer peripheral surface and the inner peripheral surface of the tip end portion of No. 1 are fixed, and the tip end side is fixed to the outer circumference of the cylindrical spacer 43. The outer periphery of the spacer 43 is further covered with the cap 36 so as to be flush with the coating tube 35, and the joint between the coating tube 35 and the cap 36 is sealed.

As shown in FIG. 2, the vibrator holder 41 has a long and slender columnar shape. The proximal shaft portion is loosely inserted into the through hole of the spacer 43, and at the position of the tip end side of the spacer 43. The inner peripheral surface of the cap 36 is supported via a bearing 44. Here, the support spring 34, the covering tube 35, the spacer 43, and the bearing 44 constitute the tube of the present invention.

A piezoelectric vibrator 40 is fixedly provided on a part of the side surface of the vibrator holder 41 near the tip, and the piezoelectric vibrator 40 and the cap 36 face each other with a gap. In other words, the ultrasonic radiation and incident direction of the piezoelectric vibrator 40 is substantially perpendicular to the axial direction, that is, the insertion direction of the cap 36 into the body cavity.

The entire cap 36 is made of, for example, synthetic resin capable of matching the acoustic impedance, and as shown in FIG. 2, a base portion 36a on the proximal side having the same diameter as the covering tube 35 and a substantially conical shape. Taper portion (side wall) 36 that has a cylindrical shape and rises integrally from the base portion 36a
b and a rounded portion 36c at the tip fixed to the tapered portion 36b. The taper portion 36b surrounds the piezoelectric vibrator 40, and the outer peripheral surface of the taper portion 36b has an inclination that becomes thinner toward the tip. The inclination angle α is set to 10 degrees in this embodiment. The tapered portion 36b of the cap 36 functions as an acoustic window through which ultrasonic signals come in and go out.

On the other hand, the acoustic medium M injected from the injection port 32 reaches the inside of the gap 36 through the gap between the members, and this acoustic medium M is held by the oscillator holder 41 (piezoelectric oscillator 40) and the cap 36. Is filled between. Further, a signal line (not shown) is connected to the piezoelectric vibrator 40, and the signal line passes through the inside of the vibrator holder 41 and the inside of the spring shaft 33 to reach the rotary transformer 30,
The rotary transformer 30 transmits and receives signals to and from the rotating side and the fixed side in a non-contact manner. The rotary transformer 3
Instead of 0, a slip ring may be used.

Next, the function and effect of this embodiment will be described.

The operator slowly inserts the insertion section 9 into a desired body cavity such as a blood vessel, and causes the tip portion, that is, the signal conversion section 37, to reach a desired diagnosis site in the body cavity. At this time, since the cap 36 located at the tip of the insertion portion 9 has a tapered shape, it is easier to guide to the target site as compared with the case where the tip end has a simple tubular shape.

In this state, when the electric motor 10 which receives a command from the apparatus main body 2 rotates, the rotational torque is generated by the rigid shaft 23 and the spring shaft 33.
And the holder 41 itself rotates. As a result, the piezoelectric vibrator 40 rotates so as to draw a circle in the insertion direction. At the same time, when the drive pulse signal is supplied to the piezoelectric vibrator 40 through the rotary transformer 30 and the signal line, the piezoelectric vibrator 40 emits an ultrasonic beam signal.

This ultrasonic beam is radiated perpendicularly to the insertion direction (that is, perpendicular to the tube wall), and the acoustic medium M
And, it vertically enters the tube wall through the cap 36 as an acoustic window as shown in FIG. On the contrary, the ultrasonic signal reflected from the tube wall reaches the piezoelectric vibrator 40 through the cap 36 and the acoustic medium M, and is converted into an electric signal. The converted electric signal is transmitted to the signal line and the rotary transformer 30.
The image is sent to the apparatus main body 2 through the above, and a predetermined tomographic image reconstruction process is performed. Therefore, mechanical radial scanning of ultrasonic waves can be performed by driving the piezoelectric vibrator 40 while continuously rotating the electric motor 10 in one direction, and
Mechanical sector scanning can be performed by driving the piezoelectric vibrator 40 while repeatedly rotating the electric motor 10 within a predetermined angle range.

Now, assuming that a tomographic image is obtained by performing mechanical radial scanning, the ultrasonic signal goes in and out substantially perpendicularly to the tube wall, so the scanning section is a conical section as in the conventional case (see FIG. 8). ), And a regular vertical section perpendicular to the insertion direction is obtained as shown in FIG. For this reason, it is easier for the operator to have orientation.
The positioning of the target portion is simplified, and when the tomographic image is reconstructed, the signal processing is simplified because the process of converting the tomographic image of the inclined surface to the tomographic image of the vertical surface is not necessary.

Further, since the ultrasonic beam is vertically incident on the tube wall, even when the incident intensity is set to be the same as the conventional one, the intensity of the reflected echo becomes larger than that in the case of oblique incidence, and S / The N ratio is improved. At the same time, the vertical incidence makes it easier for the ultrasonic beam to enter the deep portion of the tube wall, and the range that can be covered by the tomographic image is expanded.

Further, although vertical incidence is made on the tube wall as described above, oblique incidence (incident angle α is, for example, 10 degrees) is made on the inner and outer surfaces of the cap 36 as an acoustic window. In addition, the same effect can be obtained as when transmitting and receiving the ultrasonic signal obliquely from the beginning. In other words, it is possible to accurately exclude the state in which one ultrasonic beam is periodically reflected by the acoustic window due to the difference in acoustic impedance, thereby reducing artifacts due to multiple echoes and obtaining a highly reliable tomographic image. Obtainable.

The ultrasonic probe for body cavity according to the present invention is not limited to the vibrator rotating type probe described above, but may be applied to a mirror rotating type probe. FIG. 5 shows an outline of the signal conversion unit of the probe 50 (the same reference numerals are used for the same components as those in the above-mentioned embodiment). In the same figure, a cap 51, which serves as an acoustic window, has a taper portion (side wall) 51 whose diameter is reduced toward the tip as in the above-described embodiment.
The piezoelectric vibrator 52 is provided in a state of being fixed and having its radiation surface facing downward at the tip portion inside thereof. Further, inside the cap 51, a mirror 53 having a reflecting surface at an angle of 45 degrees with respect to the insertion direction is rotatably supported by a bearing 54. A flexible double-winding spring shaft 33 is connected to the mirror 53 as in the above embodiment. Therefore, when the rotational torque is transmitted to the mirror 53 via the spring shaft 33, the mirror 53 rotates, so that the ultrasonic beam emitted from the piezoelectric vibrator 52 is bent perpendicularly to the axial direction by the reflecting surface of the mirror 53. Then, the ultrasonic beam is transmitted and received. Here, the piezoelectric vibrator 52 and the mirror 53 form a signal conversion unit. As a result, the vertical incidence is made on the vessel wall such as a blood vessel and the digestive tract, and the oblique incidence is made on the acoustic window.

Further, in the above two embodiments, since a flexible spring shaft was used as the torque transmission shaft, a tomographic image of the digestive tract, blood vessels, etc. was obtained. Is not limited to, for example, a rectum or the like is simply used by using a rigid body as a torque transmission shaft,
A sector scanning probe may be used.

[0037]

The ultrasonic probe for body cavity according to the present invention,
The signal conversion unit is rotated or rotated by the torque transmitted via the torque transmission shaft, and the ultrasonic signal converted by this signal conversion unit is perpendicular to the axial direction through the acoustic medium and the enclosure (acoustic window). Since it is possible to perform radial scanning or sector scanning in a plane perpendicular to the axial direction in order to radiate in a uniform plane, the operator can easily orient, and compared to the conventional case of scanning in a conical section, positioning is possible. Post-processing of the obtained signal is facilitated. Further, since the ultrasonic beam is incident and reflected on the tube wall of the blood vessel or the like to be diagnosed substantially perpendicularly, the reflection intensity becomes higher than that in the case of oblique incidence when the same incident power is applied, and the S / N ratio is increased. As the ratio improves and the incidence becomes oblique to the enclosure as an acoustic window, multiple reflections due to the mismatch of acoustic impedance between this enclosure and its inside and outside can be accurately eliminated, and the multiple echo Since it is possible to prevent the occurrence of artifacts due to the, the reliability of the reconstructed tomographic image is high.

In particular, the ultrasonic probe for body cavity according to the second aspect of the present invention has a tapered distal end portion, which facilitates insertion into a tubular body cavity. Further, in the ultrasonic probe for body cavity according to the invention of claim 3, since the insertion portion composed of the torque transmission shaft and the tube bends,
It can be easily inserted into a tubular body cavity having a complicated conduit such as a blood vessel.

[Brief description of drawings]

FIG. 1 is a sectional view in which a part of an ultrasonic probe for body cavity according to an embodiment of the present invention is omitted.

FIG. 2 is an enlarged cross-sectional view of a tip portion of the ultrasonic probe shown in FIG.

FIG. 3 is an explanatory view showing a propagation direction of an ultrasonic beam from a piezoelectric vibrator.

FIG. 4 is an explanatory diagram illustrating a scanning section.

FIG. 5 is a schematic cross-sectional view showing the structure of the tip portion of the ultrasonic probe for body cavity according to another embodiment of the present invention.

FIG. 6 is a schematic cross-sectional view of a tip portion showing an example of a conventional ultrasonic probe for body cavity.

FIG. 7 shows another example of a conventional ultrasonic probe for body cavity,
The schematic sectional drawing of a front-end | tip part.

FIG. 8 is an explanatory diagram illustrating a shape of a conventional scanning section.

FIG. 9 is an explanatory diagram showing a state of a probe inserted into a blood vessel.

[Explanation of symbols]

3 Ultrasonic probe for body cavity 10 electric motor 23 Hard shaft 33 Spring axis 34 Support spring 35 coated tube 36 cap 36b taper part 37 Signal converter 40 Piezoelectric vibrator 41 oscillator holder 43 Spacer 44 bearing 50 Ultrasonic probe for body cavity 51 cap 51b taper part 52 Piezoelectric vibrator 53 mirror 54 bearing M acoustic medium

Claims (3)

[Claims] 1. A torque transmission shaft capable of transmitting a torque from a drive source received at one end to the other end, and a torque transmission shaft fixed to the other end of the torque transmission shaft and capable of bidirectionally transmitting an electric signal and an ultrasonic signal. And a signal converter that radiates the ultrasonic signal in the direction perpendicular to the axial direction of the torque transmission shaft, and the torque transmission shaft is included and the torque transmission shaft is rotatably supported. A tube and an envelope formed by a member capable of transmitting an ultrasonic signal while sealing the tip of the tube in a state where the signal conversion unit is included, and filling an acoustic medium inside the envelope. On the other hand, the ultrasonic probe for body cavity, wherein the side wall of the envelope facing the signal conversion portion is inclined along the axial direction of the envelope. 2. The ultrasonic probe for body cavity according to claim 1, wherein the side wall of the enclosure is a wall whose diameter is gradually reduced toward the tip side of the enclosure. 3. The ultrasonic probe for body cavity according to claim 1, wherein the torque transmission shaft and the tube have flexibility.