JPH0135656B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic scanning ultrasonic diagnostic device that can obtain in-vivo tomographic information as well as blood flow velocity information. The purpose is to

BACKGROUND ART The ultrasonic Doppler method is conventionally known as a means of non-invasively measuring blood flow velocity in a living body.

This type of device is based on a technology that determines blood flow velocity from the frequency difference, that is, frequency shift, between transmitted ultrasound waves and waves reflected by blood cells or the like.

In recent years, in connection with this type of technology, a device capable of simultaneously obtaining tomographic information and blood flow information, that is, a complex ultrasonic diagnostic device, has been desired in the medical field. Conventionally, examples of such devices currently reported include cases in which separate transducers are used for the tomographic scanning method and Doppler method, and cases in which the same transducer is used for both methods. To briefly explain the configuration of the former device, a probe for ultrasonic Doppler measurement is attached to the tomography probe of the diagnostic device via an arm, and the position of both probes and the transmission and reception of the ultrasonic beam are controlled. The direction is detected by a potentiometer. Then, one probe obtains a real-time tomographic image,
The other probe is used to observe blood flow velocity from the Doppler displacement of ultrasound waves. This type of device is
This is very useful because it allows you to obtain two related pieces of information at the same time. However, with the above method, since the sound wave emitting surfaces of the two probes are separated, the passage area of the ultrasound beam for Doppler measurement cannot be completely visualized, so the Doppler ultrasound beam does not reach the target area reliably. I don't know if it's done or not. For example, when obtaining a tomographic image using a sector electronic scanning probe, the field of view at short distances is very narrow, so the disadvantage is that the area through which the ultrasound beam for Doppler measurement at short distances cannot be completely visualized. use. In general, the attenuation characteristics of ultrasonic waves in the human body vary greatly depending on the tissue. For example, the attenuation is very large in bones, lungs containing a large amount of air, and many tissues of the digestive system. If such tissue exists between the probe for Doppler measurement and the target area for Doppler examination, it will be impossible to obtain an effective echo signal from the target area, so it will be difficult to obtain a valid echo signal from the target area. It is necessary to make the Doppler ultrasound beam incident while avoiding tissue. However, in the case of the apparatus having the above configuration, the region through which the Doppler ultrasound beam passes cannot be completely visualized, so even if there is a tissue with high attenuation especially in a short distance region, it may not be possible to confirm it in the tomographic image. This drawback occurs because two separate probes are used, but as described below, the degree of this drawback varies depending on the tomographic image scanning method. That is, when the field of view is wide in a region close to the probe, the portion that cannot be displayed in the region through which the Doppler ultrasound beam passes is reduced.

At present, the typical electronic scanning methods are sector electronic scanning and linear electronic scanning, but since the sector method has a narrow inspection width at short distances, the linear method is considered to be suitable to address the above drawbacks. I can say that. However, in linear electronic scanning, the test width at short distances is also limited by the scanning width of the probe, which may cause problems for the following reasons.

Generally, the relationship between Doppler frequency shift and flow velocity obtained by an apparatus is expressed by the following equation.

Δ=2 _p Vcosθ/C (1) where Δ=frequency deviation, _p =radiation frequency of ultrasound, V=average flow velocity of blood, C=velocity of sound in tissue (approx. 1540 m/sec), θ=direction of blood flow is the angle formed by the Doppler ultrasound beam. Therefore, as shown in the first equation, the frequency shift is proportional to the cosine of the angle θ formed by the ultrasound beam and the blood flow direction, and is maximum when the two are parallel and can be measured accurately, and zero when they are orthogonal. Therefore, it becomes impossible to measure. For these reasons, it is considered desirable that the ultrasound beam be incident at an angle of 60 degrees or less with respect to the blood flow direction.

On the other hand, when Doppler examination is performed on important blood vessels in the abdomen, for example, the abdominal aorta, inferior vena cava, etc. are located deep and parallel to the body surface. When a Doppler ultrasound beam is incident on such a test area at an angle of 45 degrees to the surface from the end of a linear electronic scanning probe with a test width L, the Doppler ultrasound beam The passing area can be displayed up to depth L. In general, the test width L is about 10 cm or less, and there are also conditions that the shorter the scanning width of the probe, the better the acoustic coupling with the body surface. For the reasons mentioned above, for blood flow located at a certain depth,
It is difficult to say that the inspection area obtained by ordinary linear electronic scanning is appropriate. In order to solve this problem, it is necessary to be able to display a trapezoidal area that has a test width comparable to linear scanning at short distances and a test width comparable to sector scanning at long distances.

In order to satisfy this condition, multiple piezoelectric vibrators of the probe are arranged so that their sound wave emitting surfaces are convex, and a circuit similar to linear electronic scanning is combined to scan the direction of the ultrasound beam radially. The present applicant has proposed a method that has a certain width of inspection near the body surface and secures a field of view wider than the inspection width of normal linear electronic scanning in deep regions. FIG. 1 shows a probe of this type, and a complex ultrasonic diagnostic apparatus using it will be described below.

In the figure, 11 is an ultrasonic probe for tomography, 12
is an ultrasound probe for Doppler measurement, 2 is a subject, 21
22 is a blood vessel; 31 is N piezoelectric vibrators; 4 and 5 are first and second acoustic matching layers bonded to the front surface of the piezoelectric vibrator 31, respectively;
8 and 10 are connection lines, 91 is a group of electronic switches, 92
It is also an electronic switch. The method of driving the probe 11 in the non-Doppler mode is the same as in normal linear electronic scanning, and transmission and reception are selected by the switch group 91 so that a group of M (<N) transducers is moved little by little.

In the Doppler mode, the switch 92 selects the Doppler measurement probe. Ultrasonic waves emitted from a piezoelectric transducer array driven in a non-Doppler mode travel inside the subject 2 as shown by an arrow 6. The reflected signal 7 within the subject is received again by the same piezoelectric vibrator array,
It is connected to a display unit of the main body of the diagnostic apparatus, a Doppler signal detection circuit, etc. through the connection line 8, electronic switch 91, and connection line 10.

Since the probe 1 has an arc shape, the scanning area of the ultrasound signals and echo signals that are switched by electronic scanning and emitted and received into the subject is
It is not rectangular like the conventional linear scanning type, nor is it fan-shaped from the center of the probe part like the sector scanning type, but is radial from the center 11 of the arc of the probe 1 and the probe The scan area is divided by child positions.

When the above-mentioned probe is used, there is no loss of information at short distances as in the case of the sector electronic scanning method, and the detection area is relatively wide even at short distances. It also has many advantages, such as eliminating the need for large transmitting/receiving sections and adding sections as in the sector electronic scanning method, and allowing a simple transmitting/receiving section similar to that of the conventional linear electronic scanning method. However, the test width in this case is determined by the curvature of the probe, so in order to obtain a test width greater than linear scanning, the curvature of the probe must be increased. The close contact with the subject, especially due to the influence of the concave portion at the joint between the tomographic probe and the Doppler measurement probe, deteriorates, making it impossible to obtain a good image. In order to achieve good acoustic coupling with the subject, when the ultrasonic probe 1 is embedded in the subject's surface 21 as shown in Figure 1, surrounding organs are compressed and the blood vessels 22 are naturally curved and flattened. It is clear that blood flow measurement under such conditions is difficult.

All of the examples described above use a combination of a tomography probe and a Doppler measurement probe.

On the other hand, this device uses the same transducer for both the tomographic image scanning method and the Doppler method, improving the operability of the probe and accurately determining the direction of the Doppler ultrasound beam on the tomographic image. is also being considered. However, this method also has some drawbacks, as far as the ones currently in practical use are concerned. This limits the degree of freedom in design, such as selecting the Doppler ultrasound frequency in accordance with the maximum velocity of blood flow, in addition to the ultrasound frequency, and it may be difficult to accurately measure the Doppler frequency shift.

The present invention has been made in consideration of the above circumstances, and its purpose is to use a probe having separate ultrasonic transducers and transducers for tomography, and a transducer for Doppler scanning, The present invention provides a practical composite ultrasonic diagnostic device that enables Doppler measurement over a wide area within a subject. An embodiment of the present invention will be described in detail below with reference to the drawings.

Fig. 2 shows the basic configuration of the probe section adopting the present invention, Fig. 3 shows an ultrasonic probe using the probe section of Fig. 2, and Fig. 4 shows the basic configuration of the probe section adopting the present invention. , shows a block diagram of a composite ultrasonic diagnostic apparatus using the ultrasonic probe of FIG. 3. Hereinafter, the same parts as those in the previous figure are given the same numbers and the explanation will be omitted.

A feature of the present invention is that the scanning angle is expanded between the acoustic matching layer provided in front of each of the piezoelectric vibrator array for tomography arranged in a convex shape and the piezoelectric vibrator for Doppler scanning, and the subject. By using a probe equipped with an acoustic propagation medium, it is possible to obtain a wide range of tomographic images and Doppler information.Furthermore, good acoustic coupling can be obtained without deforming the surface of the subject, and Doppler super The objective is to keep the passage area of the acoustic beam within the wide tomographic image display area, and to select the optimum value for the direction of the Doppler ultrasonic beam or the setting of the high frequency according to the properties of the region to be examined.

As an embodiment of the present invention, a case where the scanning angle is enlarged will be described with reference to FIG. For example, if the subject to be examined is a human body, an acoustic propagation medium 25 made of a material such as silicone rubber whose sound speed is slower than that of the human body and whose acoustic impedance is approximately the same is used as an array of piezoelectric vibrators arranged in a convex shape as shown in the figure. 31 and a Doppler scanning transducer 32, the acoustic matching layers 4 and 5 are provided so that the contact portion with the subject 2 is substantially planar. In this way, the scanning angle of the ultrasonic wave is further expanded, and therefore it can be said to be more suitable for displaying the area through which the Doppler ultrasonic beam passes. In this case, the acoustic propagation medium 25 becomes an acoustic lens for expanding the scanning angle.

FIG. 3 shows the configuration of an ultrasonic probe using a transducer section having such a structure. In Figure 3, the first
As shown in the figure, a row of transducers 31 arranged in a convex shape
The driving method for the part is as explained in relation to Fig. 1.
Similar to normal linear electronic scanning, transmission and reception are performed on certain groups at the same time, and in non-Doppler mode the groups are moved little by little, and in Doppler mode they are controlled by a group of electronic switches 91 to select a specific group. Alternatively, the electronic switch 92 is switched to select the Doppler measurement transducer 32. As mentioned here, in the probe of the present invention, the traveling directions of the ultrasound beams transmitted and received from the transducer row for tomography are spread out radially, so the angle suitable for obtaining Doppler frequency shift is determined. In many cases, a region to be examined is scanned using a transducer, in which case a specific group of transducer arrays for tomography can be used for Doppler measurement. The ultrasonic waves emitted from the piezoelectric transducer array driven in this manner are further deflected by the acoustic lens 25 and travel within the subject 2 as shown by arrow 6. The reflected signal 7 within the subject 2 is received again by the same piezoelectric vibrator array, and is coupled to the display unit of the main body of the diagnostic apparatus through electronic switches 91 and 92.

In the above-described probe, the scanning area of the ultrasonic signals and echo signals that are switched by electronic scanning and emitted and received from the transducer array 31 into the subject is an arc-shaped area 26 centered on the point 27. becomes. This is a piezoelectric vibrator row 31 arranged in a convex shape.
This is because the scanning angle of the sound waves is expanded by the acoustic propagation medium 25 in front of the. Therefore, the display of the region 26 is trapezoidal or arc-shaped. In FIG. 3, the transducer 32 for Doppler measurement is composed of one concave transducer. The direction of the sound wave emission surface is determined by taking into account the position of the test site and the refraction at the boundary between the acoustic lens 25 and the biological surface. A plurality of vibrators arranged in a concave shape may be used instead of the concave vibrator. Alternatively, it is also possible to provide a scanning circuit for a plurality of transducers arranged regardless of whether they are concave or convex, and electronically control the direction of the ultrasound beam for Doppler measurement. In either case, the transducer section for tomography and the transducer section for Doppler examination are located in the same probe, so they can be placed close together, making it suitable for displaying the passage area of the Doppler ultrasound beam. It has a structure.

FIG. 4 shows the configuration of a composite ultrasonic diagnostic apparatus using an ultrasonic probe having the above-mentioned acoustic propagation medium 25. In the figure, 41 is a transmitter that drives a piezoelectric vibrator; When focusing ultrasonic waves, a phase control circuit for focusing is also included. Receiving section 42
Similarly to the transmitting section 41, when focusing is performed, it also includes a phase control circuit for focusing. In addition to this, the device also controls the timing of transmitting and receiving ultrasonic waves, and generates control signals for controlling electronic switches in Doppler mode and non-Doppler mode. A sensitivity correction circuit 44 for correcting sensitivity differences between lines, a non-Doppler signal processing circuit 45 for displaying received signals as a tomographic image, and a tomographic image and Doppler signal processing circuit 4
Display unit 4 for displaying the Doppler information output of 8.
6, and a Doppler signal detection circuit 47. The control unit 43 includes a Doppler scanning position control circuit that sets the ultrasonic beam at an arbitrary position of the tomographic transducer part of the ultrasound probe or the Doppler measurement transducer part, and a Doppler scanning position control circuit that sets the ultrasound beam direction at this position. Also included is a circuit that provides information on the angle formed by the surface of the object. When the blood flow direction is parallel to the surface of the subject, the blood flow velocity can be calculated from the frequency deviation using the angle information given here using equation (1).

Specific examples of the Doppler signal detection circuit 47 include a method using quadrature phase detection technology, and specific examples of the Doppler signal processing circuit 48 include a method using frequency analysis technology using discrete Fourier transform. Specific examples of both are explained in , so we will not discuss them in detail here.

Chihara et al., "Ultrasonic Pulse Doppler Blood Flow Meter Using a Microcomputer" IEICE MBE79-20 (1979) P53 In addition to the function of displaying conventional tomographic images, the display unit 46 also outputs the output from the Doppler signal processing circuit 48. It is also possible to display the Doppler information as, for example, blood flow velocity or in the well-known sonogram format.

As described above, the present invention includes a first vibrator section consisting of a plurality of piezoelectric vibrators arranged in a convex shape, and a
a second vibrator section consisting of one or more piezoelectric vibrator sections, and between the two piezoelectric vibrator sections and the subject, the speed of sound is lower than that of the subject, and the acoustic impedance is approximately equal to that of the subject. A probe having an acoustic propagation medium made of a material so that the contact portion with the subject is substantially flat, a tomographic image display device, a Doppler scanning position control circuit, a Doppler signal detection circuit, a Doppler signal processing circuit, It is a complex ultrasonic diagnostic device that is equipped with a Doppler scanning beam direction angle generation circuit, etc., and obtains tomographic image information and blood flow information, and has many features as shown below. That is, a single probe includes a tomographic transducer section and a Doppler measurement transducer, and has good operability. In addition, the tomographic image has a trapezoidal examination area suitable for displaying the area through which the Doppler ultrasound beam passes both near and far, ensuring that the Doppler ultrasound beam reaches the target area. suitable for checking. Furthermore, the technique of scanning an ultrasonic beam radially within a subject in order to obtain a trapezoidal test area does not require large transmitting and receiving sections or phase control. Furthermore, compared to a case in which a convex tomography transducer section and a Doppler measurement transducer are simply arranged and the sound wave emission surface of the probe has convex portions and concave portions, in the present invention, the sound wave emission surface of the probe It is equipped with an acoustic lens that is almost parallel to the body surface, and has good adhesion to the surface of the living body, so there is no need to worry about deforming surrounding organs by forcing it. Furthermore, the enlargement of the test area by this acoustic lens brings about a desirable effect on the display of the Doppler ultrasound beam passage area, making it possible to perform Doppler measurement over a wide area within the test subject. Furthermore, since the Doppler measurement transducer is not the same as the intra-sectional transducer, it is possible to select the Doppler ultrasound frequency or determine the beam direction in accordance with the properties of the examined region.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a convex ultrasound probe proposed by the present applicant, and FIG. 2 is a perspective view showing the basic configuration of an ultrasound probe in an embodiment of the present invention.
FIG. 3 is a general configuration diagram of an ultrasound probe according to the present invention, and FIG. 4 is a block diagram of a composite ultrasound diagnostic apparatus using the ultrasound probe of FIG. 3. DESCRIPTION OF SYMBOLS 1... Ultrasonic probe, 12... Ultrasonic probe for Doppler measurement, 2... Subject, 21... Subject surface, 22... Blood vessel, 31... Piezoelectric transducer, 32...
...Piezoelectric vibrator for Doppler measurement, 4...First matching layer,
5... Second matching layer, 8, 10... Connection line, 91,
92...Electronic switch, 25...Acoustic lens, 3
0...Ultrasonic beam, 41...Transmission unit, 42...
Receiving unit, 43...control unit, 44...sensitivity correction unit,
45... Processing section, 46... Display section, 47... Doppler signal detection circuit, 48... Doppler signal processing circuit.

Claims (1)

[Claims] 1. A first vibrator section consisting of a plurality of piezoelectric vibrators arranged in a convex shape, a second vibrator section consisting of one or more piezoelectric vibrators, and the first and second vibrations. an ultrasonic probe having an acoustic lens for widening the scanning angle, which is in close contact with the sound wave emitting surface side of the child part, the object side is substantially planar, and is made of an acoustic propagation medium whose sound velocity is lower than that of the object; means for sequentially scanning a first transducer section to obtain a trapezoidal or arc-shaped ultrasonic tomographic image; and Doppler scanning position control for driving the second transducer section to transmit and receive an ultrasound beam for collecting Doppler signals. a Doppler signal detection circuit that detects the reflected signal of this ultrasound beam to obtain a Doppler signal, a circuit that provides information on the ultrasound beam direction and the angle of the object surface at this position, and a Doppler signal detection circuit that uses this angle information to An ultrasonic diagnostic apparatus comprising: a processing circuit that analyzes signals; and a display section that displays processed Doppler signals.