JPH04297248A - Medical ultrasonic system - Google Patents

Abstract

PURPOSE:To provide a mechanism which allows an intense sound wave irradiation by enabling the checking to see if a focusing intense sound wave is focused on a target treatment area or object accurately as collimated in a focusing sound wave treatment. CONSTITUTION:A transmitting output of a focusing intense sound wave transmitter is allowed to be modulated and a component of an output modulation frequency of the transmitter is extracted and displsyed from a received signal of an ultrasonic pulse transmitter/receiver with a scannable directivity constituting a part of the system. A focusing intense sound wave is made to overlap a pulse echo image by the transmission with the ultrasonic pulse transmitter/ receiver and displayed, thereby enabling the checking to see if the focusing intense sound wave is focused accurately on a target treatment area or object.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic aiming monitoring mechanism in convergent sound wave therapy suitable for the treatment of malignant tumors, stones, and the like.

0002

[Prior Art] Stone crushing treatment and malignant tumor treatment devices using convergent high-intensity sound wave irradiation are minimally invasive treatment methods that do not involve surgery, and improve the quality of life of patients after surgery.
It is expected that its social value will continue to increase in the future as a treatment method that values FE).

[0003] In the case of treatment using such convergent high-intensity sound wave irradiation, it is extremely important for safety to correctly aim the convergent high-intensity sound wave at the treatment target area. In line with this purpose,
U.S. Pat.
21730, a device in which an ultrasonic probe for imaging is incorporated in a transmitting aperture for ultrasonic waves or shock waves is conventionally known. Such devices use sound waves that are refracted in the same way in the living body both to produce a therapeutic effect and for aiming and monitoring, so this self-alignment makes it possible to keep aiming errors small. There is a theoretical advantage that it can be done.

0004

[Problems to be Solved by the Invention] The above technology has made it possible to perform convergent sound wave treatment using aiming that can be expected to have a small aiming error in principle. In terms of treatment safety, it is highly desirable to be able to irradiate powerful sound waves while confirming that the target is correctly focused. It is an object of the present invention to provide a mechanism that makes this possible.

[0005]

[Means for solving the problem] When a difference in sound wave energy density occurs before and after an object is sandwiched due to the sound waves being reflected, absorbed, or scattered by objects in the medium, the object has a high sound wave energy density. is subjected to pressure that acts from high to low, so-called radiation pressure. The displacement of the living body due to this radiation pressure is completely negligible when a solid organ such as the liver is irradiated with a sound wave having a time average power as small as that of an ultrasonic diagnostic device. however,
If the power of the sound wave is large, as in a shock wave lithotripter, and the sound wave reflectivity of the object to be aimed at is large, such as a stone, the displacement of the object due to this radiation pressure will be large enough to be measured. In addition, although the sound wave reflection rate is not as high as that of a stone, parenchymal organs such as the liver have a considerably high ultrasound absorption rate, so they cannot be irradiated with focused ultrasound waves with a high time-average power, such as those used in the treatment of malignant tumors. Then, the displacement near the focal point due to radiation pressure becomes large enough to be measured. The displacement of the object to be aimed at due to this radiation pressure can be measured by applying a modulation method to the ultrasonic pulse echo method.
This method can be used as a means to confirm that the focused high-intensity sound waves are properly focused on the treatment target area.

[0006]

[Operation] The displacement of stones due to the radiation pressure of the sound waves irradiated by the shock wave lithotripter is so large that it can be easily observed in the moving images using the above-mentioned conventional aiming and monitoring ultrasonic imaging function. It is known that it can reach the order of mm. Therefore, according to the measurement method in which the modulation method is applied to the ultrasonic pulse echo method of the present invention, displacement can be measured even if the intensity of the convergent shock wave is significantly reduced.

It is necessary to explain in some detail how much displacement can be obtained in the case of other real organs such as the liver and mammary glands. Let us consider the case where a focal spot with an azimuth direction diameter of 2 to 4 mm and an acoustic power density of about 100 W/cm2 is formed in a parenchymal organ as described above using focused ultrasound waves with a frequency of 0.5 to 1 MHz. Since the attenuation coefficient of ultrasonic waves of the above frequency in the parenchymal organ is about 10%/cm, the tissue in the focal spot is 0.1N/cubic cm.
receives a body force of a certain magnitude. Assuming that the shear modulus of the parenchymal organ is 10 N/cm2, and assuming that the tissue 10 cm away from the focal spot in the azimuth direction is not displaced as a boundary condition, the tissue located at the focal spot is 0.1 mm
It is estimated that the amount of displacement will vary. Further, since the density of living tissue is approximately 1 g/cm3, the time required for the displacement near the focal point to become constant after ultrasonic irradiation at a constant focus is started is estimated to be 1 to 100 msec.

[0008] In order to detect the displacement caused by the convergent sound wave irradiation as described above with high sensitivity, an imaging ultrasonic pulse transmitting/receiving mechanism is used to measure reflected echo signals from the tumor tissue or stone to be aimed at. Then, the fluctuation component of the reflected echo signal due to turning on/off or increasing/decreasing the irradiation output or cyclically changing the transmission focus, that is, the component of the on/off cycle or increase/decrease cycle, or the component of the focus change cycle. Extract and measure.

[0009] As in the case of the parenchymal organ described above, it is difficult to detect 0.1 m with the conventional method because it is buried in non-variable components.
Even relatively small displacements on the order of m can be measured using this method of extracting the fluctuation component due to modulation of the focused irradiated sound waves, and the focused powerful sound waves can be accurately focused on the treatment target area. You can confirm that In addition, even in the case of stone fragmentation, prior to the main irradiation of the convergent shock wave, preliminary irradiation is performed at a lower intensity so that side effects will not be a problem even if the focus is slightly shifted. After confirming that the target is correctly focused on the target, the main irradiation can be performed with high intensity.

0010

Embodiments Hereinafter, embodiments of the present invention will be explained in detail with reference to FIGS. 1 and 2.

FIG. 1 shows a block diagram of an embodiment in which an array type transmitter is used as the convergent high-intensity sound wave transmitter and a differential method is used as the method for detecting the modulation component of the ultrasonic pulse echo signal. In addition, Figures 2(a) and 2(a) show the top and side views of the convergent strong sound wave transmitter incorporating the ultrasonic pulse transducer shown in the figure.
Shown in b).

This array type convergent strong sound wave transmitter 1 has a geometric focus in order to enable scanning of the strong sound wave focus with the minimum number N of transmitter elements. Geometric focus is provided by arranging the transmitter elements 1-1 to 1-N on a light alloy spherical shell. The light alloy spherical shell 5 is responsible for effective heat dissipation from the transmitter element, acoustic matching between the transmitter piezoelectric element and the coupling fluid, and also serves as a ground electrode for the piezoelectric element. Based on the control by the strong sound wave transmission circuit 11 synchronized by the main control circuit 10, the strong sound wave transmission output is turned on and off.
Output modulation such as off, increase/decrease, or even cyclic focus scanning is performed. A relatively large displacement can be obtained by setting the output modulation period to approximately 1 msec or more in consideration of the mechanical time constant of the irradiation target biological tissue.

The transducer 2 shown in FIGS. 1 and 2 has basically the same form as a normal sector scan type array transducer for pulse echo imaging, and has an acoustic matching layer 6. It is equipped with Part (b) of FIG. 2 shows a transparent view of the light alloy spherical shell 5 and the acoustic matching layer 6, and the acoustic coupling material has been omitted from FIG. 2 to avoid complication of the diagram. .

The pulse echo signal obtained by the transducer 2 is used not only for normal pulse echo image formation, but also for differential image formation synchronized with strong acoustic wave modulation. The echoes received by the transducer 2 and the transceiver circuit 13 are given a delay time for focusing in the reception focus circuit 14, are added together, and are stored in the memory circuit 2.
Temporarily recorded in 0-1 and 20-2. Recording in the memory circuit is performed in synchronization with the modulation of the powerful sound wave transmitted by the wave transmitting circuit 11, and records echo signals in a time phase that can be regarded as non-displacement at 20-1, and echo signals in a time phase in which a relatively large displacement can be obtained. signal 2
Record 0-2. The signal recorded in the memory circuit 20-1 is directly input to the display circuit 16 and displayed as a normal ultrasonic pulse echo image, while the signal recorded in the memory circuit 20-1
The difference with the signal recorded in 2 is calculated by the difference circuit 15, inputted to the display circuit 16, and displayed as a difference image.

There are two methods for detecting the echo signal: one method is to perform it in the reception focus circuit 14 after focus processing, and the other method is to perform it in the display circuit 16. The latter requires a larger capacity memory circuit 20, but provides higher sensitivity to displacement in the depth direction. Further, in order to make the difference image easier to use for checking aiming, the difference image is superimposed on a normal ultrasonic pulse/echo image and displayed with different display color tone and display brightness characteristics. Furthermore, even when harmonics are generated by convergent powerful sound waves based on cavitation or nonlinear propagation phenomena and are received by the transducer 13, this can be detected and displayed with greater emphasis through the above-mentioned differential processing. .

[0016] In the above, only an example in which an array type transmitter is used as a convergent strong sound wave transmitter is shown, but the present invention can also be applied to a case where a single focus type transmitter is used. . However, in this case, as a method of modulating the convergent high-intensity sound wave irradiation output, a method of turning on/off or increasing/decreasing the irradiation output can be similarly used, but a method of cyclically changing the transmission focal point can be used. It is difficult.

[0017] In addition, in the above, only an example in which the differential method is used as a method for extracting a fluctuation component corresponding to modulation of irradiation output from a reflected signal of a target biological tissue or object obtained by an ultrasonic pulse transmitting/receiving mechanism is described. Although shown, Fourier analysis can also be used. That is, from the reflected signal,
Extract the Fourier component with a frequency equal to the modulation frequency. Extracting modulation and in-phase components in the Fourier analysis method is substantially equivalent to the difference method. However, according to the Fourier analysis method, not only the in-phase component but also the orthogonal component can be simultaneously detected as required.

[0018]

[Effects of the Invention] As explained above, according to the present invention,
It is possible to monitor and confirm that the powerful sound waves are converged on the treatment target area, and to reliably aim the focused high-power sound waves, thereby increasing the safety of the convergent high-power sound wave treatment.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the configuration of an apparatus according to an embodiment of the present invention.

FIG. 2 is a side view of a convergent high-intensity sound wave transmitter incorporating an ultrasonic pulse transducer used in the embodiment of FIG.
a) and bottom view (b).

[Explanation of symbols]

1-1, 1-2,..., 1-N... Convergent strong sound wave transmitter transducer element, 2-1, 2-2,..., 2-N... Ultrasonic pulse transducer transducer element, 5... Light metal spherical shell, 6... Acoustic matching layer, 7... Back damping layer, 10... Main control circuit, 11... Strong sonic wave transmitting circuit, 12... Ultrasonic pulse transmitting control circuit, 13... Wave transmitting/receiving circuit, 14... Receiving wave focus circuit, 15... difference circuit, 16... display circuit, 20... echo signal storage circuit.

Claims (3)

[Claims] 1. A medical ultrasonic device comprising a powerful sonic wave transmitter having a focus mechanism and a means for modulating the transmitted wave output, and an ultrasonic pulse transducer having directivity capable of scanning, the above-mentioned An apparatus characterized by having a mechanism for extracting a component of an output modulation frequency of the transducer from a received signal of the transducer. 2. The apparatus according to claim 1, wherein the output modulating means of the transmitter is means for intermittent or increasing/decreasing the transmitted wave output. 3. The apparatus according to claim 1, wherein the output modulation means of the transmitter is means for cyclically changing the transmission focal point.