JPS62155000A - Ultrasonic wave probe - Google Patents

Abstract

PURPOSE:To form a probe structure for large power irradiation by providing a mechanism which cools a piezoelectric vibrator and an acoustic matching layer. CONSTITUTION:The ultrasonic vibrator 1 made of piezoelectric ceramics such as PZT-based ceramics and lead titanate ceramics is adhered to the 1st acoustic matching layer 2 made of metal which is smaller in acoustic impedance than piezoelectric ceramics represented by light metal such as aluminum. The 2nd acoustic matching layer 4 made of acrylic resin,etc., is adhered to the acoustic matching layer 2 and an ultrasonic wave generated by the vibrator 1 passes through the 1st and the 2nd acoustic matching layers and a water bag 3 and then enters an object of irradiation, such as a living body, which has acoustic impedance close to that of water. Thus, a >=50% specific band width is obtained because of the presence of those two layers. The acoustic matching layer 2 of light metal is cooled with the circulating water in the water bag 3.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to an ultrasonic therapy device and an ultrasonic heating device.

This invention relates to probes for ultrasonic irradiation bags such as ultrasonic chemical reaction accelerators and ultrasonic crushing devices, and particularly to ultrasonic probes suitable as transmitters for devices with large irradiation power.

[Background of the invention]

Hyperthermia in cancer therapy (1!yperth
ermta In Cancer Therapy
y) Structures as described on pages 344-345 are known. This probe has a mechanical Q value as an electrical/acoustic transducer.

Since both use a crystal resonator with a high electrical Q value,
Even during high-power irradiation, the vibrator itself generates only a small amount of heat, and no special mechanism for cooling the vibrator is required.

However, the electrical/acoustic conversion efficiency is about 10 times higher than that of crystal, and the mechanical Q value is not very large when using low-cost piezoelectric ceramics as electrical/acoustic transducers. Therefore, heat generation of the vibrator itself during high power irradiation becomes a problem.

Furthermore, as shown in the example below, in actual applications, the irradiation probe is often required to have a certain wide band (mechanical Q value that is not too high); , it is necessary to provide an acoustic matching layer between the ultrasonic transducer and the irradiation medium.

(1) To prevent the occurrence of unintended irradiation areas due to standing waves,
Not only ultrasonic waves of one frequency, but also ultrasonic waves of multiple frequencies, frequency swept ultrasonic waves, and amplitude modulated ultrasonic waves are irradiated.

(2) Electronically scan the target irradiation area at high speed using an array probe. At this time, focusing on one element, even when irradiating with ultrasonic waves for 11 rounds, the drive signal needs to be phase modulated. Furthermore, the mechanical bandwidth of the probe structure must be at least as large as the variation in the center frequency of the element.

<3> The FL irradiation area is located by imaging using the echo method. At this time, since the irradiation of the irradiation ultrasound is temporarily suspended during the transmission and reception of the imaging ultrasound, the drive signal thereof is amplitude-modulated. Furthermore, if the irradiation probe has a broadband structure, it can also be used as an imaging probe.

The requirements shown in (1), (2), and (3) below cannot be met by an irradiation ultrasonic probe with a conventional structure.

[Purpose of the invention]

The purpose of the present invention is to solve the problem of heat generated by the vibrator itself during high power irradiation, thereby making it possible to use low-cost piezoelectric ceramics with a large electrical-mechanical coupling coefficient as an electrical-acoustic transducer. Another object of the present invention is to provide an ultrasonic probe structure for high power irradiation that does not have a narrow band.

[Summary of the invention]

In accordance with this objective, the present invention proposes a structure that includes a mechanism for cooling the piezoelectric vibrator and an acoustic matching layer in an ultrasonic probe that uses a piezoelectric vibrator as an electric/acoustic transducer. Furthermore, as one method for realizing this in an integrated manner, we propose using a light metal plate with high thermal conductivity as the acoustic matching layer in contact with the piezoelectric vibrator, and providing a structure in which the cooling medium is in contact with the light metal plate.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to Examples. FIG. 1(a), (+, )) is an ultrasonic wave for high-power irradiation, which is an embodiment of the present invention! ``'' They are an external view and a sectional view of the A-toucher.

PZT ceramics and ditanic acid buttons! Ultrasonic 1141 element made of piezoelectric ceramics such as Iramix! is bonded to the first acoustic matching layer 2 made of a metal having a smaller acoustic impedance than piezoelectric ceramics, typically a light metal such as aluminum. In the illustrated embodiment, the sound I
! The thickness of the I matching layer 2 is 1/4 wavelength, but generally 1
-//It is sufficient if it is an odd number multiple of I wavelength. Also, the sound! J
! The matching layer 2 is made of acrylic resin (PMMA) or the like. The I matching layer 4 is bonded, and the vibrator 1
The super r'-f waves generated pass through the first and second sound W matching layers, enter the water bag 3, and enter an irradiation target having an acoustic impedance close to that of water, such as a cow's body. These two matching layers realize a fractional bandwidth of 50%1 or more. 1st
In the example shown in the figure, the light metal acoustic tfIJ matching layer 2 has a structure in which it is cooled by the circulating water of the water bag 3, while in the example shown in FIG. 2, the light metal acoustic matching layer 2 is provided with cooling piping 5. It has a structure in which it is cooled by a cooling medium circulating therein.

With this structure, the heat generated in the ultrasonic transducer 1 is absorbed by the cooling medium through the light metal acoustic matching layer, and as a result, damage and performance deterioration due to heating of the transducer 1 during high power irradiation are prevented. Ru.

In addition, since the matching layer allows the probe to have a wide band, it can handle not only the center frequency of the piezoelectric vibrator, but also ultrasonic waves at a frequency several percent off the center frequency, frequency-swept ultrasonic waves, and amplitude-modulated ultrasonic waves. It is possible to irradiate ultrasonic waves. The position of the non-target irradiation area due to the standing wave is located at the antinode of the standing wave caused by the interference of sound waves from a plurality of sound sources and reflectors, and therefore moves depending on the frequency. Hence, multiple frequency irradiation.

If ultrasonic irradiation is performed using techniques such as frequency sweep and amplitude modulation, it will be possible to prevent the time-averaged Tf wave power from concentrating on the unintended irradiation area, and as a result, it will be possible to prevent the unintended irradiation area from becoming problematic. This can be prevented from occurring.

2(a) and 2(b) are (l/, top view, and partial cross-sectional view of another embodiment of the present invention. The same reference numerals as in FIG. - Figures (n) (+)) show parts corresponding to the parts described in (+)).

The embodiments shown in Fig. 1 and Fig. 2 are both examples of array type probes, but even when using this to electronically scan the focal range at high speed, the wide 'Ill' area of the probe ization is helpful. That is, even when performing irradiation with a single frequency, when focusing on one element, its drive signal is phase-modulated in accordance with electronic scanning. The degree of phase modulation increases in proportion to the scanning speed. Also, what is the center frequency of the elements forming the array? Although it may vary by a few percent depending on the manufacturing process, if the ratio A/F range width of the probe is larger than this, there will be no problem when operating the array type probe.

Both embodiments also include an imaging probe 8 for illumination monitoring.
and its mechanical scanning mechanism 9. This imaging probe is
This is necessary for positioning the target irradiation area using ultrasound and for monitoring during irradiation.

When the imaging ultrasound frequency and the irradiation ultrasound frequency are close to each other, the irradiation of the irradiation ultrasound must be stopped while the imaging ultrasound is being transmitted and received. The irradiation ultrasonic waves will be irradiated intermittently, or in other words, the amplitude will be modulated. Therefore, from this point of view as well, it is effective to widen the band of the irradiation probe. Furthermore, although an ultrasonic transducer exclusively used for imaging is used here, it is also possible to use the irradiation probe also as an imaging probe by utilizing its broadband characteristics.

In the embodiments shown in FIGS. 2(a) and 2(b), the light metal matching layer 5 is intended to simultaneously serve as an acoustic Fresnel lens for directing the element directivity of the ultrasonic transducer 1 inward. In addition, the thickness of the light metal plate is changed from the outside to the inside of the element in a washboard shape around 1/4 wavelength.

FIG. 3 shows a block diagram of an embodiment of an ultrasound irradiation system constituted by the ultrasound probes of these embodiments.

The focal position, focal scanning method 4 frequency sweep width, and amplitude modulation method are determined according to the position and size of the target irradiation area and the position of strong reflectors existing in the vicinity, and the main control circuit 10
is applied to the drive signal calculation circuit 11, where the waveform 1. of each element for one cycle of scanning and sweeping is generally expressed by the following equation. /k(t) is calculated and written to the waveform memory]2 of each element.

Vh(t + τk(t))=Ah(t)sin(2x
f (t) t)...(1) Here, k is the element number, Ah(t) is the drive amplitude for each element, fD) is the drive frequency, and τk(t) is the drive delay time for each element. be. The position of the scanned focus is τk(1) and A,b(t
) is determined by The waveform recorded in the memory 12 is read out with the period between the elements determined by a clock from the main control circuit O, and is amplified by the transmission amplifier 13 to drive the irradiation probe element J.

Next, the imaging block will be explained.

In FIG. 3, each element of the probe 8 is connected to a wave transmission control circuit ]-6 and a reception focus circuit 17 via a wave transmission/reception amplifier J-5. The obtained echo tomographic image 20 is displayed on the display 19 by the display circuit 18 while being superimposed on the intersection line 22 of the irradiation region mark 2 and the plurality of tomographic planes.

〔Effect of the invention〕

As explained above, according to the present invention, a low-cost piezoelectric material with a large electrical-mechanical coupling coefficient can be used as an electrical-acoustic transducer, and various treatments for irradiating a target irradiation area in a limited manner can be used. It becomes possible to realize a broadband reduced-power ultrasonic probe that enables implementation of the following. Therefore, the effects of the present invention in various industrial fields and medical care are extremely large.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are both an external view and a cross-sectional view of a broadband ultrasonic probe for high power irradiation, which is an embodiment of the present invention. FIG. 3 is a block diagram of an embodiment of an ultrasound irradiation system using the probe of the present invention. 1... Ultrasonic transducer, 2... Light metal foil 1-acoustic matching layer. 3... Water bag, 4... Second sound W matching layer, 5... Cooling piping, 6... Cooling medium inlet, 7... Cooling medium outlet, 8... Ultrasonic probe for imaging, 9... Ultrasonic probe for imaging mechanical scanning mechanism, 10... Main control circuit,
11... Drive signal calculation circuit, 12... Waveform memory,
13... Transmission amplifier, 15... Transmission/reception amplifier, 16
... Transmission control circuit, ]-7 ... Reception focus circuit, 18 ... Display circuit, 19 ... Display device, 20 ...
Echo tomographic image, 21... Irradiation area mark, 22...
Intersection line of multiple fault planes.

Claims (1)

[Claims] 1. An ultrasonic probe using a piezoelectric vibrator as an electric/acoustic transducer, characterized by comprising a mechanism for cooling the piezoelectric vibrator and an acoustic matching layer. probe. 2. The ultrasonic probe according to claim 1, wherein the acoustic matching layer is made of a metal having a smaller acoustic impedance than the piezoelectric vibrator, and the acoustic matching layer has a structure in which a cooling medium is in contact with the acoustic matching layer. An ultrasonic probe comprising: 3. In the ultrasonic probe according to claim 1, the front IC acoustic matching layer is made up of a plurality of layers, the piezoelectric vibrator is made of a piezoelectric ceramic vibrator, and among the plurality of layers, the piezoelectric An ultrasonic probe characterized in that a first layer in contact with a ceramic vibrator is made of metal.