JPH0710263B2 - Ultrasonic therapy equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an ultrasonic treatment apparatus for intensively irradiating an affected area with an ultrasonic shock wave to destroy and treat an affected area such as a kidney stone. Regarding

[Conventional technology]

A calculus breaking device as an example of an ultrasonic therapy device is known in, for example, Japanese Patent Application Laid-Open No. 60-145131.

FIG. 9 is a sectional view showing a schematic configuration of a wave transmitter in the above apparatus. As shown in the figure, this transmitter has a large number of piezoelectric elements 1.
By arranging in a mosaic shape to form a spherical surface,
A shock wave generator 2 is formed, and the shock wave generator 2 is brought into contact with a living body 4 via a liquid-filled bag 3 filled with a medium such as water, and a diseased part existing in the kidney 5, that is, a stone to be treated. 6, the ultrasonic shock waves from the large number of piezoelectric elements 1 are concentrated to destroy the calculus 6.

The ultrasonic shock wave is generated by applying a pulsed voltage from a shock wave generating circuit (not shown) to the piezoelectric element 1. A mechanical scan type ultrasonic probe 7 is attached to the central portion of the shock wave generator 2 in order to find and confirm the position of the calculus 6, and the ultrasonic wave observation device (not shown) is attached to the probe 7. Are connected.

[Problems to be Solved by the Invention] As the piezoelectric element 1 in the device shown in FIG. 9, a ceramic vibrator such as PZT (lead zirconate titanate) is usually used in consideration of conversion efficiency. Is used. However, since a ceramic vibrator generally has a high Q, for example, even if it is driven by a pulse, the sound pressure waveform of the ultrasonic wave generated is
As shown in FIG. 10, the waveform W has a long duration that oscillates around the sound pressure level of zero. When a signal having such an oscillating waveform is converged into the living body as described above,
When the negative sound pressure is large, cavitation may occur in the living body and destroy normal living tissue. Also, the degree of convergence is worse than that of the normal pulse.

Therefore, in the conventional device, a damping material is attached to the back surface of the ceramic vibrator to make the Q of the vibrator extremely small to achieve a wide band, and thus, FIG. 11 (a) (b).
As shown in FIG. 7, the device is devised so as to produce a vibration waveform of FIG. 9B which is substantially similar to the drive pulse waveform of FIG. 9A and has a small negative sound pressure. As another countermeasure example, the impedance characteristic 8 of the vibrator as shown in FIG. 12 has a flat portion (wideband portion) 9 below the resonance frequency fc.
There is also one that realizes a vibration waveform close to an ideal waveform by performing pulse drive using.

However, of the above two examples, in the former case, the band is widened by bonding damping materials,
There is a problem that the conversion efficiency becomes very poor. Further, in the latter case, since a region where the oscillator impedance is high and Q is small is used, there is a problem that the conversion efficiency is low as in the former case.

Therefore, the present invention can generate an ultrasonic shock wave of a vibration waveform having a low negative sound pressure and a high degree of convergence, and can perform highly safe and accurate treatment on a living body, and also has high conversion efficiency and power consumption. It is an object of the present invention to provide an ultrasonic therapy device that requires less.

[Means for solving problems]

The present invention takes the following means in order to solve the above problems and achieve the object. That is, each resonance frequency of a plurality of transducers arranged so as to form an ultrasonic wave transmitter is made to differ for each transducer according to the distance from the central axis of the ultrasonic wave transmitter, and within a certain frequency range. It was arranged to be distributed.

[Action]

By taking such a measure, it is possible to generate a vibration waveform with a small negative sound pressure while setting the Q of the vibrator to be high and keeping the conversion efficiency high. As a result, cavitation in the living body is less likely to occur, and safety to the living body can be enhanced. In addition, the degree of convergence at the convergence point is increased, the affected area can be treated appropriately, and the influence on the area other than the treated area is reduced, so that the safety can be further enhanced.

〔Example〕

FIG. 1 shows an embodiment of the present invention and is a front view of an ultrasonic wave transmitter 10. As shown in the figure, this ultrasonic wave transmitter 10 has a plurality of ring-shaped transducers 11, 12-arranged in a spherical shape. As shown in FIG. 2, the resonance frequency fc of each of the above-mentioned transducers is set to the number of transducers arranged (arrangement area) as the distance 1 increases from the center of the ultrasonic wave transmitter 10 toward the outside. Correspondingly distributed so as to increase gradually.
When the wave transmitter 10 having such a configuration is excited by a pulse and the ultrasonic shock wave is converged in the living body, the sound pressure distribution at the convergence point is as follows.

FIG. 3 is a schematic diagram of an apparatus shown for considering the sound pressure distribution at the convergence point of ultrasonic shock waves. For simplification of explanation, it is assumed in FIG. 3 that the transducers 11 and 12 are arranged one-dimensionally. Reference numeral 13 in the drawing is a pulse generator, and 14 is a delay line for fine adjustment so that the phases of the generated ultrasonic waves match at the convergence point.

Now, as shown in FIG. 4, the spatial frequency component fA in the direction of the central axis 15 of the transmitter 10, that is, the central axis of the ultrasonic pulse generated from the oscillators 11 and 12 is two in a linear step shape. If distributed, the sound pressure distribution P (x) in the direction of the central axis 15 at the convergence point is Indicated by. Note that fL represents the lowest frequency among the step frequencies, and Δf represents the frequency step width.

According to the above formula, the sound pressure distribution at the convergence point is as shown in FIG. That is, the negative sound pressure is small, the pulse width is relatively small, and the degree of convergence is high.

Next, the sound pressure distribution in the direction perpendicular to the central axis 15, that is, in the azimuth direction will be considered. The spatial frequency component fB in the azimuth direction of the ultrasonic pulse generated from the oscillators 11 and 12 is
It is approximately represented by a linear stepped frequency as shown in FIG. As shown in FIG. 6, the spatial frequency component f _{0 in} the azimuth direction of the oscillator at the center of the transmitter 10 becomes zero. In other words, the sound pressure distribution in the azimuth direction at the convergence point is fL =
It is the one with 0 substituted. This is shown in FIG. 7 as a diagram. That is, the negative sound pressure is still small and the pulse width is also narrow.

When the resonance frequencies of the transducers 11 and 12 are distributed, the negative sound pressure of the ultrasonic vibration waveform can be further reduced by weighting the amplitude of the excitation pulse and the number of transducers arranged. You can For example, if the amplitude of the low frequency component is increased as shown in FIG.
As described above, the pulse width is wide, but a vibration waveform in which the negative sound pressure is further suppressed can be obtained.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the gist of the present invention.

〔The invention's effect〕

 The present invention has the following effects.

Since the vibration waveform of the ultrasonic shock wave at the convergence point has a small negative sound pressure, cavitation does not occur in the living body, and the safety to the living body is improved.

Since the vibration waveform of the ultrasonic shock wave at the convergence point has a narrow pulse width, the degree of convergence of the ultrasonic shock wave to the treatment part is high, and accurate treatment can be performed, and it is safe for other living tissues. Will increase.

Since a high Q oscillator can be used, the conversion efficiency is good, the power consumption is low, and the device is simple.

[Brief description of drawings]

1 to 8 (a) and (b) are views showing an embodiment of the present invention. FIG. 1 is a front view of an ultrasonic wave transmitter, and FIG. 2 is a dispersion of resonance frequencies of respective transducers. Fig. 3 is a diagram showing the arrangement state, Fig. 3 is a schematic diagram of the device shown for considering the sound pressure distribution at the converging point of the ultrasonic shock wave, and Fig. 4 is a distribution state of spatial frequency components in the central axis direction of the ultrasonic pulse. FIG. 5, FIG. 5 is a diagram showing a sound pressure distribution at a convergence point corresponding to FIG. 4, and FIG. 6 is a diagram showing a distribution state of spatial frequency components in an azimuth direction perpendicular to the central axis of the ultrasonic pulse. , FIG. 7 is a diagram showing a sound pressure distribution at a convergence point corresponding to FIG. 6, and FIGS. 8 (a) and 8 (b) are diagrams showing ultrasonic vibration waveforms when the amplitude of a low frequency band is largely modulated. Is. 9 to 12 are views showing a conventional technique.
The figure is a cross-sectional view of an ultrasonic wave transmitter, and FIGS. 10 to 12 are views for explaining the drawbacks of the prior art. 10 …… Ultrasonic wave transmitter, 11,12 ～ …… Multiple ring transducers, 13 …… Pulse generator, 14 …… Delay line, 15 …… Central axis of wave transmitter, fc …… Resonance frequency , FA …… Spatial frequency component in the central axis direction, fB …… Spatial frequency component in the azimuth direction, fL ……
Lowest frequency, l ... Distance from the center of the transmitter.

Claims (1)

[Claims] 1. Resonant frequencies of a plurality of transducers arranged to form an ultrasonic wave transmitter are made different for each transducer according to a distance from a central axis of the ultrasonic wave transmitter, An ultrasonic therapy device characterized by being distributed and arranged in a certain frequency range.