JPWO2005094701A1 - Ultrasonic irradiation method and ultrasonic irradiation apparatus - Google Patents

Abstract

The information obtained from the behavior of the generated cavitation bubbles is used to optimize the ultrasonic irradiation. A first step of irradiating an object having liquid in at least a part of its surroundings with a high-frequency ultrasonic wave to generate cavitation bubbles in a region including the object, and a low-frequency ultrasonic wave to the object A first step comprising: a second step of irradiating the cavitation bubble to collapse the cavitation bubbles and imparting high energy to the object; and a third step that is an interval time after the second step; A second step of acquiring a sound wave emitted from the cavitation bubble and controlling the ultrasonic wave irradiation condition by signal processing the sound wave. The second step includes determining whether a stable cloud cavitation has been generated, whether the collapse position is appropriate, whether the collapse pressure is appropriate, and whether there are few remaining bubbles.

Description

The present invention relates to an ultrasonic irradiation method and an ultrasonic irradiation device, and more particularly to crushing, cleaning, surface modification, etc. of an object using the collapse pressure of cavitation bubbles. In this specification, although this invention is demonstrated based on the calculus crushing which is one preferable aspect, this invention is not only in medical applications, such as calculus crushing, but in industrial applications, such as ultrasonic cleaning and cavitation peening. Is also useful.

Shock wave lithotripsy (SWL) is often regarded as an almost established treatment technique at present. However, it is also true that calculus fragments are relatively large and have unresolved problems that normal tissue is damaged by cavitation. The damage to the body tissue is caused by a large impact pressure generated when the cavitation bubble collapses (collapses) rapidly. On the other hand, the collapse pressure of the cavitation bubble is certainly sufficient to scrape off the stone. If it can localize only on the surface of the stone and generate cavitation bubbles, and if it can effectively cause the collapse, then only the stone will be crushed while minimizing damage to normal tissue It is considered possible.

The inventors of the present application have developed a technique for controlling ultrasonic cavitation with two kinds of focused ultrasonic waves and crushing only stones from the surface. In this method, only stones are crushed by erosion due to the collapse phenomenon of ultrasonic cavitation without using high pressure due to shock waves. As the pressure wave that generates cavitation, compared to the shock wave generated by SWL, focused ultrasound with a wavelength that is one order of magnitude shorter is used. By generating cavitation in a localized region and causing collapse, only the calculus surface Guides the concentration of high pressure and energy. As a result, we developed a stone crushing technique that can solve both the relatively large fragments and the damage of body tissue due to cavitation damage, which are problems of existing SWL.

Until now, in the method using two kinds of ultrasonic waves, sequential control has been performed by giving an ultrasonic output and an ultrasonic irradiation time which are considered to be appropriate empirically. For example, the time required for cavitation generation is 50 μs, and the time required for annihilation is 50 ms. However, in the present method of generating stable cavitation with high-frequency ultrasound and then breaking it down with subsequent low-frequency ultrasound to obtain very high pressure in a very limited space-time domain, It is important to keep track of the status of the system and to maintain the optimal status at all times. In particular, when considering medical applications, it is important to 1) not to apply cavitation collapse pressure to other than the affected area, and 2) to maximize (optimally) the collapse of cavitation in the affected area.

Here, as a result of researches by the inventors, the crushing force largely depends on the accuracy of the generation of stable cloud cavitation, and the generation of stable cloud cavitation depends on the pressure amplitude at the focus, dissolved gas concentration, bubble core concentration, saturation. It was found that the optimum ultrasonic irradiation conditions in the system greatly vary depending on the vapor pressure and so on. Here, as shown in FIG. 8, the stable cloud cavitation indicates a state in which the change rate of the size and shape of the cloud cavitation is remarkably reduced when a certain ultrasonic irradiation time is exceeded. In addition, the amount of crushing per unit time greatly depends on the number of stable cloud cavitation disruptions per unit time, that is, the repetition frequency of high-frequency ultrasound and low-frequency ultrasound, and the repetition frequency remains after the collapse of cloud cavitation. It depends greatly on the disappearance time of bubbles. In order to use two types of ultrasonic techniques in more advanced ultrasonic therapy equipment, we can physically grasp a series of behaviors from the generation, collapse, and disappearance of acoustic cavitation in a focused ultrasonic field. However, it is necessary to control the concentration of high pressure and high energy.
JP 2004-33476 A

The present invention provides a cavitation bubble generated in a means for generating cavitation by high-frequency ultrasound, collapsing it with subsequent low-frequency ultrasound, and generating very high energy in a limited space-time region. The objective is to optimize the ultrasonic irradiation using information obtained from the behavior of the above. Energy concentration efficiency greatly depends on the accuracy of stable cloud cavitation generation, and stable cloud cavitation generation largely depends on pressure amplitude at the focal point, dissolved gas concentration, bubble nucleus concentration, saturated vapor pressure, etc. The optimum ultrasonic irradiation method in the system greatly varies depending on these. The total amount of energy concentrated per unit time depends greatly on the number of stable cloud cavitation decays per unit time, that is, the repetition frequency of high frequency ultrasound and low frequency ultrasound, and the repetition frequency is collapsed by cloud cavitation. It largely depends on the disappearance time of the remaining bubbles later. Therefore, it is necessary to control the energy concentration while constantly grasping a series of behaviors from the generation of cavitation due to ultrasonic waves to the collapse and disappearance.

The technical means adopted by the present invention in order to achieve such a problem is that high-frequency ultrasonic waves are radiated toward an object in which liquid is present in at least a part of the periphery, and cavitation bubbles are formed in a region including the object. A first step of generating, a second step of irradiating the object with a low-frequency ultrasonic wave to collapse the cavitation bubble and imparting high energy to the object; and a step after the second step A first step having a third step which is an interval time (interval step); a second step of acquiring ultrasonic waves emitted from the cavitation bubbles and controlling ultrasonic irradiation conditions by performing signal processing on the sound waves And having. Preferably, the cavitation bubbles are generated in a local region in the vicinity of the object, and high energy is locally given to the object by collapsing the cavitation bubbles. In a preferred embodiment, the third step of the first step is an interval in which, after the second step, only an ultrasonic wave having an intensity that does not irradiate ultrasonic waves toward the object or does not induce generation and growth of bubbles is irradiated. It's time.

In one preferred embodiment, the signal processing in the second step includes determining whether stable cavitation bubbles have been generated by the first step in the first step, and the controlled ultrasonic irradiation condition is a high frequency ultrasonic wave. Output and / or irradiation time. When the determination result is “No”, the output and / or irradiation time of the high frequency ultrasonic wave is reset. The controlled ultrasonic irradiation conditions may include a high frequency ultrasonic frequency. The ultrasonic irradiation conditions to be controlled may further include position adjustment (including phase) of the ultrasonic irradiation apparatus.

In one preferred embodiment, whether or not a stable cavitation bubble has been generated is determined by using the pressure amplitude and / or the pressure level of the received signal. In another preferred embodiment, whether or not a stable cavitation bubble has been generated is determined by using the frequency component of the received signal.

In one preferable aspect of the present invention, the signal processing in the second step includes determining whether or not the collapse position of the cavitation bubble in the first step and the second step is appropriate, and the controlled ultrasonic irradiation condition is the positioning (Including phase). If the determination result is “No”, the position of the apparatus is adjusted. Whether or not the collapse position of the cavitation bubble is appropriate is determined by measuring the time from the transmission of the low frequency ultrasonic wave to the reception of the sound wave by the collapse pressure.

In one preferable aspect of the present invention, the signal processing in the second step includes determination of whether the collapse pressure of the cavitation bubbles in the second step of the first step is appropriate (determination of whether the crushing efficiency is appropriate). The ultrasonic irradiation conditions to be controlled include at least one of an output of a low frequency ultrasonic wave, a wave number, a rising time constant, a rising phase, and a frequency. Furthermore, the ultrasonic irradiation conditions to be controlled may include at least one of high-frequency ultrasonic parameters (output, irradiation time, frequency), positioning, and phase correction. In one preferred embodiment, whether the collapse pressure of the cavitation bubble is appropriate is determined by measuring the pressure amplitude and / or the magnitude of the pressure of the sound wave reception signal based on the collapse pressure.

In one preferable aspect of the present invention, the signal processing in the second step includes a determination as to whether or not the residual bubbles in the first step and the third step are sufficiently small, and the controlled ultrasonic irradiation condition is a repetition frequency. is there. In a preferred embodiment, this determination is made based on the collapse pressure and / or collapse time of the residual bubbles.

In the present invention, processing of sound waves generated from the cavitation bubbles may include obtaining an image of the cavitation bubbles based on the sound waves. Furthermore, the method may include the step of acquiring and signal processing a sound wave from the object and / or the environment surrounding the object. The signal processing may include obtaining an image of the object and / or the surroundings of the object using a sound wave signal from the object and / or an environment around the object.

In the present invention, the second step of the first step includes, in some preferred embodiments, crushing of the object, separation of foreign matter from the object, surface modification of the object, and thermal modification of the object.

The present invention is also provided as an ultrasonic irradiation apparatus. An ultrasonic irradiation apparatus according to the present invention includes an ultrasonic irradiation unit that irradiates an object with ultrasonic waves based on set ultrasonic irradiation conditions, a sound wave reception unit, and a signal that processes a signal received by the sound wave reception unit A processing unit, and a control unit that controls ultrasonic irradiation conditions of the ultrasonic irradiation unit, and the ultrasonic irradiation unit causes high frequency ultrasonic waves to be present in at least a part of the periphery by the control unit. Irradiating the target object, generating cavitation bubbles in a region including the target object, and then irradiating the target object with low-frequency ultrasonic waves to collapse the cavitation bubble, The sound wave receiving unit receives the sound wave emitted from the cavitation bubble and processes the received sound wave by the signal processing unit, so that it is based on the signal processing result. To the control unit What it is configured to control the ultrasound irradiation condition.

In a preferred embodiment, the sound wave receiving unit is an ultrasonic probe and / or a hydrophone.

In one preferred embodiment, the signal processing unit includes a sound pressure analysis unit for the received sound wave. The sound pressure analyzer can analyze pressure amplitude, pressure magnitude, collapse position, collapse time, collapse pressure, and the like.

In another preferred embodiment, the signal processing unit includes a frequency analysis unit for received sound waves. The frequency analyzer can analyze pressure amplitude, pressure magnitude, collapse pressure, and the like.

In one preferred embodiment, the apparatus further comprises means for irradiating the ultrasonic wave with an intensity that does not induce bubble generation and growth, from the object and / or the environment surrounding the object and / or cavitation bubbles. The reflected sound wave of the ultrasonic wave is processed by the sound wave receiving unit.

In one preferable aspect, the signal processing unit includes an image processing unit that obtains image information based on the received sound wave.

In a preferable example, the ultrasonic irradiation conditions are not limited. The output of the high frequency ultrasonic wave, the irradiation time of the high frequency ultrasonic wave, the frequency of the high frequency ultrasonic wave, the positioning of the ultrasonic irradiation unit with respect to the object, the repetition frequency, the low frequency It includes one or more selected from the group consisting of sound wave output, wave number, rise time constant, rise phase, and frequency.

In another preferable aspect, the apparatus includes a storage unit, and information indicating a relationship between the ultrasonic irradiation condition and the physical condition is stored in the storage unit.

According to the present invention, using information obtained from the behavior of the generated cavitation bubbles, whether stable cloud cavitation is generated, whether the collapse position is appropriate, whether the collapse pressure is appropriate, It is possible to determine whether there are enough bubbles, etc., and based on the determination result, reliably generate stable cloud cavitation, and lead to stable cloud cavitation to collapse at a reliable and accurate time and position. The ultrasonic irradiation conditions can be reset to the repetition frequency.

[A] Ultrasonic irradiation method using two types of frequencies First, ultrasonic irradiation using two types of frequencies according to the present invention will be described. First, the basic configuration of the calculus breaking device will be described. FIG. 1 shows a schematic diagram of an ultrasonic cavitation experiment apparatus according to the present invention. A concave PZT (lead zirconate titanate) transducer with an aperture diameter of 80 mm and a focal length of 80 mm fixed to an acrylic water tank was used as a source of focused ultrasound. Two types of PZT elements with resonance frequencies of 1.08 MHz and 545 kHz were used. As a characteristic of the PZT element, in addition to the resonance frequency of the fundamental mode, there are (2n + 1) times higher-order mode resonance points, and higher output is possible compared to other frequencies.

The waveform of the ultrasonic wave transmitted from the PZT transducer into the acrylic water tank is created on a PC, then generated by an arbitrary waveform generator (Agilent, 33120A), and amplified by an ultrasonic band amplifier (T & C Power Conversion, AG1024) And sent to the PZT element. The transmitted ultrasonic wave is focused at a position of 80 mm, which is the geometric focus of the concave PZT element. The maximum output of AG1024 is 2 kW for continuous sine wave transmission and 800 V for voltage amplitude during pulse transmission.

For observation of the cavitation phenomenon, DRS Hadland's frame mode ultra high-speed camera IMACON 200 was used. The IMACON 200 can capture images with a minimum exposure time of 5 ns and an inter frame of 5 ns, and has sufficient performance to capture the cavitation phenomenon generated by ultrasonic waves on the order of MHz. In addition, a high-speed camera has a long-range microscope (Quester, QM100, focal length 150 to 350
mm), a region of 0.33 mm × 0.40 mm to 2.50 mm × 3.06 m was photographed on a CCD image of 1200 pix × 980 pix. Daylighting in the cavitation generation range was performed using a high-intensity strobe point light source (Nisshin Electronics, SA200F) with a maximum light intensity of 200 J / flash. The light from the point light source was converted into parallel light by the lens system and then guided to the test section, where the phenomenon of ultrasonic cavitation was observed and the shadow wave of the collapsed wave was photographed. Sound pressure due to cavitation decay was measured with a hydrophone for shock wave measurement (IMOTEC, Type 80-0.5-4.0, rise time 50 ns). In addition, synchronized data of sound pressure measurement and phenomenon shooting by a high-speed camera was performed with reference to a trigger signal from an arbitrary waveform generator. An aluminum sphere was used as the solid wall surface for growing cavitation. In addition, the experiment was performed in a state where the water in the water tank was continuously deaerated to 1.0 to 2.0 ppm in the dissolved oxygen concentration.

FIG. 2 shows a schematic diagram of a cavitation control method and an outline of an ultrasonic pulse waveform used for acoustic cavitation control. The acoustic cavitation is controlled by focused ultrasound with two different frequencies. One is a high-frequency (about 1 MHz to 4 MHz) ultrasonic wave that generates cavitation in a narrow region (FIGS. 2-1, 2). High-frequency ultrasonic waves generate cloud cavitation composed of a large number of microbubbles in the focal region. The other ultrasonic wave is a low-frequency ultrasonic wave (about 100 kHz to 1 MHz) having a frequency around the resonance frequency as a group of cloud bubbles, which is about one order lower than the high-frequency ultrasonic frequency. As shown in FIG. 5, the high frequency ultrasonic wave is applied immediately after it is stopped. This low frequency ultrasonic wave causes the cloud generated at a high frequency to vibrate and lead to collapse (Figs. 2-3, 4). The shock wave is focused inside the cloud placed in the oscillating pressure field, and the bubble collapses violently in the center (Figs. 2-5 and 6). As a result of this series of schemes, cloud cavitation is generated at a spatially controlled position, and by further inducing its collapse, efficient stone crushing can be realized.

Next, the collapse behavior of cloud cavitation will be described. Fig. 3 shows the behavior of cavitation when acoustic cavitation by focused ultrasound is actually generated and collapsed using the above method. Fig. 3 (a) shows how cloud cavitation produced by 2.75MHz high-frequency ultrasound is led to collapse by 545kHz low-frequency ultrasound.

The semi-elliptical spherical cloud cavitation as seen in the first frame of FIG. 3A can be generated while maintaining a stable size and shape as long as the frequency of the high frequency ultrasonic wave is the same. In addition, it is known that cloud cavitation generated at different frequencies strongly depends on the wavelength of the ultrasonic wave. By changing the frequency of the high frequency, cloud cavitation of any size is generated in the localized area of the calculus surface. can do. This will be supplemented. After irradiating ultrasonic waves continuously for 100 to 200 μs, the state of cloud cavitation developed on the wall surface was observed. FIG. 26A is a photograph of cloud cavitations of a semi-elliptical sphere shape, which is generated by focused ultrasound at various frequencies and has a stable size and shape. Stable semi-ellipsoidal cloud cavitation was formed in the focal region of the ultrasonic wave on the solid wall at all frequencies of 1.67, 2.75, 3.27, and 3.82 MHz. FIG. 26B is a plot of representative length versus frequency for cloud cavitation as shown in FIG. 26A. As the representative length, the maximum cloud length in the normal direction of the solid wall surface was used. From FIG. 26B, the length of the cloud cavitation generated on the solid wall surface by the ultrasonic wave has a strong correlation with the wavelength of the ultrasonic wave, and it fits very well to a line that is a quarter of the wavelength. The result that the bubble cloud size is uniquely determined by the wavelength is considered to be because the sound field generated by the standing wave near the solid wall has a large influence on the cloud generation region. As a result, FIGS. 26A and 26B show that cloud cavitation that develops on a solid wall surface by focused ultrasound can control the generation region by the wavelength of the ultrasound. In addition, it was found that ultrasonic waves of 1.0 MHz or more can be guided to a localized region of 1.0 mm or less.

In the 2nd and 3rd frames of Fig. 3 (a), the semi-elliptical spherical cloud cavitation collapses in the positive pressure part of the 545 kHz ultrasonic wave by reducing the volume of each bubble that makes up the cloud. The state can be confirmed. At this time, it is considered that a large number of bubbles collapse violently in the center of cloud cavitation and exert a very high pressure on the solid surface. That is, by disrupting cloud cavitation, high pressure can be spatially controlled and focused only on the calculus surface.

FIG. 3 (b) is a shadow graph image showing the state of shock wave propagation due to the collapse of cloud cavitation that occurs subsequent to FIG. 3 (a). Although the ultrasonic frequency is different, it corresponds to the phenomenon immediately after the collapse of cloud cavitation in the third frame of Fig. 3. The high frequency ultrasonic wave is 3.82 MHz, and the subsequent low frequency is 545 kHz. In FIG. 3 (b), it can be seen that the spherical wave centering on the bubble cloud propagates outward. In the shadow graph image, black and white shades appear where the gradient of density change is large. That is, the shadow of the shock wave seen in FIG. 3 (b) indicates that a very high pressure is generated at that location. Actually, when the impact pressure at this time was measured in the distance, a pressure value more than three times the impact pressure when each single cavitation bubble collapsed was observed.

Furthermore, the phenomenon of Fig. 3 (a), (b) is observed every time in almost the same frame of high-speed camera shooting, and even in the impact pressure sensor measured far away, the variation in the signal of cloud cavitation collapse is ± 100 nsec. From this, it was found that high pressure and high energy can be focused in a region that is very controlled in time.

A crushing experiment will be described. Here, we will describe the results of confirming the applicability of crushing model stones and kidney stones using the above method. Figures 4 (a) and 4 (b) show the results of applying this method to model stones. FIG. 4 (a) shows a model calculus for each ultrasonic irradiation time, and FIG. 4 (b) shows a crushed piece. The cavitation control waveform was the same as that shown in FIG. 2, and a group of high frequency and low frequency was taken as one pulse, and ultrasonic waves were irradiated at a repetition frequency of 25 Hz. In other words, cloud cavitation collapses 1500 times per minute on the stone surface.

From FIG. 4 (a), it can be seen that the calculus is crushed so as to be scraped off from the surface. After 12 minutes, the model calculus had been scraped off almost one third of its mass, and in 30-40 minutes the model calculus was completely crushed. This is as efficient as the total treatment time (60-120 minutes) with existing SWL devices. Further, from FIG. 4 (b), it can be seen that the crushed pieces are crushed so as to be scraped off by cavitation erosion. All fragments are less than 1 mm and are considered large enough to painlessly pass through the urethra.

Fig. 4 (c) shows the application of this method to a cystine calculus, which is the hardest kidney calculus and is difficult to crush with existing SWL devices. As in the case of the model calculus, it can be seen that the calculus has been cut into very fine fragments. According to this method, 1) stones are scraped off by cavitation erosion, and fragments can be made very fine. 2) Ultrasonic cavitation that causes crushing is localized only on the stone surface. Therefore, it has the potential to solve the two problems of existing SWL devices: calculus fragmentation is relatively large, and damage to normal tissues in the body during crushing. In addition, about the ultrasonic irradiation method using two types of frequencies, description of Unexamined-Japanese-Patent No. 2004-33476 can be referred suitably.

[B] System using feedback control [B-1] Background of feedback control In the ultrasonic irradiation method using the two types of frequencies described above, in order to induce the collapse of cavitation, Stable cloud cavitation must be generated accurately. As a result of intensive studies by the inventors, it was found that the crushing force greatly depends on the generation of stable cloud cavitation. In addition, the range in which stable cloud cavitation can be generated is limited. For example, in this experimental system shown in FIG. 1, as shown in FIGS. It has also been found that this depends on the ultrasonic irradiation condition of ultrasonic output. Here, the magnitude of the ultrasonic output has a strong correlation with the magnitude of the ultrasonic pressure amplitude at the focal point, but there are many cases where the influence of reflection, refraction, and scattering in the propagation process of the ultrasonic wave cannot be ignored. In addition, the relationship between the pressure amplitude at the focal point and the generation of stable cloud cavitation is highly dependent on the dissolved gas concentration at the focal point, the bubble core concentration at the focal point, the saturated vapor pressure at the focal point, and the atmospheric pressure at the focal point, The optimum ultrasonic irradiation conditions in the system vary greatly depending on these. Therefore, it is important to monitor the state of cavitation and provide feedback even for one of “to ensure the generation of stable cavitation”.

On the other hand, in the process of generating stable cloud cavitation, it was also found that the sound wave generated from cavitation changes characteristically. Therefore, it is possible to control to generate appropriate cloud cavitation under various conditions by applying feedback using sound waves generated from cavitation. Furthermore, since the sound wave generated from cavitation also has information on the collapse phenomenon and residual bubble vibration after the collapse, this is analyzed and feedback is applied to obtain the appropriate collapse pressure and the appropriate repetition frequency of ultrasonic irradiation. (This is directly linked to crushing efficiency).

In the present invention, as a specific monitoring method, a sound wave generated from cavitation can be used as one preferred embodiment. The sound generated from cavitation is shown in FIG. By processing this sound, it is possible to perform all of the focus position target, whether cavitation is generated, whether the crushing is sufficiently performed, and optimization of the ultrasonic repetition frequency. As shown in FIG. 7, when the cloud is stabilized, a signal corresponding to the irradiation time of the high frequency ultrasonic wave is changed. Therefore, it is determined whether stable cloud cavitation is generated by monitoring the change in the signal. When the cloud collapses, an impact pressure corresponding to the strength of the collapse is observed. The collapse pressure is estimated from the pressure amplitude and / or the magnitude of the received sound wave due to the impact pressure, and it can be determined whether or not the crushing efficiency is appropriate. In addition, in this technique, since it is crushed so as to be scraped off by an object (calculus) erosion, it is important to say how fast the object (calculus) is scraped off. Therefore, the crushing efficiency is an amount such as a weight (mg / min) scraped per unit time, for example. Residual bubbles collapse after 100-200 μs and generate sound waves. The optimum repetition frequency is determined from the pressure amplitude and / or the magnitude of the pressure of the sound wave reception signal and the collapse time.

[B-2] Overall Configuration of System The overall configuration of the system will be described. The calculus crushing method (CCL: Cavitation Control Lithotripsy) using the collapse pressure of cavitation is configured as shown in FIG. The system can be broadly divided into two types: stone capture and stone crushing. The capture of the calculus includes measurement of the position of the calculus, coarse / fine movement of the ultrasonic generator, and phase correction of the ultrasonic generator. The crushing of stones includes two steps of irradiation with high-frequency ultrasonic waves and irradiation with low-frequency ultrasonic waves. The crushing process of stones is related to the process from generation to disappearance of cavitation bubbles. Specifically, the generation of stable cloud cavitation, the collapse of cloud cavitation, and the disappearance of cloud cavitation are important.

High-frequency ultrasonic irradiation is related to the generation of stable cloud cavitation. By monitoring the cavitation generation state during or after high-frequency ultrasonic irradiation (including after low-frequency ultrasonic irradiation) Determine whether a stable cloud cavitation has been generated. Low-frequency ultrasonic irradiation is related to the collapse of cloud cavitation, and it is determined whether or not appropriate collapse has occurred by monitoring the collapse phenomenon during or after low-frequency ultrasonic irradiation. Further, by monitoring residual bubbles after irradiation with low-frequency ultrasonic waves, it is determined whether or not cavitation bubbles have disappeared (or are sufficiently small). Steps (1) to (2) in the flowchart shown in FIG. 6 correspond to a stone capturing block, and steps (3) to (8) correspond to a stone crushing block.

The ultrasonic irradiation apparatus according to the present invention has means for receiving a sound wave emitted from a cavitation bubble. In the experimental apparatus of FIG. 1, a hydrophone is used as a sound wave receiving means, but one preferred form of the receiving means is an ultrasonic probe. FIG. 12 illustrates three types of receiving means. The left figure in FIG. 12 shows an ultrasonic probe installed inside a piezoelectric element that emits high-frequency and / or low-frequency ultrasonic waves, and the central figure emits high-frequency and / or low-frequency ultrasonic waves. In the case where an ultrasonic probe is installed outside the piezoelectric element, the piezoelectric element that irradiates high-frequency and / or low-frequency ultrasonic waves, or the type in which the piezoelectric element is divided into a plurality of segments, as shown in the figure on the right Some of them are responsible for receiving functions. These forms receive sound waves alone or in combination. The reception can have both a function of monitoring cavitation bubbles and a function of normal ultrasonic diagnosis for imaging a stone and a tissue. Moreover, after having these receiving means, whether the form of the treatment apparatus is a phased array system (the focal position can be changed by phase correction) or a single focus system is changed. The sound pressure signal receiving probe may passively receive the sound wave emitted from the cavitation bubble, or the probe itself transmits an ultrasonic wave (a waveform generator is connected to the probe) You may receive the reflected wave from the cavitation bubble with respect to a sound wave.

The sound pressure signal received by the ultrasonic probe is subjected to signal processing in the signal processing unit. In the signal processing unit, means for obtaining the pressure amplitude and / or the magnitude of the pressure of the received sound pressure signal, and the sound pressure signal are analyzed (frequency component extraction by frequency filter, frequency analysis by Fourier transform such as FFT). Means for obtaining a frequency component and means for obtaining image information from a sound pressure signal. The pressure amplitude and / or pressure magnitude of the sound pressure signal and the frequency component of the sound pressure signal can be used as parameters in the feedback loop. Further, the image information acquired from the sound pressure signal is displayed on the display unit, and the image information can also be used for feedback control.

[B-3] Crushing Procedure Using Feedback System A series of crushing processes using the feedback system will be described based on a flowchart. In the storage unit of the device, the dependence of physical parameters on the ultrasonic parameters is stored as a database. Here, the ultrasonic parameter means a parameter including the focal position of the ultrasonic generator, specifically, the positions of the ultrasonic generator and the receiver (including those by phase correction), and the high frequency ultrasonic wave. The output, the irradiation time, the frequency, the output of the low frequency ultrasonic wave, the wave number, the rising time constant, the rising phase, the frequency, and the repetition frequency of the first step. Physical parameters include the state of the medium, dissolved gas concentration, liquid type, liquid temperature, bubble core concentration, saturated vapor pressure, atmospheric pressure, etc., as well as the acoustic impedance and surface roughness of the object. Is included.

Ultrasonic parameters are set based on the database and calculus position information (step 1). Information on the calculus position is obtained by, for example, ultrasonic diagnosis. In this step, for example, positioning is performed first, then parameters of high frequency and low frequency ultrasonic waves and a repetition frequency are provisionally set, and then only high frequency ultrasonic waves are actually irradiated continuously to perform cavitation. The high-frequency ultrasonic parameters are reset using the feedback method in step 5 described later, and the low-frequency ultrasonic waves and the repetition frequency are optimized in the loop of steps 2 to 8. A method can be considered.

In order to follow the movement of the calculus, the position of the calculus is measured again, and the apparatus is positioned (including that by phase correction) (step 2). At this time, if it is impossible to follow the movement of the calculus in real time, it is possible to return to step 1 again and reset the ultrasonic parameters from the beginning.

Irradiate high frequency ultrasonic waves to generate stable cloud cavitation (step 3). High-frequency ultrasonic irradiation is performed based on the parameters set in step 1. The high frequency range is 100 kHz or more, and preferably 500 kHz to 10 MHz.

Subsequently, low-frequency ultrasonic waves are irradiated, the cloud cavitation is led to collapse, and the stone is crushed (step 4). The low frequency range is less than or equal to half the frequency of the ultrasonic wave irradiated in step 3.

It is determined whether a stable cloud cavitation has been generated (step 5). Since the process of Step 3 is completed in a very short time, for example, 50 μs, the monitoring of cavitation generation is after Step 4. This is because it takes about 50 μs from generation of sound waves from cavitation to reception. Of course, this is not the case when this technique is used in different systems, and it is desirable to perform this process immediately after step 3, if possible. Here, for example, cavitation monitoring is performed using a characteristic sound wave when cavitation occurs or a characteristic sound wave from stable cavitation. If it is determined that stable cavitation has been generated, the process proceeds to step 6. If it is determined that stable cavitation has not been generated, the process returns to step 2.

It is determined whether the collapse position and / or collapse time of the cavitation bubble is correct (step 6). From the reception timing of the sound wave due to the collapse pressure, it can be confirmed whether or not the collapse has occurred at a position separated by the focal length. For example, it is possible to perceive a state in which collapse occurs in the side lobe before the focus. Furthermore, when it is determined that the collapse position of the cavitation bubble is correct, the process proceeds to step 7. If it is determined that the collapse position of the cavitation bubble is not correct, the process returns to step 2.

It is determined whether the collapse pressure of the cavitation bubble is appropriate (step 7). The collapse pressure at the focal point can be estimated from the pressure amplitude of the sound wave and / or the magnitude of the pressure due to the collapse pressure. This makes it possible to check whether the pressure (or pressure amplitude) necessary for crushing is obtained. If it is determined that the collapse pressure is appropriate, the process proceeds to step 8. If it is determined that the collapse pressure is not appropriate, the process returns to step 2.

It is determined whether the remaining bubbles are sufficiently small (step 8). By receiving sound waves from the residual bubbles after the collapse, the state of the residual bubbles can be monitored. The reception of sound waves from the bubbles may be reception only, transmission / reception, or a combination thereof.

[B-4] Monitoring of cavitation bubble generation Whether or not stable cloud cavitation is generated is determined by changing the sound pressure amplitude, stabilizing the sound pressure amplitude, detecting the harmonic signal generated from the bubble, or even low frequency. Thus, a plurality of methods such as whether or not a cloud collapse signal is actually obtained can be considered. These pieces of information can be acquired by processing the received sound pressure signal from the cavitation bubble.

One preferred example of a normal cavitation control cycle consists of (1) the occurrence of cavitation, (2) the generation of stable cloud cavitation, (3) the collapse of stable cloud cavitation, and (4) the disappearance of cavitation. Of these, the processes (1), (2), and (3) interact with the generation of stable cloud cavitation, and it is possible to check the generation of stable cloud cavitation with this process. .

In (1), the occurrence of cavitation is detected, and if it occurs, it can be predicted how long the irradiation time will generate stable cloud cavitation. (2) confirms whether cloud cavitation has stabilized. However, if it is difficult to detect sound waves from stable cloud cavitation, it is possible to use the feature that it is difficult to detect.In addition, in order to increase the accuracy, confirmation in the processes (1) and (3) is also possible. It will be important. In (3), it can be confirmed that a stable cloud cavitation would have been generated as a result if a database-like (or sufficiently large) collapse occurred.

As a specific determination method, the determination is performed using the pressure of the sound wave and the frequency component. The use of the pressure value will be described with reference to FIG. FIG. 7 shows the relationship between the sound pressure of the reception signal of the sound emitted from the cavitation cloud and time. As shown in FIG. 7, when the cloud is stabilized, a change is observed in a signal during irradiation of high-frequency ultrasonic waves. For example, in FIG. 7, after the pressure amplitude once increases with fluctuations, the value is decreased with time and stabilized at a substantially constant pressure amplitude. By monitoring such signal changes, it is determined whether stable cloud cavitation is generated. When the cloud collapses, an impact pressure corresponding to the strength of the collapse is observed. If the collapse according to the database occurs, it can be determined that a stable cloud cavitation could be generated as a result.

As for the frequency component, for example, since the sound pressure signal emitted in the cavitation generation process has a wide frequency band, it can be detected at a frequency lower or higher than the frequency of the irradiation ultrasonic wave. If this becomes stable cavitation, the frequency component is almost limited to a harmonic component that is an integral multiple of the irradiated ultrasonic wave. Therefore, it is determined by examining (1) the distribution of frequency components (spreading, variation, etc.) and (2) a specific frequency component (1/2 subharmonic component, double harmonic component, etc.) be able to.

When the determination as to whether stable cloud cavitation has been generated is “No”, the parameters to be subjected to feedback control are high-frequency ultrasonic parameters (high-frequency irradiation time, high-frequency output). FIG. 8 shows the relationship between the minimum output required for stable cloud cavitation and the minimum irradiation time. The generation of stable cloud cavitation depends on the output of high-frequency ultrasonic waves and the irradiation time of ultrasonic waves. Furthermore, the high frequency is also controlled. As a result, the size of the generated cloud cavitation can be changed, and the crushing force (power, range, etc.) can be changed.

If the determination of whether stable cloud cavitation is generated is “No”, for example, the high frequency irradiation time and / or the high frequency output is lengthened / enlarged. However, when the determination is “no”, the high-frequency irradiation time and / or the high-frequency output is not necessarily increased or increased. For example, when bubbles pass through a stable situation and are generated even in an unintended place, the high-frequency irradiation time and / or the high-frequency output is shortened / reduced.

Similarly, when it is determined that stable cloud cavitation has been generated when changing the frequency, the frequency is basically lowered, but bubbles are also generated in places where the target is not intended. If this is the case, it is necessary to increase the frequency in order to suppress damage to body tissues and increase efficiency. With respect to the fact that “bubbles are also generated at undesired locations”, it is possible to accurately determine the position of an image by performing imaging in the manner of ultrasonic diagnosis. However, since it is not always possible, (1) whether the sound wave from stable cloud cavitation is kept in a stable state, and (2) whether collapse pressure is obtained from multiple positions Therefore, it is considered that it is necessary to first determine what has occurred. There may be an embodiment in which the doctor finally makes a decision on (3) an ultrasound imaging image.

Strictly speaking, in the flowchart shown in FIG. 6, there is a loop for changing the high-frequency output / irradiation time. For the sake of simplicity, the procedure returns from step 8 to step 2, but first, the cloud must be generated even if the output / irradiation time of the ultrasonic parameter high frequency is changed and the output / irradiation time of the high frequency is sufficiently long. In this case, the positioning is re-executed from the position where the positioning is performed again. As other parameters, in the case of a phased array system, a change in phase between individual elements becomes a parameter.

[B-5] Monitoring of cavitation bubble collapse phenomenon By monitoring the cavitation bubble collapse phenomenon, it is determined whether the collapse position is appropriate or the collapse pressure is appropriate. In the determination of the collapse position, "Check whether collapse occurs at a position that is away from the focal distance from the reception time of the sound wave by the collapse pressure" is to measure the time from the transmission of the low frequency to the reception of the collapse pressure. To do. The time may be measured directly. For example, since the irradiation time of the high frequency is known, the time may be measured indirectly by measuring the time from the transmission of the high frequency.

When the collapse position of the cavitation bubble is not correct, the position of the apparatus is adjusted by feedback control in the case of manual positioning. In the case of the phased array method, the phase of each element is also a parameter as a positioning parameter.

The collapse pressure at the focal point is estimated from the relationship between the crushing efficiency of the stone and the received sound pressure. (Since the decay pressure itself cannot be measured, the received sound pressure is considered to be a parameter dependent on the decay pressure). The final information we want to obtain is the efficiency of stone crushing and the amount of damage to the body tissue. Since these both have a strong correlation with the decay pressure, it is also possible to create a database of each relationship via the decay pressure predicted from the received sound pressure. It is also possible to create a database of these relationships.

If an appropriate collapse pressure is not obtained, the feedback control targets include low-frequency output, changing the wave number, changing the time constant of the low-frequency rise, and the phase of the low-frequency rise. Changing the frequency of the low frequency. In addition to such low-frequency parameters, any one of a high-frequency parameter, a repetition frequency, positioning, phase correction (if a device capable of phase correction), or a combination of a plurality of parameters is also a control target. For example, the low-frequency parameter is first adjusted, and if an appropriate collapse pressure is not yet obtained, the target state is achieved in combination with the high-frequency parameter, positioning, phase correction, and the like.

[B-6] Monitoring of Cavitation Residual Bubbles In the present technology, one of the points is to use cavitation only in a narrow area. However, residual bubbles after the collapse of cavitation are generated or diffused in areas other than the area where stable cloud cavitation is generated, so even if the cycle starting from high frequency is repeated as it is, it becomes impossible to control in the local area End up. Therefore, the most efficient is to start the next cycle when the remaining bubbles are so small that they can be ignored. Therefore, residual bubbles are monitored, and the time until the next cycle (that is, the repetition frequency) is determined.

The state of residual bubbles is monitored by receiving sound waves from the residual bubbles after collapse. The state of residual bubbles means the size and total volume of residual bubbles. These parameters can be predicted from the magnitude of the collapse pressure (sound wave) from the residual bubbles and the time interval at which the collapse pressure occurs. Furthermore, an effective technique is to monitor the state of residual bubbles by irradiating the residual bubbles with ultrasonic waves with a strength that does not induce the generation and growth of residual bubbles and receiving sound waves reflected from the residual bubbles. . The magnitude of the collapse pressure from the residual bubbles directly indicates the volume of the residual bubbles. This is because the collapse pressure of a single bubble increases as the bubble radius increases. Moreover, the fact that the generation time of the collapse pressure is late and that the interval between the generation times of the collapse pressure is long also means that the volume of the residual bubbles is large. This is because if the bubble is large, the natural frequency of the bubble vibration naturally decreases.

If the disappearance of the cavitation bubbles is determined to be insufficient by monitoring the residual bubbles, the frequency is reset again to be low. Further, when it is determined that the disappearance of the cavitation bubbles is sufficiently fast, the repetition frequency is reset higher.

The relationship between monitoring of residual bubbles and resetting of the repetition frequency will be described. If there are many residual bubbles (larger), the repetition frequency must be lowered. Conversely, if there are few residual bubbles, the repetition frequency can be increased to increase the crushing efficiency. If the repetition frequency can be doubled, the treatment time will be reduced to 1/2, and this process will directly affect the crushing efficiency, so this process is a very important sequence.

FIG. 11 shows a time chart of ultrasonic irradiation and ultrasonic reception protocols. The interval between one pulse consisting of two-stage ultrasonic irradiation according to the present invention has a waiting time of 10,000 to 40,000 μs, excluding the monitoring time of cavitation bubbles. Therefore, it is possible to monitor the calculus body and surrounding tissue by irradiating 50-200 rasters of ultrasonic waves of 5 kHz PRF (pulse repetition frequency) using the waiting time.

[C] Outline of Example A cavitation behavior database (characteristics of cavitation behavior in a series of schemes) by high-frequency ultrasonic waves and low-frequency ultrasonic waves is created, and actual collapse behavior confirmation is performed according to the database. An experiment was conducted.
In particular,
(1) Creation of cavitation behavior database (high frequency phase);
Three types of cavitation behavior in the high frequency phase (Figs. 14, 15, 16)
(2) Sound pressure signal acquisition according to cavitation behavior (high frequency phase);
Examples of correspondence with high-frequency phase acoustic wave monitoring and three types of cavitation behavior (FIGS. 17, 18, 19, and 20)
(3) Creation of collapse pressure database (low frequency phase);
Correspondence between collapse pressure detection in low frequency phase and three types of cavitation behavior (FIGS. 21 and 22);
Extraction of conditions that lead to the optimal collapse pressure by monitoring the collapse pressure in the low frequency phase (FIG. 23);
(1), pressure sensitive sheet experiment and calculus crushing experiment based on (2), (3) (FIGS. 24 and 25);
Went.
In the high-frequency phase, cavitation was classified into three patterns, low, medium and high, according to the output level, and the characteristic monitoring sound pressure waveform corresponding to the classification was measured. Furthermore, it was clarified that the collapse pressure is optimally generated at medium output among the three types, and an example of a database for monitoring the collapse pressure in the low frequency phase was created. Based on these results, two types of confirmation tests were conducted: confirmation of a two-dimensional high pressure generation region using a pressure sensitive sheet and calculus crushing experiment.

[C-1] Experimental Device FIG. 13 is a schematic diagram of the experimental device used in this example. The experimental device is an experimental system in which an ultrasonic sensor is arranged at a position simulating monitoring from outside the body. FIG. 13 is a schematic diagram of an experimental apparatus used in this example. As the ultrasonic wave generation source, a concave PZT transducer having an aperture diameter of 100 [mm] and a focal length of 80 [mm] was used. The resonant frequency of the transducer is 555 [kHz] and has a fourth harmonic mode at 3.89 [MHz]. The high frequency and low frequency of cavitation control use the above two frequencies, that is, 3.89 [MHz] in the high frequency phase and 555 [kHz] in the low frequency phase.
A high-speed camera IMACON2000 (exposure 10 [nsec], interframe 10 [ms] in this experiment) was used for photographing cavitation behavior. A concave hydrophone with an aperture diameter of 12 [mm] and a focal length of 78.3 [mm] was used to monitor the sound pressure emitted from the cavitation. This concave hydrophone has almost the same focal length as the PZT transducer and can receive the sound pressure due to the cavitation phenomenon occurring at the focal point with high sensitivity. Since it is used as a Detector, it will be abbreviated as PCD hereinafter.) The resonant frequency of PCD is 20 [MHz], and it has a flat response and sufficient sensitivity in the <10 [MHz] band that is the subject of this experiment.

[C-2] Classification of cavitation bubbles in the high frequency (3.89 [MHz]) phase (high frequency phase database)
FIG. 14 shows the result of photographing a state of bubbles generated and growing on a wall surface in a high frequency phase of 3.89 [MHz] with a high-speed camera. The behavior of cavitation bubbles on the solid wall surface of the ultrasonic irradiation time 0-130 [μs] (0-506 [period]) at various ultrasonic outputs. The ultrasonic output (vertical axis) in the graph is the maximum negative pressure at the focal point (| p_ | = 4.8-11.7 [MPa]). This result shows that the behavior of the cavitation bubble group is large and can be classified into three types.
That is,
(A) Low sound pressure range (| p_ | <6.5 [MPa]): A state in which cavitation has not occurred or fine cavitation that cannot be confirmed by the camera has occurred;
(B) Medium sound pressure range (7.4 <| p_ | <9.6 [MPa]): A state in which a group of bubbles (cloud cavitation) maintaining a stable shape and size of a semi-elliptical sphere is generated;
(C) High sound pressure range (10.5 [MPa] <| p_ |: The state where cavitation with unstable shape and size occurs, especially around the semi-elliptical spherical bubbles that occur in the mid sound pressure range. In a state where a bubble or a group of bubbles, which are generated irregularly, have a relatively large diameter;
It is.
These behaviors are closely related to the sound pressure emitted from the cavitation bubbles and the collapse pressure in the low frequency phase. 15 and 16 show this classification in detail.
Note that the sound pressure ranges of (A), (B), and (C) have values as described above in this figure, but these threshold values are the state of the medium (dissolved gas concentration, type of liquid, liquid Temperature, bubble nucleus concentration, saturated vapor pressure, atmospheric pressure, impurity concentration, etc.), and the acoustic impedance and roughness of the solid wall surface. Therefore, the absolute value itself is not important, but it is important to note that the “characteristic” that the cavitation behavior changes by raising the ultrasonic output (A) → (B) → (C) is important. Keep it. This is because the cavitation state can be specified by monitoring the “characteristic response” as long as the “characteristic” and the “characteristic response to the characteristic” are known. An example of monitoring “characteristic response” corresponding to the three states (A), (B), and (C) in this high frequency phase is shown in FIGS.

[C-3] Cavitation bubble group typical length with respect to high frequency ultrasonic irradiation time (time-diameter graph)
FIG. 15 shows the result of measuring the representative length in the ultrasonic wave propagation direction (the normal direction of the solid wall surface) in a photograph of the cavitation bubble group in the same photographing as in FIG. That is, the length corresponding to the horizontal axis direction in FIG. 14 is measured. The conditions are the same as in FIG. 14, and the measurement results in (A) Low sound pressure range: 4.7 [MPa], (B) Medium sound pressure range: 8.7 [MPa], (C) High sound pressure range: 11.7 [MPa] It has become. The horizontal axis in FIG. 15 is the ultrasonic irradiation time (however, the time when the first ultrasonic wave is transmitted from the transducer is zero, so the time when the ultrasonic wave reaches the focal point is approximately 54 [μsec]). The cavitation bubbles are growing at each output. In the figure, “◯” indicates the length of a semi-elliptical spherical cavitation bubble group growing from the solid wall surface, and the representative length of cavitation that can be regarded as one bubble group in contact with the solid wall surface is measured. In addition, the “▲” mark in the figure has a length including the secondary cavitation generated so as to cover the semi-elliptical spherical bubbles.
(A) In the “low sound pressure range”, the bubble group has not been confirmed even after 100 [μsec] in the graph. Cavitation bubbles begin to be identified after passing 110 [μsec] and grow with time, but the final representative cavitation length is short, about 30-40 [μm].
(B) In the “medium sound pressure range”, the bubbles form a stable shape and size. Cavitation bubbles begin to be confirmed at 80 [μsec], and stable cavitation bubbles of about 50-60 [μm] are formed at 130 [μsec]. However, there are cases where secondary cavitation bubbles are generated from around 150 [μsec] so as to cover a group of semi-elliptical spherical bubbles having a stable size.
(C) In the “high sound pressure region”, secondary cavitation bubbles are generated so as to cover the periphery of the semi-elliptical spherical bubbles immediately after the generation of cavitation bubbles (85 [μsec]). Since the presence of such irregular cavitation bubbles may hinder effective high-pressure concentration on the solid wall surface, in the present technology, this sound pressure region is generally not preferable from the viewpoint of control. Conceivable. However, by using ultrasonic waves in a low frequency phase having a sufficiently low frequency and a sufficiently large pressure amplitude to collapse these bubble groups together, a large collapse pressure can be easily achieved. That is, the higher the frequency and the lower the frequency of ultrasonic output, the better, and the number of control steps can be reduced under such parameter conditions.

[C-4] Cavitation bubble group representative length with respect to high frequency ultrasonic irradiation time (output-diameter graph)
FIG. 16 is a graph in which the ultrasonic output is arranged on the horizontal axis with respect to the same result as FIG. The ultrasonic irradiation time was 114 [μsec], which is the time when 233 [cycle] was applied. According to this, the diameter of the bubble group gradually increases until the output of about 6.5 [MPa], and the stable shape and size of the semi-elliptical sphere of about 50-60 [μm] at about 7 [MPa]. It becomes a cavitation bubble group. On the other hand, from around 10 [MPa], secondary cavitation bubbles start to form. As described in FIG. 14, the threshold value varies depending on various surrounding conditions. In this condition, the low sound pressure range is up to 6.5 [MPa], and the medium sound pressure is from 6.5 [MPa] to 10 [MPa]. It is possible to define a region of three states in which the cavitation bubble group is different from the high sound pressure region over 10 [MPa].

[C-5] Detection of sound emission pressure when cavitation occurs FIGS. 17A, 17B, and 17C show high-speed camera photography and emission when cavitation occurs at each frequency of 1.7, 2.8, and 3.9 [MHz]. It is a detection result of sound pressure. When the cavitation bubbles are confirmed in the photographed image, the emitted sound pressure is detected almost simultaneously.

[C-6] Waveform of emission sound pressure monitoring in high-frequency phase FIG. 18 shows the monitoring of sound emission pressure in the entire high-frequency phase. 18A, 18B, and 18C show the results of monitoring the sound pressure from the cavitation bubble group by the concave type transducer (in this case, the output is shown by the peak-to-peak amplitude of the function generator. 19, 20, and 24 are also experimented under the same conditions as in FIG. 18). As shown in FIG. 18A, no change is seen in the received signal in the low sound pressure range of 100 to 300 [mV]. From around 350 [mV], the sound pressure released from cavitation begins to be detected. As shown in FIG. 18B, the sound pressure emitted from cavitation is always present in the received signal in the mid-range sound pressure range of 400-600 [mV]. Detected. As shown in FIG. 18C, the received signal is detected even in the high sound pressure range of 700 to 1000 [mV], but the waveform fluctuates greatly, reflecting the generation of a bubble group having an irregular shape and size. ing. On the other hand, in the 400-600 [mV] region of the medium sound pressure range, the waveform of the received signal shows a stable amplitude and a broken line, corresponding to the generation of cavitation bubbles with a stable size and shape. it seems to do. These results include information as “characteristic responses” to three types of “characteristic generation forms” due to differences in sound pressure output of cavitation bubbles, and the quantification thereof is shown in FIGS. 19 and 20 below. An example of typical detection will be described.

[C-7] Example of monitoring by amplitude of sound pressure waveform: magnitude of amplitude of time average waveform FIG. 19 is a time average waveform of sound pressure released from a cavitation bubble group at each output in the same case as FIG. It shows the absolute value of the amplitude of. The time average waveform is obtained by accumulating 10 different sample reception waveforms of the same case with the same time and dividing by 10 samples. By performing time averaging, the amplitude of random noise can be relatively reduced. That is, the amplitude of the signal from the cavitation bubble group in a stable state is increased each time, and the amplitude of the signal from the cavitation bubble group that is irregular and random in time and phase is relatively small. There is expected. In FIG. 19, corresponding to the original waveform seen in FIG. 18, (A) In the low sound pressure range, no cavitation bubbles are generated or only a very small cavitation is generated, and thus no received signal is detected. ; (B) In the medium sound pressure range, semi-elliptical spherical cavitation bubbles are generated with a stable shape and size, so that signals with the same amplitude and phase are detected in the received signal every time. The amplitude of the time-average waveform is also stably large. (C) In the high sound pressure region, the irregular component is canceled, so that the pressure amplitude is smaller than that in the case (B). We obtained processing results synchronized with these three forms.
It can be seen that the cavitation bubble group in the focal region can be monitored by processing such a received signal.

[C-8] Example of monitoring based on frequency component of sound pressure waveform: FFT analysis of received sound pressure FIGS. 20A, 20B, and 20C show the sound emitted from a group of cavitation bubbles at the same output as in FIG. The pressure and its frequency component are shown. FIG. 20A corresponds to a low sound pressure range where only very small cavitation occurs, and the main frequency component at that time is only 3.9 [MHz] which is the transmission frequency. FIG. 20B corresponds to a medium sound pressure region in which a group of semi-elliptical spherical cavitation bubbles maintains a stable shape and size. At this time, a frequency component corresponding to a harmonic component such as 7.8 [MHz] is a transmission frequency. It has risen to a value close to the 3.9 [MHz] component. FIG. 20C corresponds to the high sound pressure region in which irregular secondary cavitation bubbles are generated so as to cover the periphery of the semi-elliptical spherical bubble group. Is disturbed, and the value of the component having a frequency lower than 3.9 [MHz] which is the transmission frequency is increased. As described above, since the received signal in PCD has characteristic frequency components corresponding to each of the three types in FIG. 18, the received signal is analyzed by frequency analysis, or a low-pass filter, a high-pass filter, a band It can be seen that the cavitation bubble group in the focal region can be monitored by applying a filter for frequency components such as a pass filter to the received signal.

[C-9] Detection of Collapse Pressure in Low Frequency Phase FIG. 21 shows an example of monitoring the collapse pressure in the low frequency (555 [kHz]) phase after finishing the high frequency ultrasonic wave. The upper part is the original waveform of the PCD received sound pressure in the low frequency phase, and the lower part is the one that cuts the reflected wave due to the low frequency component of 555 [kHz] from the received signal and extracts the collapse pressure itself of the cavitation bubbles. The pressure amplitude of the low frequency applied from the left to the right is increasing. In all cases, the high-frequency ultrasonic wave is 9.5 [MPa] (maximum negative pressure) in the middle sound pressure range, and is a condition for generating a semi-elliptical spherical cloud cavitation with a stable shape and size. Looking at the top, it can be seen that the collapse pressure of the bubbles is observed during the reception of the reflected low-frequency wave. It can also be seen that the received sound pressure of the bubble group collapse increases as the low-frequency sound pressure increases.

[C-10] Relationship between Cavitation Bubble Group Generated in High Frequency Phase and Collapse Pressure FIG. 22 shows the relationship between the cavitation bubble group and the collapse pressure. The horizontal axis of FIG. 22 is the pressure amplitude of “high frequency ultrasonic”. In addition, the magnitude of the collapse pressure “in the low frequency phase” with respect to the pressure amplitude of the high frequency ultrasonic wave and the diameter of the cavitation bubbles generated “in the high frequency ultrasonic wave” at that time are shown in the same graph. The collapse pressure graph shows the magnitude of the collapse pressure signal of the bubbles as seen in FIG. 21, taking 100 cases of samples for various high-frequency ultrasonic outputs, and averaging the absolute values. It is. FIG. 22 shows that the collapse pressure of the cavitation bubble group is also greatly related to the three types of cavitation forms in the high frequency phase. That is, (A) In the low sound pressure range (0-6.5 [MPa]), no cavitation bubbles are generated or only very small cavitation bubbles are generated, so no collapse pressure is observed in the low frequency phase. Or very small. (B) In the mid-sound pressure range (6.5-10 [MPa]), the cavitation bubbles gradually increase in size, and the magnitude of the collapse pressure increases accordingly, near 9 [MPa]. Take the maximum value at. This coincides with a region where a group of stable bubbles having a semi-elliptical spherical size and shape is generated. However, when it exceeds 9 [MPa], the magnitude of the collapse pressure starts to decrease. (C) In the high sound pressure range (10 [MPa] or more), the semi-elliptical spherical bubbles are covered with irregular secondary cavitation bubbles, and as a result, the bubbles are affected by low frequency ultrasonic waves of 555 [kHz]. The collapse cannot be effectively caused, and the collapse pressure gradually decreases. The process in which the magnitude of the collapse pressure decreases beyond 10 [MPa] corresponds to the region where secondary cavitation bubbles are generated.
As described above, it can be seen from the results of FIG. 22 that the three types of cavitation bubble groups generated in the high frequency phase have a great influence on the “characteristic” of the collapse pressure in the low frequency phase. Further, the results of FIG. 21 show that the magnitude of the collapse pressure increases as the ultrasonic output at low frequency is increased, but these are obtained in FIGS. 21 and 22. Together with the obtained results, it shows the characteristics of the collapse pressure in the low frequency phase. Again, in the result of this collapse pressure,
* High frequency ultrasound is in low sound pressure range: no collapse pressure detected;
* High-frequency ultrasonic waves are in the mid-sound pressure range: Collapse pressure gradually increases, and starts to decrease with the generation of secondary bubbles.
* High-frequency ultrasonic waves are in the high sound pressure range: Due to the influence of secondary bubbles, effective collapse cannot be obtained, and the collapse pressure is smaller than in the medium sound pressure range;
* Increasing the pressure amplitude of low frequency ultrasound increases the magnitude of the collapse pressure;
The “characteristic” itself is important, and the absolute value of the output threshold value that delimits each region is not important because it varies depending on the surrounding conditions. In the control, the output parameter is changed in the direction in which the optimum collapse pressure is obtained according to the “characteristic”. That is, it is sufficient that the outline of the characteristics can be referred to from the device. Here, the “rough shape of the characteristic” is a mapping result of how the magnitude of the collapse pressure is distributed in all the high-frequency and low-frequency ultrasonic output parameter regions. FIG. 23 shows an example of the mapping.

[C-11] Example of database of collapse pressure with respect to pressure amplitudes of ultrasonic waves of high frequency and low frequency Different characteristics of cavitation bubbles in the high frequency phase, characteristics of collapse pressure in the low frequency phase, which have been found so far. In view of this, FIG. 23 shows the result of measuring the magnitude of the collapse pressure, which shows the efficiency of the actual technique, for each of various outputs of high-frequency ultrasonic waves and various outputs of low-frequency ultrasonic waves.
For high-frequency ultrasonic output, the collapse pressure increases from the low sound pressure range to the medium sound pressure range, and the collapse pressure decreases when reaching the high sound pressure range. On the other hand, it shows the “characteristic of the present technology” seen in the previous examples that the collapse pressure increases as the output is increased. In this case, the optimum collapse pressure was obtained at a high frequency of 9.5 [MPa] and a low frequency of 30 [MPa]. In actual equipment, the parameter to be controlled is changed so as to reach the peak of this collapse pressure. Therefore, optimization can be performed.

[C-12] Pressure Sensitive Sheet Experiment FIG. 23 shows the result of mapping the collapse pressure by monitoring the disintegration pressure in the distance. A confirmation test was carried out to see if this actually coincided with the generation of high pressure on the solid wall in the focal region. As an object, an experiment was conducted in which a pressure-sensitive sheet exhibiting a color change with respect to high pressure was installed in the focal region, and the output of high-frequency and low-frequency ultrasonic waves was changed in the same manner as in FIG. As can be seen in FIG. 24, for the output of high-frequency ultrasonic waves, the collapse pressure increases from the low sound pressure range to the mid sound pressure range, and a large discoloration is seen at the center in the mid sound pressure range. On the other hand, when reaching the high sound pressure region, only the central part became a donut-shaped discoloration region where discoloration was not observed. This is because secondary cavitation bubbles prevented effective collapse of the bubble groups, and no large pressure was concentrated in the center. As for the output of low frequency ultrasonic waves, the results showed that the area of the discoloration area gradually increased as the output was increased. This agrees very well with the characteristics shown in the results of FIG. 23, and indicates that it is possible to control the present technology by performing monitoring. Fig. 24B is a cross-sectional view of the luminance distribution, showing strong color development at the center of the pressure-sensitive sheet in the middle sound pressure range of 400 mV, and weakening of color development in the center at 800, 1000 mV in the high sound pressure range. It is confirmed that

[C-13] Results of stone crushing experiment in each sound pressure range Finally, a model stone crushing experiment was conducted in the high-frequency range of low sound pressure, medium sound pressure, and high sound pressure. The results are shown in FIG. The result was that the medium sound pressure range crushes stones more efficiently than the low sound pressure range and the high sound pressure range.

The present invention is effective not only in medical applications such as stone crushing but also in industrial applications such as ultrasonic cleaning and cavitation peening.

It is a whole system diagram of an ultrasonic irradiation device. A schematic diagram of a cavitation control method and an outline of an ultrasonic pulse waveform used for acoustic cavitation control are shown. The behavior of cavitation when acoustic cavitation by focused ultrasound is actually generated and collapsed using the above method is shown. It is a figure which shows the result of applying this method to a model stone. It is a figure which shows the structure of the calculus crushing system which concerns on this invention. It is a flowchart of the calculus crushing method using the collapse pressure of cavitation. It is a figure which shows the sound discharge | released from a cavitation cloud, a horizontal axis is time and a vertical axis | shaft is a sound pressure. (1) When the cloud is stabilized, the signal in the high frequency region changes. → Stable cloud monitoring is performed. (2) When the bubble cloud collapses, an impact pressure corresponding to the strength of the collapse is observed. → Crushing efficiency is judged. (3) Residual bubbles collapse after 100-200 μs and a signal is detected. → The optimum repetition frequency is determined from the signal strength and decay time. It is a figure which shows the minimum output required for stable cloud cavitation. A vertical line A indicates a threshold value (minimum applied voltage) for occurrence of cavitation, and a vertical line B indicates a threshold value (applied voltage) for stable cloud cavitation. The applied voltage physically has a one-to-one correspondence with the pressure amplitude of the ultrasonic wave. It is a figure which shows the minimum irradiation time required for stable cloud cavitation. A vertical line C indicates a stable cloud cavitation threshold (irradiation time). It is a flowchart explaining the monitoring rig of stable cloud cavitation. It is a figure which shows monitoring of collapse / disappearance of a cavitation bubble. It is a figure which shows an ultrasonic irradiation and reception protocol. It is the schematic which illustrates a sound wave receiving part. It is the schematic of an experimental apparatus. The classification of cavitation in the high frequency phase (high frequency pressure amplitude 4.8-11.7 [MPa]) is shown. The representative length of cavitation bubble group for the ultrasonic irradiation time in the low sound pressure range 4.7 [MPa] is shown. ○: Semi-elliptical spherical cloud cavitation; ▲: Cavitation (Shielding cavitation) covering semi-elliptical spherical cloud cavitation. In the low sound pressure range 4.7 [MPa], the bubble cloud has not grown. The typical cavitation bubble group length for the ultrasonic irradiation time in the middle sound pressure range of 8.7 [MPa] is shown. ○: Semi-elliptical spherical cloud cavitation; ▲: Cavitation (Shielding cavitation) covering semi-elliptical spherical cloud cavitation. The medium sound pressure range of 8.7 [MPa] has reached a stable size around 130 [μs]. The representative length of the cavitation bubble group with respect to the ultrasonic irradiation time in the high sound pressure region 11.7 [MPa] is shown. ○: Semi-elliptical spherical cloud cavitation; ▲: Cavitation (Shielding cavitation) covering semi-elliptical spherical cloud cavitation. In the high sound pressure region 11.7 [MPa], a large number of bubbles are generated so as to cover the semi-elliptical spherical bubbles immediately after ultrasonic irradiation. The representative length of a cavitation bubble group with respect to the pressure amplitude of high frequency ultrasonic waves (horizontal axis: pressure amplitude of ultrasonic waves of high frequency, vertical axis: bubble group representative length) is shown. It shows the detection of the sound pressure emitted when cavitation occurs at each frequency of 1.7 [MHz]. It shows the detection of the sound pressure released when cavitation occurs at each frequency of 2.8 [MHz]. The detection of the sound pressure released when cavitation occurs at each frequency of 3.9 [MHz] is shown. Regarding the sound pressure emitted in the low sound pressure range, the experimental results at function generator output amplitude: 100, 200, 300 [mV] are shown. The experimental results for function generator output amplitude: 400, 500, 600 [mV] are shown for the sound pressure emitted in the middle sound pressure range. The experimental results at the function generator output amplitude: 700,800 900,1000 [mV] are shown for the sound pressure emitted in the high sound pressure range. Example 1 of monitoring cavitation dynamics by sound pressure waveform: Indicates the amplitude of time averaged waveform. (A) No signal is detected in the low sound pressure range. (B) Since the signal has the same amplitude and phase in the middle sound pressure range, the time-average waveform has a stable amplitude. (C) Since the irregular component is canceled in the high sound pressure range, the pressure amplitude is reduced. Example 2 of monitoring cavitation dynamics using sound pressure waveform: Shows frequency analysis (FFT), corresponding to low sound pressure range. Example 2 of monitoring cavitation dynamics by sound pressure waveform-2: Shows frequency analysis (FFT) and corresponds to the mid sound pressure range. Example 2 of monitoring cavitation dynamics by sound pressure waveform-2: Shows frequency analysis (FFT), corresponding to high sound pressure range. This shows the detection of the decay pressure in the low frequency phase (upper part: raw waveform of received sound pressure, lower part: waveform after removal of the low frequency (555 [kHz]) component). In all cases, the high-frequency ultrasonic wave is 9.5 [MPa] (maximum negative pressure) in the middle sound pressure range, and is a condition for generating a semi-elliptical spherical cloud cavitation with a stable shape and size. After the high frequency strike, the collapse pressure of the bubbles is observed during reception of the low frequency reflected wave. It can also be seen that the received sound pressure of the bubble group collapse increases as the low-frequency sound pressure increases. The relationship between the cavitation bubbles generated in the high frequency phase and the collapse pressure in the low frequency phase is shown. An example of a collapse pressure database with respect to the pressure amplitude of ultrasonic waves at high and low frequencies is shown. A pressure sensitive sheet experiment is shown. FIG. 24A shows the experimental results for the amplitudes at high and low frequencies. A pressure sensitive sheet experiment is shown. FIG. 24B is a cross section of the luminance distribution in the case of the low frequency 26.6 [MPa]. The results of stone crushing in each sound pressure range are shown. The left is the “low sound pressure range”, the center is the “medium sound pressure range”, and the right is the “high sound pressure range”. It shows a semi-elliptical spherical cloud cavitation with a stable size and shape created by focused ultrasound at various frequencies (1.67, 2.75, 3.27, 3.82 MHz). FIG. 26B is a plot of representative length versus frequency for cloud cavitation as shown in FIG. 26A.

Claims (31)

A first step of irradiating an object having liquid in at least a part of its surroundings with high-frequency ultrasonic waves to generate cavitation bubbles in a region including the object;
A second step of irradiating the object with low-frequency ultrasonic waves, causing the cavitation bubbles to collapse, and imparting high energy to the object;
A third step which is an interval time after the second step;
A first step comprising:
A second step of acquiring a sound wave emitted from the cavitation bubble and controlling the ultrasonic wave irradiation condition by processing the sound wave;
An ultrasonic irradiation method comprising: The method according to claim 1, wherein the third step of the first step is performed after the second step so as not to irradiate the object with ultrasonic waves or to induce generation and growth of bubbles. An ultrasonic irradiation method, characterized by being an interval time during which only a sound wave is irradiated. 3. The method according to claim 1, wherein the second step can be performed at any time of the first, second, and third steps of the first step, and sound waves generated from the cavitation bubbles. Is performed by receiving sound waves reflected from cavitation bubbles with respect to ultrasonic waves that are passively received and / or irradiated. 4. The method according to claim 1, wherein the signal processing of the second step includes a determination as to whether stable cavitation bubbles are generated by the first step of the first step, and is controlled by an ultrasonic wave. An ultrasonic irradiation method, wherein the irradiation condition is an output of high frequency ultrasonic waves and / or an irradiation time. 5. The ultrasonic irradiation method according to claim 4, wherein the controlled ultrasonic irradiation condition further includes a high frequency ultrasonic frequency. 6. The method according to claim 4, wherein the determination as to whether or not a stable cavitation bubble has been generated uses a pressure amplitude and / or a pressure magnitude of a sound wave reception signal from the cavitation bubble. A characteristic ultrasonic irradiation method. 7. The ultrasonic irradiation method according to claim 4, wherein the frequency component of the reception signal of the sound wave from the cavitation bubble is used to determine whether or not a stable cavitation bubble has been generated. 8. The ultrasonic wave according to claim 4, wherein whether or not stable cavitation bubbles are generated is determined by determining whether or not the generated cavitation bubbles are in a medium sound pressure range. Irradiation method. 9. The method according to claim 1, wherein the signal processing in the second step includes determining whether the collapse position and / or the collapse time of the cavitation bubble in the second step of the first step is appropriate, The ultrasonic irradiation method is characterized in that the controlled ultrasonic irradiation condition is positioning. The method according to claim 9, wherein the determination of whether the collapse position and / or the collapse time of the cavitation bubble is appropriate is performed by measuring a time from transmission of a low-frequency ultrasonic wave to reception of a sound wave due to collapse pressure. An ultrasonic irradiation method characterized by performing. 11. The method according to claim 1, wherein the signal processing in the second step includes determining whether the collapse pressure of the cavitation bubble in the second step of the first step is appropriate and controlled ultrasonic waves. Irradiation conditions include at least one of an output of a low frequency ultrasonic wave, a wave number, a rising time constant, a rising phase, and a frequency. The ultrasonic irradiation method according to claim 11, wherein the controlled ultrasonic irradiation condition further includes at least one of a high-frequency ultrasonic irradiation condition and positioning. 13. The method according to claim 11, wherein whether or not the collapse pressure of the cavitation bubble is appropriate is determined by measuring a pressure amplitude and / or a pressure magnitude of a sound wave reception signal based on the collapse pressure. An ultrasonic irradiation method characterized by the above. 14. The method according to claim 1, wherein the signal processing in the second step includes a determination as to whether or not the number of residual bubbles in the third step of the first step is sufficiently small, and is controlled by the ultrasonic irradiation conditions. Is the repetition frequency of the first step according to claim 1. 15. The ultrasonic irradiation method according to claim 14, wherein the determination is made based on a collapse pressure and / or a collapse time of residual bubbles. 15. The method according to claim 14, wherein the determination is reflected from the residual bubbles with respect to the ultrasonic ultrasonic wave irradiated in the third step of the first process and having an intensity that does not induce generation and growth of the bubbles. An ultrasonic irradiation method characterized by being performed by receiving a sound wave. 17. The ultrasonic irradiation method according to claim 1, wherein the processing of the sound wave generated from the cavitation bubble includes acquisition of an image of the cavitation bubble based on the sound wave. 18. The method according to any one of claims 1 to 17, further comprising the step of acquiring and signal-processing sound waves from the object and / or the environment surrounding the object. Sound wave irradiation method. 19. The method according to claim 18, wherein the signal processing obtains an image of the object and / or the surrounding of the object using a sound wave signal from the environment of the object and / or the object. An ultrasonic irradiation method comprising: The ultrasonic irradiation method according to claim 1, wherein the second step includes crushing of an object. 20. The ultrasonic irradiation method according to claim 1, wherein the second step includes peeling of a foreign substance from an object. The ultrasonic irradiation method according to claim 1, wherein the second step includes surface modification of an object. 20. The ultrasonic irradiation method according to claim 1, wherein the second step includes thermal modification of an object. An ultrasonic irradiation unit that irradiates the object with ultrasonic waves based on the set ultrasonic irradiation conditions;
A sound wave receiver;
A signal processing unit for processing a signal received by the sound wave receiving unit;
A control unit for controlling the ultrasonic irradiation conditions of the ultrasonic irradiation unit,
The ultrasonic irradiation unit irradiates a high frequency ultrasonic wave toward an object having liquid in at least a part of the periphery by the control unit, and generates cavitation bubbles in a region including the object, Irradiating the object with low-frequency ultrasonic waves, causing the cavitation bubbles to collapse, and controlling the object to give high energy;
The sound wave receiving unit receives sound waves emitted from the cavitation bubbles, and processes the received sound waves with the signal processing unit, so that the control unit controls ultrasonic irradiation conditions based on the signal processing result. An ultrasonic irradiation apparatus characterized by comprising the above. 25. The ultrasonic irradiation apparatus according to claim 24, wherein the sound wave receiving unit is an ultrasonic probe and / or a hydrophone. 26. The ultrasonic irradiation apparatus according to claim 24, wherein the signal processing unit includes a sound pressure analysis unit for the received sound wave. 27. The ultrasonic irradiation apparatus according to claim 24, wherein the signal processing unit includes a frequency analysis unit of a received sound wave. 28. The apparatus according to any one of claims 23 to 27, further comprising means for irradiating ultrasonic waves with an intensity that does not induce generation and growth of bubbles, and the object and / or surroundings of the object. An ultrasonic irradiation apparatus configured to process a reflected sound wave of the ultrasonic wave from an environment and / or a cavitation bubble by a sound wave receiving unit. 29. The ultrasonic irradiation apparatus according to claim 24, wherein the signal processing unit includes an image processing unit that obtains image information based on a received sound wave. 30. The apparatus according to claim 23, wherein the ultrasonic irradiation conditions are: output of high frequency ultrasonic waves, irradiation time of high frequency ultrasonic waves, frequency of high frequency ultrasonic waves, positioning of an ultrasonic irradiation unit with respect to an object. An ultrasonic irradiation apparatus comprising one or more selected from the group consisting of: repetition frequency, low frequency ultrasonic wave output, wave number, rise time constant, rise phase, frequency. The apparatus according to claim 30, wherein the apparatus includes a storage unit, and the storage unit stores information indicating a relationship between the ultrasonic irradiation condition and a physical condition. Ultrasonic irradiation device.