JP5954841B2 - Ultrasound medical device - Google Patents

Description

  The present invention relates to an ultrasonic medical device for diagnosing tissue coagulation.

  A treatment method is known in which, for example, a living body is irradiated with high intensity focused ultrasound (HIFU), and a treatment site such as a tumor is heated and coagulated using the acoustic energy.

  It is known that when a tissue is heated and solidified, the elastic modulus (Young's modulus) of the tissue increases before and after the solidification. In addition, since relatively strong ultrasonic waves such as HIFU generate radiation force in the traveling direction, for example, a displacement of about 10 to 100 μm (micrometer) is applied to the tissue at the focal point of the ultrasonic beam of HIFU. Can be given.

Therefore, it is possible to observe the coagulation of the tissue by applying a displacement to the tissue with relatively strong ultrasonic waves such as HIFU and measuring the decrease in the displacement due to the increase in the elastic modulus. For example, the ultrasonic wave of the HIFU is amplitude-modulated with the modulation frequency f _M and the intensity of the radiation force is changed to excite vibrations in the tissue at the focal site, and the displacement or velocity of the vibrations is measured by the ultrasonic diagnostic apparatus. .

HMI (Harmonic Motion Imaging) is a technique for detecting tissue coagulation using this principle and mapping the detection result on an image (see Patent Documents 1 and 2). Frequency of oscillation of the radiation force and organizations are called HMI from becoming 2 times the modulation frequency f _M.

US Patent Application Publication No. 2005/0004466 US Patent Application Publication No. 2007/0276242

  By the way, in the treatment using HIFU, it is desirable to appropriately control the HIFU in accordance with the coagulation situation at the treatment site. This is because the effects of attenuation and phase distortion on the focal sound pressure are different due to the fact that the acoustic characteristics of the propagation path differ depending on the individual patient in the irradiation of the HIFU to the living body. This is because it is difficult to optimize treatment parameters in advance because of changes in energy required for coagulation due to differences in cooling effect due to differences. For example, if it is possible to know the timing at which coagulation is started at the treatment site, the timing at which coagulation is completed to a target size, and the like, it is possible to control the irradiation of HIFU in accordance with those timings.

  Under such circumstances, the inventors of the present application have been researching and developing techniques for diagnosing tissue coagulation using ultrasonic waves.

  The present invention has been made in the course of research and development, and an object thereof is to provide an improved technique for diagnosing tissue coagulation using ultrasonic waves.

  A suitable ultrasonic medical apparatus for the above purpose includes a transmission unit that outputs a transmission signal of a displacement ultrasonic wave that periodically displaces a tissue, and a reception that receives a reception signal of a measurement ultrasonic wave from the periodically displaced tissue. A displacement measuring unit that measures the displacement of the tissue based on a reception signal of the measurement ultrasonic wave, a displacement processing unit that obtains displacement data indicating a periodic change of the displacement based on the measured displacement, And a coagulation diagnosis unit for diagnosing the coagulation of the tissue based on the displacement data.

  In the above apparatus, the ultrasonic waves for measurement have the same characteristics (frequency, waveform, intensity) as the ultrasonic waves for diagnosis in a general ultrasonic diagnostic apparatus, and are transmitted and received using a diagnostic ultrasonic transducer. can do. On the other hand, the ultrasonic waves for displacement are ultrasonic waves with relatively high intensity that can displace the tissue by the radiation force. The ultrasonic waves for displacement have a higher intensity than the ultrasonic waves for measurement. For example, high intensity focused ultrasonic waves (HIFU) are suitable specific examples of ultrasonic waves for displacement. In addition, when using intense focused ultrasound (HIFU) as the ultrasound for displacement, the tissue may be heated and solidified while the tissue is displaced by the intense focused ultrasound (HIFU).

  The apparatus periodically displaces the tissue with the ultrasonic waves for displacement, and obtains displacement data indicating the periodic change of the displacement. This makes it possible to diagnose the coagulation of the tissue based on the displacement data indicating the periodic change of the displacement related to the tissue.

  In a preferred embodiment, the transmission unit outputs a transmission signal of the modulated displacement ultrasonic wave, and the displacement processing unit displaces the displacement data along a time axis corresponding to the period of the modulation processing. And a coagulation diagnosis unit diagnoses coagulation of the tissue based on the displacement map.

  In a preferred embodiment, the displacement processing unit forms a displacement map showing a temporal change in displacement at each sampling point for a plurality of sampling points arranged in the sampling direction, and the coagulation diagnosis unit is based on the displacement map. Deriving the coagulation size in the sampling direction of the tissue.

  In a preferred embodiment, the coagulation diagnosis unit extracts a frequency component corresponding to the period of the modulation process by performing frequency analysis of the displacement map in the time axis direction, and based on the extracted frequency component, the coagulation size Vs of the tissue. It is characterized by deriving.

  In a preferred embodiment, the coagulation diagnostic unit derives a coagulation size Vs in the tissue sampling direction based on a phase change in the sampling direction of the frequency component extracted for a plurality of sampling points.

  In a preferred embodiment, the coagulation diagnostic unit calculates a reduction rate of displacement for each sampling point based on the displacement map obtained at each diagnostic time over a plurality of diagnostic times, and The solidification size Ar in the sampling direction of the tissue is derived based on the decrease rate of the displacement of the tissue.

  In a preferred embodiment, the coagulation diagnosis unit derives a tissue coagulation size Vs based on a frequency component corresponding to the period of the modulation processing obtained from the displacement map, and calculates the displacement reduction rate obtained from the displacement map. Based on this, the tissue coagulation size Ar is derived, and the tissue coagulation size is determined by comprehensive determination based on the coagulation size Vs and the coagulation size Ar.

  The present invention provides an improved technique for diagnosing tissue coagulation using ultrasound. For example, according to a preferred aspect of the present invention, it is possible to diagnose the coagulation of the tissue based on the displacement data indicating the periodic change of the displacement related to the tissue.

1 is a diagram showing an overall configuration of an ultrasonic medical apparatus suitable for implementing the present invention. 2 is a timing chart showing the operation of the ultrasonic medical apparatus in FIG. 1. It is a figure for demonstrating the specific example of the setting of a modulation frequency. It is a figure which shows a mode that the data from the phase 1 to the phase 13 are collected. 3 is a flowchart showing a specific example of the operation of the ultrasonic medical apparatus in FIG. 1. It is a figure which shows the specific example of a displacement map. It is a figure for demonstrating the change of the displacement map accompanying progress of coagulation. It is a figure which shows the example of a measurement of the coagulation size Vs based on a displacement map. It is a flowchart which shows the example of a measurement of coagulation size Ar based on a displacement map. It is a figure which shows the specific example of a displacement reduction rate map. It is a figure which shows the specific example of the treatment site | part P in a treatment area | region. It is a figure for demonstrating the reliability of coagulation size Ar.

  FIG. 1 is an overall configuration diagram of an ultrasonic medical apparatus (the present ultrasonic medical apparatus) suitable for implementing the present invention. This ultrasonic medical apparatus has a composite ultrasonic transducer 10, and the ultrasonic transducer 10 includes a HIFU transducer 10H and a diagnostic transducer 10D.

  The HIFU vibrator 10H is a vibrator that transmits strong focused ultrasound (HIFU), and includes, for example, a plurality of vibration elements arranged two-dimensionally. For example, the HIFU transducer 10H forms a therapeutic ultrasonic beam TB toward the treatment site P such as cancer or tumor, transmits a strong focused ultrasound, and heats and treats the treatment site P. Used.

  Further, the HIFU transducer 10H forms a displacement ultrasonic beam EB toward the treatment site P and transmits an ultrasonic wave for generating displacement, and generates a radiation force at the treatment site P to displace the tissue. The displacement ultrasonic beam EB is a beam formed with such an intensity that an effective radiation force is generated at the treatment site P. For example, the treatment ultrasonic beam TB may be used as the displacement ultrasonic beam EB. Good. Of course, a displacement ultrasonic beam EB different from the therapeutic ultrasonic beam TB may be used.

  On the other hand, the diagnostic transducer 10D includes, for example, a plurality of vibration elements arranged two-dimensionally. For example, a comparison for forming an ultrasound image on a subject (patient) having a treatment site P is performed. Send and receive weak ultrasonic waves. That is, ultrasonic waves having the same intensity (energy) as that of a known general ultrasonic diagnostic apparatus are transmitted and received.

  In addition, the diagnostic transducer 10D forms a measurement ultrasonic beam MB toward the treatment site P, transmits and receives measurement ultrasonic waves, and obtains a reception signal along the measurement ultrasonic beam MB. The received signal obtained along the measurement ultrasonic beam MB is used to measure the displacement at the treatment site P due to the radiation force of the displacement ultrasonic beam EB.

  In addition, the ultrasonic transducer | vibrator 10 makes the inside surface dented in bowl shape the vibrator surface, for example. Then, for example, the diagnostic transducer 10D is provided at the bottom portion located in the center of the inside which is recessed in the bowl shape, and the HIFU transducer 10H is provided so as to surround the diagnostic transducer 10D. Note that the shape of the transducer surface of the ultrasonic transducer 10 is not limited to a bowl shape, and it is desirable that the shape be adapted to, for example, a therapeutic application. Moreover, all the vibration elements or some vibration elements may be used in combination for both HIFU use and diagnosis use.

  The measurement diagnostic block 20 includes a transmission / reception unit 22 that controls transmission / reception of the diagnostic transducer 10D. The transmission / reception unit 22 outputs a transmission signal corresponding to each of the plurality of vibration elements constituting the diagnostic transducer 10D, thereby controlling the diagnostic transducer 10D to form a transmission beam. A received signal is obtained along the received beam by performing a phasing addition process on the received signal obtained from each of the vibration elements. That is, the transmission / reception unit 22 includes a function of a transmission unit (transmission beamformer) and a function of a reception unit (reception beamformer).

  The transmission / reception unit 22 scans a diagnostic ultrasonic beam in a three-dimensional space or cross section including the treatment site P and collects reception signals for images. Then, based on the collected received signals, the ultrasonic image forming unit 28 forms image data of a three-dimensional ultrasonic image or a two-dimensional tomographic image, and an ultrasonic image corresponding to the image data is displayed on the display unit 50. Is displayed.

  The user (examiner) confirms the position of the treatment site P from the ultrasonic image displayed on the display unit 50, and uses the operation device (not shown) to obtain the position information of the treatment site P in this ultrasonic medical apparatus. To enter. Of course, the ultrasonic medical apparatus may obtain the position information by confirming the position of the treatment site P by image analysis processing or the like on the ultrasonic image.

  In addition, the transmission / reception unit 22 controls the diagnostic transducer 10D to form the measurement ultrasonic beam MB, and obtains a reception signal along the measurement ultrasonic beam MB. And the displacement measurement part 24 measures the displacement in the treatment site | part P based on the received signal obtained along the measurement ultrasonic beam MB. Further, the displacement map forming unit 25 functions as a displacement processing unit that obtains displacement data indicating a periodic change of the displacement based on the displacement measured by the displacement measuring unit 24. The displacement map forming unit 25 forms a displacement map described in detail later as the displacement data. Then, the coagulation measurement unit 26 measures the coagulation of the tissue at the treatment site P based on the displacement map. Specific processing in the displacement measuring unit 24, the displacement map forming unit 25, and the coagulation measuring unit 26 will be described in detail later.

  On the other hand, the therapeutic radiation block 30 includes a therapeutic transmitter 32, and the therapeutic transmitter 32 outputs a transmission signal corresponding to each of a plurality of vibration elements constituting the HIFU transducer 10H, thereby HIFU. The ultrasonic transducer for treatment 10H is controlled to form a therapeutic ultrasonic beam TB. The therapeutic transmission unit 32 is controlled by the control unit 40, and for example, a therapeutic ultrasonic beam TB with a focus set in the treatment site P is formed.

  The therapeutic radiation block 30 includes a displacement transmitter 34. The displacement transmitter 34 outputs a transmission signal corresponding to each of the plurality of vibration elements constituting the HIFU transducer 10H, thereby HIFU. The displacement transducer 10H is controlled to form the displacement ultrasonic beam EB. The displacement ultrasonic beam EB is subjected to modulation processing, and the modulation frequency in the modulation processing is controlled by the modulation frequency control unit 36. The modulation frequency control unit 36 is controlled by the control unit 40.

  When intense focused ultrasound (HIFU) is transmitted along the therapeutic ultrasound beam TB and the treatment site P is heated, the tissue of the treatment site P is coagulated. It is known that the elastic modulus (Young's modulus) of the tissue increases before and after the solidification. In order to know the change in the elastic modulus of the tissue, the ultrasonic medical device generates an radiating force by transmitting an ultrasonic wave along the displacing ultrasonic beam EB, and at the treatment site P due to the radiating force. Measure tissue displacement. The measurement of the displacement is performed based on the received signal obtained along the measurement ultrasonic beam MB.

  Each unit in the measurement diagnosis block 20 and each unit in the treatment radiation block 30 can be realized by using hardware such as a processor or an electronic circuit, for example. The control unit 40 is configured by, for example, hardware having a calculation function and software (program) that defines the operation thereof. The display unit 50 is, for example, a liquid crystal display.

  The measurement diagnostic block 20 may be realized by a general ultrasonic diagnostic apparatus. The ultrasonic medical apparatus may be embodied by a system that combines an ultrasonic therapeutic apparatus corresponding to the therapeutic radiation block 30 and an ultrasonic diagnostic apparatus corresponding to the measurement diagnostic block 20.

  The overall configuration of the ultrasonic medical apparatus is as described above. Next, functions and the like realized by the ultrasonic medical apparatus will be described. In addition, about the structure (each part which attached | subjected the code | symbol) shown in FIG. 1, the code | symbol of FIG. 1 is utilized in the following description.

  FIG. 2 is a timing chart showing the operation of the ultrasonic medical apparatus (present ultrasonic medical apparatus) of FIG.

  The main trigger is a signal indicating the start timing of treatment by high intensity focused ultrasound (HIFU). For example, each part in the ultrasonic medical apparatus from the control unit 40 according to the operation of starting treatment by the user (examiner). Is output.

  The frame trigger is a signal indicating the start of a frame of the measurement ultrasonic beam MB. The transmitter / receiver 22 sequentially forms a plurality of measurement ultrasonic beams MB toward the treatment site P, for example, from the rising timing of the frame trigger. For example, between two frame triggers, 10 transmission beams are formed toward the treatment site P, and 20 reception beams are formed, two for each transmission beam. Of course, the number of transmission beams and reception beams is not limited to the above specific example.

  The heating period signal is a signal indicating the heating process period of the treatment site P by the therapeutic ultrasound beam TB, and in the period from the rise to the fall of the heating period signal, for example, the treatment ultrasound beam is focused on the treatment site P. TB is formed.

  The measurement period trigger is a signal indicating the displacement measurement period, and the period from the rise to the fall of the measurement period trigger is the displacement measurement period.

  The modulation signal is a modulation signal used for modulation processing of the therapeutic ultrasonic beam TB, and is output from the modulation frequency control unit 36 to the displacement transmission unit 34, for example.

  The HIFU signal is a transmission signal of the therapeutic ultrasonic beam TB, and is obtained by the displacement transmission unit 34 by amplitude-modulating a continuous wave having a frequency of about 2 MHz, for example, according to the modulation signal.

  The modulation signal has an amplitude of 0 (zero) in the measurement period from the rise to the fall of the measurement period trigger. As a result, the amplitude of the HIFU signal also becomes 0 in the measurement period, and the therapeutic ultrasonic beam TB in the measurement period. Transmission is stopped.

  The measurement period trigger is output with a delay amount (Delay) with respect to the frame trigger. This delay amount is appropriately adjusted by the user, for example. Accordingly, one or several measurement ultrasonic beams MB that fall within the measurement period among a plurality of measurement ultrasonic beams MB (for example, 20 reception beams) formed between two frame triggers. Are selectively used for measurement.

This ultrasonic medical apparatus excites vibration in the tissue at the focal site by amplitude-modulating the displacement ultrasonic beam EB for generating displacement at the modulation frequency f _M and changing the intensity of the radiation force. The displacement is measured using the ultrasonic beam for measurement MB. At that time, the modulation frequency control unit 36 controls the modulation frequency f _M of the displacement ultrasonic beam EB. Instead of the amplitude modulation, frequency modulation of the modulation frequency f _M may be utilized.

  FIG. 3 is a diagram for explaining a specific example of setting the modulation frequency. In this ultrasonic medical apparatus, for example, the modulation frequency is determined by the following equation.

    [Expression 1] Modulation frequency (Hz) = {frame rate (Hz) / prime number} × natural number N

  The frame rate (Hz) and the prime number in Equation 1 are appropriately set according to, for example, the specifications of the apparatus and the treatment target. A specific example in which the frame rate is 500 Hz and the prime number is 13 will be described below.

  When the frame rate is 500 Hz and the prime number is 13, the modulation frequency (Hz) obtained by the equation (1) is the modulation frequency 1 (38.46 Hz) when the natural number N is the identification number (modulation frequency N) of the modulation frequency. , Modulation frequency 2 (76.92 Hz),..., Modulation frequency 5 (192.30 Hz),.

  The frame rate is a cycle of the frame trigger (FIG. 2), and this is a cycle in which the measurement of displacement is repeated at the same position by the measurement ultrasonic beam MB. That is, the frame rate is the sampling rate in the displacement measurement.

  In FIG. 3, <A> indicates the phase of one period of the modulation signal, and the phase number (phase 1 to phase 13) indicates the phase position (phase) when one period of the modulation signal is equally divided by the prime number 13. Angle). <B> shows the correspondence between the phase number (phase 1 to phase 13) and the sampling number (SP1 to SP13) which is the data acquisition order for each modulation frequency.

  If the prime number is 13, the modulation frequency 1 (38.46 Hz) is 1/13 of the frame rate (500 Hz) according to Equation (1). That is, the sampling rate in the displacement measurement is 13 times the modulation frequency 1. Therefore, when the data of sampling number 1 (SP1) is obtained in phase 1 with the arrangement of the phase numbers shown in <A>, the data of sampling number 2 (SP2) is obtained in phase 2, and then <B>. As shown, data is obtained in the order of phase 3, phase 4, phase 5,..., Sampling number 13 (SP13) data is obtained in phase 13, and 13 data for one period are collected. The This state is shown in FIG.

  Returning to FIG. 3, the modulation frequency 2 (76.92 Hz) is 2/13 of the frame rate (500 Hz). That is, the sampling rate in the displacement measurement is 13/2 times the modulation frequency 2. Therefore, when the data of sampling number 1 (SP1) is obtained in phase 1 with the arrangement of the phase numbers shown in <A>, the data of sampling number 2 (SP2) is obtained in phase 3, and then <B> As shown, when data is obtained in the order of phase 5, phase 7, phase 9,... And data of sampling number 7 (SP7) is obtained in phase 13, sampling number 8 (in phase 2 of the next cycle) SP8) data is obtained. Further, as shown in <B>, data is obtained in the order of phase 4, phase 6, phase 8,..., And data of sampling number 13 (SP13) is obtained in phase 12. That is, as shown in <B>, by obtaining data from sampling numbers 1 to 13 (SP1 to SP13), data for one period from phase 1 to phase 13 (two periods on the waveform) is collected. The This situation is shown in FIG.

  Returning to FIG. 3, the modulation frequency 5 (192.30 Hz) is 5/13 of the frame rate (500 Hz). That is, the sampling rate in the displacement measurement is 13/5 times the modulation frequency 5. Accordingly, when the data of sampling number 1 (SP1) is obtained in phase 1 with the arrangement of the phase numbers shown in <A>, the data is obtained in order as shown in <B>, and sampling numbers 1 to 13 are obtained. By obtaining data from (SP1 to SP13), data for one period from phase 1 to phase 13 is collected.

  Similarly, at other modulation frequencies not illustrated in FIG. 3, data for sampling periods 1 to 13 (SP1 to SP13) is obtained, and data for one period from phase 1 to phase 13 is collected. be able to.

  According to the specific example of the modulation frequency setting shown in FIG. 3, it is possible to collect data with a relatively small number of samples (for example, 13) and no phase deviation, and it is possible to avoid the problem of aliasing. Note that, by collecting data without phase deviation, the RMS (Root Mean Squre) value becomes a value that does not greatly deviate from the RMS value when sampling is sufficiently fine.

  In this ultrasonic medical device, for example, the modulation frequency is determined by the above-described equation 1, and the displacement ultrasonic beam EB is modulated using the determined modulation frequency.

  FIG. 5 is a flowchart showing a specific example of the operation of the ultrasonic medical apparatus (the present ultrasonic medical apparatus) in FIG. First, a frame rate is set (S501). For example, when the depth of the diagnostic range is 15 cm, the time required for the reciprocation of ultrasonic waves is 15 (cm) × 2/1500 (m / s) = 100 μs (microseconds). For example, when the number of measurement ultrasonic beams MB is 20, the frame rate is 1 / (20 × 100 μs) = 500 Hz. Of the 20 measurement ultrasonic beams MB, for example, four measurement ultrasonic beams MB are used. For example, as shown in FIG. 2, when there are 20 measurement ultrasonic beams MB and four measurement ultrasonic beams MB are used for the measurement, the ratio of the time during which the temperature rises and the time during which the temperature falls Is 16: 4, and the rising time is four times the falling time, so that the temperature can be increased efficiently. (Actually, the above-mentioned increase / decrease ratio may not necessarily be obtained depending on the phase of the modulated wave, but the above relationship is generally established when the entire treatment time is viewed.)

  Next, a modulation frequency is set (S502). By making the modulation period sufficiently lower than the measurement period (see FIG. 2), the influence of the measurement period on the vibration can be reduced or avoided. For example, when the measurement period is 400 μs, it is necessary to make the modulation frequency sufficiently lower than 2.5 kHz. Further, in order to ensure time resolution on the order of seconds, it is desirable to repeat the vibration more than once per second, so that the modulation frequency is several Hz or more. While satisfying the above conditions, according to the specific example described with reference to FIG. 3, for example, the modulation frequency is set to 38.46 Hz, 76.92 Hz, or 192.30 Hz.

  Then, the tissue of the treatment site P is vibrated by the displacement ultrasonic beam EB based on the displacement ultrasonic wave transmission signal modulated at the modulation frequency, and the displacement measurement reception signal is transmitted via the measurement ultrasonic beam MB. Data is obtained (S503). For example, as described with reference to FIG. 3, data of sampling numbers 1 to 13 (SP1 to SP13) is collected in the time direction (period direction). Although only one set of data with sampling numbers 1 to 13 can be obtained for one period of the modulation frequency, for example, two sets of data are collected in order to reduce or eliminate the influence of noise and the like. Is done. Of course, two or more sets of data may be collected.

  When the received signal data for displacement measurement is obtained, the displacement measuring unit 24 measures the displacement based on the received signal data (S504). The displacement is measured for each sampling point (each depth), for example, for a plurality of sampling points arranged in the depth direction of the measurement ultrasonic beam MB. Further, for each sampling point, for example, adjacent data (n and n + 1, n = 1, 2,..., 25) in 26 points (26 time phases) of one data set are subjected to cross-correlation calculation or the like. And the displacement is calculated for each sampling point (each depth). For example, for 1024 sampling points arranged in the depth direction, the displacement is calculated for each sampling point, with the correlation window for correlation calculation being 64 sampling points. In addition, for example, the displacement may be calculated by comparing a time phase serving as a reference before the heat treatment and the latest time phase. Prior to the calculation of the displacement, a baseband removal process, a noise removal process, or the like may be performed as necessary.

  When the displacement is measured, the displacement map forming unit 25 forms a displacement map indicating a periodic change of the displacement based on the measured displacement (S505). Furthermore, the coagulation measuring unit 26 measures the coagulation of the tissue at the treatment site P based on the displacement map (S506).

  Then, intense focused ultrasound (HIFU) is irradiated to the treatment site P (S507). For example, the HIFU is irradiated for about 0.5 to 1.0 seconds by the therapeutic ultrasonic beam TB. Furthermore, if the heating period (see FIG. 2) has not ended (S508), the measurement processing from S503 to S506 is executed in the next measurement period (see FIG. 2), and HIFU is irradiated in S507 after the measurement period. The When the therapeutic ultrasonic beam TB is used as the displacement ultrasonic beam EB, the modulated HIFU is irradiated in S507, and the vibration components remaining after the HIFU irradiation are measured in S503 to S506.

  On the other hand, if the heating period (see FIG. 2) is completed (S508), the treatment at the treatment site P is completed. In the measurement of coagulation in S506, the treatment at the treatment site P may be terminated when the target coagulation size is confirmed. When the treatment at the treatment site P is completed, the treatment site P at another position may be treated.

  FIG. 6 is a diagram showing a specific example of the displacement map. The displacement map forming unit 25 forms, for example, a displacement map shown in FIG. 6 based on the displacement measured by the displacement measuring unit 24. FIG. 6 shows a displacement map in which the horizontal axis is time and the vertical axis is depth.

  In the vertical axis direction of FIG. 6, a plurality of sampling points (for example, 1024 sampling points) arranged in the depth direction of the measurement ultrasonic beam MB are arranged, and two sampling periods (each depth) are provided for two cycles. The displacements (two sets of sampling numbers SP1 to SP13 in FIG. 3) are arranged in the horizontal axis direction in FIG.

  Note that when the displacement map is formed, the displacements are rearranged in the time axis direction. For example, when 192.30 Hz (modulation frequency 5) described in FIG. 3 is used as the modulation frequency, the acquisition order of the sampling numbers SPn, that is, the order of SP1, SP2, SP3,. Therefore, as shown in FIG. 3, the sampling numbers SPn are rearranged in the time direction so as to correspond to the horizontal axis of FIG.

  In FIG. 6, for each sampling point in the depth direction, that is, for each depth, the magnitude of displacement (displacement amount) over two cycles in the time axis direction is mapped in correspondence with the magnitude of luminance. Has been. That is, in FIG. 6, a larger displacement in the positive direction is expressed brighter with higher luminance, and a larger displacement in the negative direction is expressed darker with lower luminance. Note that the magnitude of the displacement may be expressed by, for example, a color or the like instead of the luminance. A displacement map may be displayed on the display unit 50.

  In the specific example of FIG. 6, when the change in the displacement at the depth r indicated by the broken line is seen in the time axis direction, the displacement changes in a sine wave shape over two cycles. For example, when a modulated HIFU (modulated ultrasonic wave for displacement) is irradiated with the position at the depth r as a focal point, the tissue at the position at the depth r is displaced so as to follow the vibration of the HIFU. Then, a displacement map like the specific example shown in FIG. 6 is obtained.

  An effective vibration area may be set for the displacement map. For example, in the displacement map subjected to processing such as a median filter, an effective vibration region is a region where displacement exists for two cycles and the magnitude of the displacement is equal to or greater than a threshold value. In the measurement of coagulation described later based on the displacement map, for example, only data in the effective vibration region may be used. Thereby, the deterioration of the measurement accuracy accompanying the data outside the effective vibration region can be suppressed.

  As the tissue coagulation progresses due to irradiation with HIFU, a change appears in the displacement map. The coagulation measuring unit 26 measures tissue coagulation based on the displacement map.

  FIG. 7 is a diagram for explaining a change in the displacement map accompanying the progress of coagulation. FIG. 7A shows a specific example of a displacement map immediately after the start of HIFU irradiation. For example, the displacement map shown in FIG. 7A is obtained immediately after irradiating the HIFU whose beam length in the depth direction is HL (for example, the focal region is HL). In the region of the beam length HL (for example, the focal region), the tissue is displaced so as to follow the vibration of the HIFU.

  Further, in FIG. 7A immediately after the start of irradiation with HIFU, the tissue is not coagulated or the coagulation is small, and therefore, outside the region of the beam length HL, gradually deviates from the vibration of the HIFU as the distance from the beam length HL increases. The tissue is displaced. In other words, due to the vibration of the HIFU, a shear wave (shear wave) is generated in the region of the beam length HL, and the shear wave travels in the depth direction (toward the shallower and deeper directions), and shearing occurs in the displacement map. An inclination of displacement accompanying the wave propagation Sa appears.

  On the other hand, FIG. 7B shows a specific example of the displacement map after solidification. For example, if irradiation with the HIFU having the beam length HL shown in FIG. 7A is continued, solidification proceeds from the region of the beam length HL, and the tissue is solidified to the range of the solidified portion C shown in FIG. 7B, for example. In the coagulation portion C, the tissue is hard due to coagulation, and the shear wave propagates immediately. For example, as shown in FIG. 7B, the coagulation portion C is displaced so as to follow the vibration of the HIFU as a whole. In FIG. 7B, a displacement accompanying shear wave propagation Sb appears in an unsolidified portion.

  FIG. 8 is a diagram illustrating a measurement example of the solidification size Vs based on the displacement map. FIG. 8A shows a specific example of the displacement map. The coagulation measuring unit 26 performs frequency analysis of the displacement map in the time axis direction to extract a frequency component corresponding to the period of the modulation process for the displacement ultrasonic wave (HIFU), and coagulates the tissue based on the extracted frequency component. The size Vs is derived.

  FIG. 8B is a specific example of a processing result obtained by frequency analysis in the time axis direction with respect to the displacement map of FIG. The solidification measurement unit 26 performs FFT processing in the time axis direction for each sampling point for a plurality of sampling points arranged in the depth direction in the displacement map of FIG. 8A, and the processing result of FIG. Get.

  The vertical axis in FIG. 8 (b) corresponds to the same depth as in FIG. 8 (a), and the horizontal axis in FIG. 8 (b) indicates the frequency. And the brightness | luminance in FIG.8 (b) respond | corresponds to the absolute value after FFT processing.

  The coagulation measurement unit 26 extracts a frequency component (modulation frequency component) corresponding to the modulation frequency in the modulation processing of the displacement ultrasonic wave (HIFU) in the processing result of FIG. Then, the coagulation measurement unit 26 extracts the modulation frequency component at a plurality of sampling points arranged in the depth direction, and derives the coagulation size Vs of the tissue in the sampling direction based on the phase change in the sampling direction of the modulation frequency component. .

  FIG. 8C shows the phase of the modulation frequency component obtained by the FFT process. The horizontal axis in FIG. 8C corresponds to the depth direction, that is, the vertical axis in FIGS. 8A and 8B, and the vertical axis in FIG. 8C indicates the phase in radians.

  In the portion where the propagation speed of the shear wave is high, that is, the portion where the tissue is solidified, the tissue vibrates in substantially the same phase within the portion, and therefore the inclination of the phase waveform shown in FIG. On the other hand, in a portion where the propagation speed of the shear wave is slow, that is, a portion where the tissue is not solidified, the propagation of the shear wave takes time, so that a phase shift occurs for each place (for each depth), and FIG. The slope of the phase waveform shown in (c) increases.

  Therefore, the coagulation measurement unit 26 determines a portion having a small waveform inclination (for example, a portion having an inclination smaller than a threshold) in the waveform portion including the focal position of the HIFU based on the phase waveform shown in FIG. Is determined. Thereby, for example, as shown in FIG. 8C, a coagulation region including the focal position of the HIFU is determined, and a coagulation size Vs in the depth direction is derived.

  In the specific example shown in FIG. 8, since the FFT processing is performed, an improvement in the signal-to-noise ratio is expected. Further, in the specific example shown in FIG. 8, it is possible to evaluate the estimation accuracy of the unevenness of the solidified portion by using a statistical index or the like such as the standard deviation or variance of the data points constituting this section. Yes, the estimation accuracy may be used for comprehensive determination described in detail later.

  The coagulation measuring unit 26 calculates a displacement reduction rate for each sampling point in the depth direction based on the displacement map, and based on the displacement reduction rate for a plurality of sampling points, the tissue coagulation size Ar. May be measured.

  FIG. 9 is a diagram illustrating a measurement example of the solidification size Ar based on the displacement map. The flowchart in FIG. 9 is executed in parallel with, for example, irradiation of the intense focused ultrasound (HIFU) with respect to the treatment site P.

  First, a displacement map is formed at an initial diagnosis time (S901). For example, the initial diagnosis time is immediately before or after irradiation of the intense focused ultrasound (HIFU), and a displacement map (see FIG. 6) is formed.

  Further, a displacement map is formed at the next diagnosis time (S902). For example, the displacement map (see FIG. 6) is formed at the next diagnosis time after a certain time T has elapsed from the initial (one time before) diagnosis time.

  Then, it is confirmed whether or not the maximum displacement amount value in the displacement map at the diagnosis time in S902 is smaller than the maximum displacement amount value in the displacement map at the diagnosis time one hour earlier (S903). For example, the largest displacement in the effective vibration region (see FIG. 6) of the displacement map is set as the maximum displacement amount.

  If it is not smaller than the displacement amount maximum value of the displacement map at the diagnosis time one time ago, the process returns to S902, a displacement map is formed at the next diagnosis time, and the displacement amount maximum value is confirmed at S903. The processing in S902 and S903 is repeatedly executed until it becomes smaller than the maximum displacement amount of the displacement map at the diagnosis time one time ago.

  If it is confirmed in S903 that the displacement map is smaller than the maximum displacement amount at the diagnosis time one time ago, a displacement map serving as a reference is determined (S904). For example, the displacement map at the diagnosis time one time before confirmed in S903, that is, the displacement map at the time when the displacement reaches the peak is used as a reference. Note that, for example, a displacement map as a reference may be determined by averaging the displacement maps at the time when the displacement reaches the peak and the time before and after the time.

Depending on the initial temperature, tissue properties, etc. of the treated tissue, the maximum amount of displacement may increase and then decrease due to irradiation with HIFU (see Document 1 below). That is, there is not always a peak of the maximum displacement amount immediately before or after the irradiation of HIFU. According to the processing from S902 to S904, the displacement map at the time when the displacement maximum value reaches the peak is used as a reference even when the displacement maximum value increases and then decreases due to irradiation with HIFU. Can do.
Reference 1 “E Sapin-de Brosses, J Gennisson, M Pernot, M Fink and M Tanter,“ Temperature dependence of the shear modulus of soft tissues thermally by ultrasound. ”Phys Med Biol. 2010 Mar 21; 55 (6): 1701 -18 "(Document 1 describes the result of measuring the transverse elastic modulus when the temperature of the living tissue is changed. Depending on the living tissue, the temperature increases to a certain temperature as the temperature increases. The elastic modulus gradually decreases (the tissue becomes softer = the tissue displacement increases), and the transverse elastic modulus increases as the temperature increases from a certain temperature (the tissue becomes harder = the tissue displacement decreases). The result is shown in Document 1.)

  Then, a displacement map is formed at each diagnosis time over a plurality of diagnosis times (S905), and based on the displacement reduction rate obtained from the comparison between the displacement map at each diagnosis time and the reference displacement map, the treatment site The tissue coagulation size Ar in P is measured (S906). In the measurement of the solidification size Ar, the solidification measurement unit 26 desirably forms a displacement reduction rate map.

  FIG. 10 is a diagram illustrating a specific example of a displacement reduction rate map. The coagulation measurement unit 26 forms, for example, a displacement reduction rate map shown in FIG. FIG. 10 shows a displacement reduction rate map in which the HIFU irradiation time, that is, the diagnosis time, is set on the horizontal axis and the vertical axis is set on the depth. The depth of the vertical axis corresponds to the vertical axis of the displacement map (FIG. 6).

  The coagulation measuring unit 26 derives a displacement amount corresponding to the depth for each depth of the displacement map for the displacement map obtained at each diagnosis time. For example, in the displacement map obtained at each diagnosis time, the root mean square (RMS), that is, the effective value of the displacement is calculated from the change in displacement over two periods (horizontal axis in FIG. 6) for each depth. The effective value is defined as the displacement amount at the depth. Of course, the displacement amount of each depth may be determined by a calculation other than the root mean square.

  In addition, the solidification measuring unit 26 derives a displacement amount serving as a reference for each depth based on a displacement map serving as a reference. For example, the root mean square (RMS), that is, the effective value of the displacement is calculated from the change of the displacement over two periods (horizontal axis in FIG. 6) for each depth of the reference displacement map, and the effective value is calculated. The amount of reference displacement at that depth. Of course, the reference displacement amount at each depth may be determined by a calculation other than the root mean square.

  The coagulation measuring unit 26 calculates a ratio (Dm / Dr) between the displacement amount (Dm) obtained for each depth and the reference displacement amount (Dr) at the depth at each diagnosis time. Let the displacement decrease rate of that depth. Then, the displacement reduction rate is calculated for a plurality of depths over a plurality of diagnosis times, and the displacement reduction rate map of FIG. 10 is formed by mapping the luminance having a magnitude corresponding to the displacement reduction rate. Note that the displacement reduction rate may be expressed by, for example, a color or the like instead of the luminance. In addition, a displacement reduction rate map may be displayed on the display unit 50.

  The displacement reduction rate map of FIG. 10 is expressed brighter with higher brightness as the decrease from the reference displacement amount is smaller, that is, closer to the reference displacement amount, and as the decrease from the reference displacement amount is greater, that is, the reference displacement. The smaller the amount of displacement, the lower the brightness and the darker the expression. In the portion expressed dark in FIG. 10, it is expected that the tissue becomes hard due to the progress of coagulation and the amount of displacement decreases. That is, it is considered that the tissue is coagulated in the portion expressed darkly in FIG.

  An effective vibration region may be set for the displacement reduction rate map. For example, an effective vibration region (see FIG. 6) of the displacement map may be applied to the displacement reduction rate map, or a region where an effective reduction rate can be obtained by determining the effectiveness of the reduction rate in the displacement reduction rate map. May be the effective vibration region.

  The coagulation measuring unit 26 derives the coagulation size Ar in the tissue depth direction at each diagnosis time based on the displacement reduction rate map. For example, a portion having a small reduction rate (for example, a portion having a reduction rate smaller than the threshold) in the effective vibration region of the displacement reduction rate map shown in FIG. 10 is determined as the solidification region, and the length in the depth direction of the solidification region is solidified. Let it be size Ar.

  As described above, the coagulation measurement unit 26 derives the coagulation size Vs (see FIG. 8) and the coagulation size Ar (see FIG. 10) based on the displacement map. Furthermore, the coagulation measuring unit 26 calculates both the coagulation size Vs and the coagulation size Ar at each diagnosis time at a plurality of diagnosis times, and performs comprehensive determination based on the coagulation size Vs and the coagulation size Ar at each diagnosis time. The tissue coagulation size Coag may be determined. For example, using the weighting factors W1 and W2 (W1 + W2 = 1) for each of the coagulation size Vs and the coagulation size Ar, the total tissue coagulation size Coag is set to “Coag = W1 · Vs + W2 · Ar”.

  The weighting coefficients W1 and W2 may be changed as appropriate according to the conditions described below, for example, with a default value of W1 = W2 = 0.5.

<Condition 1> When measuring the solidification size smaller than the beam length in the depth direction of the HIFU The solidification size Vs is reliable unless the solidification size is larger than the beam length HL in the depth direction of the HIFU (FIG. 7). Since it is low, in the case of condition 1, the solidification size Ar is respected. For example, “Coag = Ar (W1 = 0, W2 = 1)”.

<Condition 2> When a site adjacent to a target site irradiated with HIFU has already solidified In the treatment using HIFU, HIFU is irradiated to a plurality of treatment sites P one after another in a region to be treated. If there is a coagulated site in the vicinity of the treatment site P, the signal-to-noise ratio may be lowered in deriving the rate of decrease in displacement at the treatment site P.

  FIG. 11 is a diagram illustrating a specific example of the treatment site P in the treatment region. In FIG. 11 (a), the site adjacent to the treatment site P scheduled to be irradiated with HIFU is already coagulated (coagulated site). For this reason, the coagulation size Vs is more respected than the coagulation size Ar obtained based on the decrease rate at the treatment site P. For example, “Coag = Vs (W1 = 1, W2 = 0)”.

  On the other hand, in FIG. 11B, since the treatment site P scheduled for HIFU irradiation is relatively far from the coagulation site, both the coagulation size Vs and the coagulation size Ar are used in the treatment site P. For example, “Coag = W1 · Vs + W2 · Ar (W1 + W2 = 1)”.

  The weighting factors W1 and W2 may be changed according to the distance L between the treatment site P and the coagulation site. For example, as the distance L is smaller, W2 is smaller than 0.5 and W1 is larger than 0.5. Also, the weighting factors W1 and W2 may be changed according to how many times the distance L is the beam width in the azimuth direction of the HIFU beam.

  Further, when HIFU is irradiated to a plurality of treatment sites P one after another, when the treatment site P adjacent to the coagulation site is always targeted, for example, in the irradiation to the first treatment site P, for example, “Coag = W1 · Vs + W2 · Ar (W1 + W2 = 1) ”may be used, and“ Coag = Vs (W1 = 1, W2 = 0) ”may always be used for irradiation of the second and subsequent treatment sites P.

<Condition 3> When the reliability of the solidification size Vs and the solidification size Ar can be evaluated When the reliability of the measurement result can be evaluated for at least one of the solidification size Vs and the solidification size Ar, weighting is performed according to the reliability. The coefficients W1 and W2 may be changed.

  For example, in the specific example described with reference to FIG. 8, the estimation accuracy of the coagulation size Vs is determined by using the statistical deviations such as the standard deviation or the variance of the data points constituting the interval. Since it is also possible to evaluate the weighting factors W1 and W2 may be set according to the estimation accuracy.

  In the specific example described with reference to FIG. 10, a portion with a small reduction rate (for example, a portion with a reduction rate smaller than a threshold) is determined as a solidified region, and the length in the depth direction of the solidified region is the solidified size. Although measured as Ar, the reliability of the solidification size Ar may be evaluated according to the degree of change in the reduction rate.

  FIG. 12 is a diagram for explaining the reliability of the solidification size Ar. FIG. 12 shows a specific example of the displacement reduction rate map. In other words, a displacement reduction rate map is shown in which the horizontal axis represents the time (diagnosis time) during which HIFU is irradiated and the vertical axis represents the depth. Specific examples of the displacement reduction rate at time T of this displacement reduction rate map are shown in FIGS. (A) and (b) show waveforms A and B with the horizontal axis representing depth and the vertical axis representing displacement reduction rate.

  In the waveform A, the change in the displacement reduction rate at the boundary between the solidified portion and the other portion is relatively steep. For example, the boundary can be detected with relatively high accuracy using a threshold value. Therefore, the reliability of the solidification size Ar measured based on the waveform A is high.

  On the other hand, in the waveform B, the change of the displacement reduction rate at the boundary between the solidified part and the other part is gentle, and the position of the boundary fluctuates relatively greatly depending on the threshold value, for example. For this reason, the coagulation size Ar measured based on the waveform B fluctuates relatively greatly depending on the threshold value, and the reliability is low.

  Therefore, the solidification measurement unit 26 determines the degree of change in the displacement reduction rate in the depth direction at the diagnosis time of the displacement reduction rate map, for example, depending on the steepness of the change in the vicinity of the boundary between the solidified part and the other part. The reliability of the size Ar may be evaluated, and the weighting factors W1 and W2 may be changed according to the reliability. For example, it is determined that the reliability of the solidification size Ar is higher as the change near the boundary is steeper, and the value of the weighting coefficient W2 is increased.

  In determining the coagulation size Coag of the tissue, the coagulation measurement unit 26 may determine the coagulation size Coag according to the treatment target.

  For example, when the treatment target is cancer, it is desirable to reliably coagulate necrosis of cancer cells (cancer tissue), and therefore, “Coag = Vs∩Ar”. That is, the product set (region belonging to both) of the range of the solidification size Vs and the range of the solidification size Ar is defined as the solidification size Coag. The smaller value of the solidification size Vs and the solidification size Ar may be set as the solidification size Coag. This makes it possible to reduce the survival of cancer cells and desirably eliminate the survival of cancer cells, thereby improving the safety and reliability of treatment.

  On the other hand, when the treatment target is a benign tumor such as uterine fibroid, it may be desirable to reduce the treatment area, unlike cancer. That is, the necessity of reliably leading to coagulation necrosis as in the case of cancer cells is low, and it is also conceivable to sparsely set irradiation points and irradiate HIFU. Therefore, when the treatment target is a benign tumor, for example, “Coag = Vs∪Ar” is set. That is, the sum of the range of the solidification size Vs and the range of the solidification size Ar (region belonging to at least one) is defined as the solidification size Coag. The larger value of the solidification size Vs and the solidification size Ar may be set as the solidification size Coag.

  As mentioned above, although preferred embodiment of this invention was described, embodiment mentioned above is only a mere illustration in all the points, and does not limit the scope of the present invention. The present invention includes various modifications without departing from the essence thereof. Needless to say, treatment using the ultrasonic medical device according to the present invention should be performed with sufficient care under the guidance of a specialist such as a doctor.

  DESCRIPTION OF SYMBOLS 10 Ultrasonic transducer, 20 Measurement diagnostic block, 22 Transmission / reception part, 24 Displacement measurement part, 25 Displacement map formation part, 26 Coagulation measurement part, 28 Ultrasound image formation part, 30 Treatment radiation block, 32 Treatment transmission part, 34 Displacement transmission unit, 36 modulation frequency control unit, 40 control unit, 50 display unit.

Claims (6)

A transmission unit that outputs a transmission signal of a displacement ultrasonic wave that periodically displaces the tissue;
A receiving unit for obtaining a reception signal of a measurement ultrasonic wave from a periodically displaced tissue;
A displacement measurement unit for measuring the displacement of the tissue based on the reception signal of the measurement ultrasonic wave;
Based on the measured displacement, a displacement processing unit for obtaining displacement data indicating a periodic change of the displacement,
A coagulation diagnostic unit for diagnosing tissue coagulation based on displacement data;
I have a,
The transmission unit outputs a transmission signal of the modulated displacement ultrasonic wave,
The displacement processing unit forms, as the displacement data, a displacement map showing a change in displacement along the time axis corresponding to the period of the modulation processing,
The coagulation diagnosis unit diagnoses coagulation of the tissue based on the displacement map;
An ultrasonic medical device. The ultrasonic medical device according to claim 1 ,
The displacement processing unit, for a plurality of sampling points arranged in the sampling direction, to form a displacement map showing a change in displacement at each sampling point,
The coagulation diagnostic unit derives a coagulation size in a tissue sampling direction based on the displacement map.
An ultrasonic medical device. The ultrasonic medical device according to claim 2 ,
The coagulation diagnosis unit extracts a frequency component corresponding to the period of the modulation process by performing frequency analysis of the displacement map in a time axis direction, and derives a tissue coagulation size Vs based on the extracted frequency component.
An ultrasonic medical device. The ultrasonic medical device according to claim 3 ,
The coagulation diagnosis unit derives a coagulation size Vs in a tissue sampling direction based on a phase change in the sampling direction of the frequency component extracted for a plurality of sampling points.
An ultrasonic medical device. The ultrasonic medical device according to any one of claims 2 to 4 ,
The coagulation diagnosis unit calculates a displacement reduction rate for each sampling point based on the displacement map obtained at each diagnosis time over a plurality of diagnosis times, and a displacement reduction rate for a plurality of sampling points. To derive the coagulation size Ar in the sampling direction of the tissue,
An ultrasonic medical device. The ultrasonic medical device according to any one of claims 2 to 5 ,
The coagulation diagnosis unit derives a tissue coagulation size Vs based on a frequency component corresponding to the modulation processing period obtained from the displacement map, and tissue coagulation based on a displacement reduction rate obtained from the displacement map. Deriving the size Ar and determining the coagulation size of the tissue by comprehensive determination based on the coagulation size Vs and the coagulation size Ar.
An ultrasonic medical device.