JP5520150B2 - Ultrasonic measuring device and ultrasonic treatment system - Google Patents

Description

  The present invention relates to an ultrasonic measurement device and an ultrasonic therapy system that detect a temperature change in a living body.

  An ablation treatment apparatus for treating a living body by heating a malignant tumor or the like in the living body by using high intensity focused ultrasound (HIFU) or a radio wave has been put into practical use. In an ablation treatment apparatus, a treatment area including a malignant tumor or the like is heated to, for example, about 65 degrees Celsius. However, heating more than necessary, for example, heating of about 90 degrees Celsius or more is not preferable for a living body because there is a concern that the cell tissue is boiled. Therefore, in the treatment using the ablation treatment apparatus, it is desirable to heat the treatment region while checking the temperature of the treatment region.

  Against this background, several techniques using ultrasonic waves have been proposed in order to confirm the temperature in the living body. For example, Patent Documents 1 and 2 propose an apparatus for confirming the temperature of a tissue using ultrasonic waves. As a principle for confirming the temperature in the living body, Non-Patent Document 1 focuses on the temperature expansion of the tissue and changes the temperature based on the tissue expansion confirmed from the change in the distance between the two points. The principle of detecting is introduced. Furthermore, Non-Patent Document 2 introduces the temperature dependence of the sound velocity in the tissue.

Japanese Patent No. 2735280 JP-A-2005-530

Eunsol Baek and Jongbum Seo, “Temperature Estimation in HIFU with Lateral Speckle Tracking”, 2009 IEEE International Ultrasonics Symposium. U. Techavipoo et al, “Temperature dependence of ultrasonic propagation speed and attenuation in excised canine liver tissue measured using transmitted and reflected pulses”, J. Acoust. Soc. Am. 115 (6), June 2004, p2859-2865.

  In view of the background art described above, the inventor of the present application has repeatedly researched and developed an apparatus for detecting a temperature change in a living body using ultrasonic waves. In particular, we focused on the temperature dependence of the sound velocity in the tissue introduced in Non-Patent Document 2. Incidentally, the devices described in Patent Documents 1 and 2 do not focus on the temperature dependence of the sound speed.

  The present invention has been made in the process of research and development described above, and an object of the present invention is to provide an apparatus for detecting a temperature change in a living body based on the temperature dependence of sound speed.

  A suitable ultrasonic measurement apparatus that meets the above-described object includes a transducer that transmits and receives ultrasonic waves to and from a living body, a transmission and reception unit that obtains a reception signal from the living body by controlling transmission and reception of the transducer, A measurement point specifying unit for specifying a plurality of measurement points corresponding to different depths, and measuring a time interval between the plurality of measurement points in the received signal, and generating based on a change in the time interval. And a temperature change detection unit for detecting a temperature change in the body.

  In the ultrasonic measurement apparatus, the time interval between a plurality of measurement points corresponding to different depths is measured. When the temperature in the living body changes, the sound speed in the living body changes due to the temperature dependence of the sound speed. When the sound speed changes, the time interval between the plurality of measurement points also changes. Utilizing such a principle, the ultrasonic measurement apparatus detects a temperature change in the living body based on a change in a temporal interval between a plurality of measurement points.

  In a preferred embodiment, the ultrasonic measurement device generates the plurality of measurement points by changing tissue properties at different depths in the living body.

  In a desirable specific example, the ultrasonic measurement device changes the properties of the tissue at the plurality of locations by transmitting ultrasonic waves with a plurality of locations corresponding to different depths in the living body as focal points. A plurality of locations are defined as the plurality of measurement points.

  In addition, a suitable ultrasonic therapy system for the above purpose includes a treatment vibrator that heats the living body by transmitting relatively strong ultrasonic waves to the living body, and a transmission vibrator that controls transmission of the treatment vibrator. The therapeutic transmission unit which changes the properties of the tissue at the plurality of locations and uses the plurality of locations as a plurality of measurement points by transmitting ultrasonic waves with the plurality of locations corresponding to different depths as focal points. A measurement transducer that transmits and receives relatively weak ultrasonic waves to the living body, a measurement transmission / reception unit that controls transmission and reception of the measurement transducer to obtain a reception signal from the living body, and A measurement point specifying unit for specifying a measurement point and a time interval between a plurality of measurement points in the received signal are measured, and a temperature change in the living body accompanying the heating based on the change in the time interval Inspect And having a temperature change detection unit for, a.

  In a preferred embodiment, the ultrasonic treatment system includes a composite vibrator in which the treatment vibrator is disposed outside the measurement vibrator.

  In a preferred embodiment, the ultrasonic therapy system further includes a heating time control unit that controls an additional time of the heating based on the detected temperature change.

  According to the present invention, there is provided an apparatus for detecting a temperature change in a living body based on the temperature dependence of sound velocity.

It is a figure for demonstrating the transmission / reception control of a suitable ultrasonic wave in this invention. It is a figure for demonstrating the measurement of the time interval between measurement points. It is a figure which shows the suitable ultrasonic treatment system in implementation of this invention. It is a flowchart for demonstrating irradiation control of a powerful ultrasonic wave.

  Hereinafter, preferred embodiments of the present invention will be described.

  FIG. 1 is a diagram for explaining ultrasonic transmission / reception control suitable for the present invention. The composite vibrator 10 includes a measurement vibrator 12 and a treatment vibrator 14. The measurement vibrator 12 includes a plurality of vibration elements that transmit and receive ultrasonic waves. The plurality of vibration elements are controlled, an ultrasonic transmission beam is formed on the living body, and a reception signal is obtained along the reception beam. For example, an ultrasonic transducer provided in a known ultrasonic diagnostic apparatus may be used as the measurement transducer 12.

  On the other hand, the therapeutic transducer 14 includes a plurality of vibration elements that transmit relatively strong ultrasonic waves. The plurality of vibration elements are controlled to form a relatively strong therapeutic transmission beam for the living body. The therapeutic transducer 14 is disposed outside the measurement transducer 12. Further, the plurality of vibration elements constituting the treatment vibrator 14 are arranged so as to protrude in the depth direction toward the outer side, for example. As the treatment vibrator 14, for example, an ultrasonic vibrator provided in a cautery treatment apparatus that transmits a known high intensity focused ultrasound (HIFU) may be used.

  The measurement vibrator 12 and the treatment vibrator 14 may be configured by a plurality of vibration elements arranged one-dimensionally or may be formed by a plurality of vibration elements arranged two-dimensionally. In the case of a plurality of vibration elements arranged two-dimensionally, for example, the transducer surface of the measurement transducer 12 and the transducer surface of the treatment transducer 14 are formed concentrically, and the center of the concentric circle is formed. A circular measurement transducer 12 is disposed on the substrate, and an annular treatment transducer 14 is provided so as to surround it.

  The therapeutic transducer 14 transmits relatively strong ultrasonic waves targeting the treatment region 100 in the living body. For example, a transmission beam is formed so as to focus on the center position of the treatment region 100 including the malignant tumor and the like, and the treatment region 100 is heated by relatively strong ultrasonic waves to cauterize the malignant tumor and the like. For example, the treatment region 100 has a size of about 10 mm in the depth direction and about 5 mm in the lateral direction perpendicular to the depth direction. In this cauterization, the treatment area 100 is heated to, for example, about 65 degrees Celsius. However, heating more than necessary, for example, heating of about 90 degrees Celsius or more is not preferable because the cell tissue is boiled. Therefore, in the present embodiment, the temperature change of the treatment region 100 is confirmed using ultrasonic waves. In confirming the temperature change, a plurality of measurement points P1 and P2 are used.

  The plurality of measurement points P1 and P2 are in the treatment region 100 or in the vicinity of the treatment region 100, and are used for echo tracking processing described later. Therefore, it is desirable that each of the plurality of measurement points P1 and P2 is a reflected spot with a stronger ultrasonic wave than the surrounding tissue. In the present embodiment, a plurality of measurement points P1 and P2 are formed in the living body using the treatment vibrator 14.

  That is, the therapeutic transducer 14 forms a relatively strong ultrasonic transmission beam B1 with the location to be the measurement point P1 as a focal point. The transmission beam B1 changes the property of the tissue at the focal point, thereby measuring the measurement point P1. Is formed. By adjusting the direction of the transmission beam B1 and the position (depth) of the focal point by controlling the plurality of vibration elements included in the therapeutic transducer 14, the measurement point P1 can be placed at an arbitrary position within the control range. Can be formed. For example, a B-mode image including the treatment region 100 may be formed using the measurement transducer 12, and a user such as a doctor may confirm the B-mode image and determine the position of the measurement point P1. .

  Similarly, a relatively strong ultrasonic transmission beam B2 is formed by the therapeutic transducer 14 with the location to be the measurement point P2 as a focal point, and the tissue characteristics at the focal point are changed by the transmission beam B2, thereby measuring the measurement point. P2 is formed. The measurement point P1 and the measurement point P2 are formed at different depths.

  When the measurement point P1 and the measurement point P2 are formed using the treatment vibrator 14, the time interval between the measurement points P1 and P2 is measured using the measurement vibrator 12. In this measurement, a known echo tracking process is used. For example, if there is a relatively hard tissue suitable for echo tracking processing in the treatment region 100 or in the vicinity of the treatment region 100, the existing tissue is used as a plurality of measurement points P1 and P2. Also good.

  FIG. 2 is a diagram for explaining measurement of a time interval between measurement points. In this measurement, the measurement transducer 12 (FIG. 1) is used, and measurement ultrasonic beams (transmission beam and reception beam) are formed at the measurement point P1 and the measurement point P2, and the ultrasonic beam. A received signal is obtained along Since the measurement points P1 and P2 are relatively strong reflected spots of ultrasonic waves, the amplitude of the signal portion corresponding to the measurement points P1 and P2 is relatively large in the received signal. FIG. 2 shows a received signal including signal portions corresponding to the measurement points P1 and P2.

  FIG. 2 (I) shows the received signal before the temperature change, and FIG. 2 (II) shows the received signal after the temperature change. In the received signal obtained from the ultrasonic beam formed so as to pass through the measurement point P1, the amplitude of the signal portion corresponding to the measurement point P1 is relatively large. Further, in the reception signal obtained from the ultrasonic beam formed so as to pass through the measurement point P2, the amplitude of the signal portion corresponding to the measurement point P2 is relatively large. The signal portion corresponding to the measurement point P1 and the signal portion corresponding to the measurement point P2 may be specified by one ultrasonic beam passing through the two measurement points P1 and P2.

  When the signal portion is simply regarded as a portion having a large amplitude, the signal portion spreads in the time axis direction (depth direction), and therefore an error may occur depending on the extent of the spread. Therefore, in this embodiment, for example, an echo tracking process detailed in Japanese Patent Laid-Open No. 2001-309918 is used.

  In the echo tracking process, a zero cross point is detected as a representative point of the signal portion, and the extraction accuracy is dramatically improved by tracking the detected zero cross point. The zero-cross point is detected as a timing at which the polarity of the echo signal (reception signal) is reversed from positive to negative or from negative to positive within the tracking gate period set as the tracking range. When a zero cross point is detected, a tracking gate is newly set around that point. And in the echo signal acquired from the same site | part at the next transmission / reception timing, a zero crossing point is detected within the newly set tracking gate period.

  In this way, the zero cross point Z1 of the signal portion corresponding to the measurement point P1 is tracked by the echo tracking process as shown in FIG. Similarly, the zero cross point Z2 of the signal portion corresponding to the measurement point P2 is also tracked. Then, the time interval between the zero cross point Z1 and the zero cross point Z2 is measured. This time interval corresponds to the propagation time of the ultrasonic wave between the zero cross point Z1 and the zero cross point Z2.

  In the present embodiment, attention is paid to the temperature dependence of the sound speed in a living body. For example, when there is no change in the distance between the measurement points P1 and P2 and the sound speed increases due to a temperature change in the living body, the propagation time of the ultrasonic wave between the measurement points P1 and P2 is shortened. In this case, the time interval Ta after the temperature change shown in FIG. 2 (II) is smaller than the time interval Tb before the temperature change shown in FIG. 2 (I). Therefore, the temperature change can be detected from the change in the time interval between the measurement points.

  For example, if the received signal (echo signal) is sampled at 400 MHz in the echo tracking process, a resolution of about 3 degrees is obtained in terms of phase. In addition, when the temperature dependence of the sound speed of a general tissue is set to a sound speed change of 0.6 m / s per degree, and further, an ultrasonic frequency is 6 MHz, a path length is 1 cm, and a sound speed is 1500 m / s, The temperature detection sensitivity Δt by the echo tracking process is 0.26 degrees as shown in the following equation. In the following equation, ΔL is the amount of change in path length per temperature of 1 degree, and D is the path length detection accuracy.

  In addition, although the expansion | swelling of the biological tissue with a temperature rise is known (refer nonpatent literature 1), the expansion | swelling is about 0.36 micrometer per temperature, and will be 0.03 m / s when converted into a sound speed. . This is extremely small compared with the above-described temperature dependence of the sound speed of 0.6 m / s, and is negligible. Of course, correction processing considering the influence of expansion may be added.

  FIG. 3 is a diagram showing an ultrasonic treatment system suitable for carrying out the present invention. The therapeutic transducer 14 transmits a relatively strong ultrasonic wave, heats the treatment region, and is also used to form a measurement point (see FIG. 1). The transmission of the therapeutic transducer 14 is controlled by the transmission unit 24.

  The measurement transducer 12 is controlled by the transmission / reception unit 22 and electronically scans an ultrasonic beam in a two-dimensional plane including a treatment region in a living body or in a three-dimensional space. The plurality of ultrasonic beams are electronically scanned one after another, and an echo signal (reception signal) is acquired for each ultrasonic beam. The acquired plurality of echo signals are output to the image forming unit 42, and the image forming unit 42 forms an in-vivo ultrasonic image (such as a B-mode image or a three-dimensional image) based on the plurality of echo signals. The formed ultrasonic image is displayed on the display unit 44.

  The echo signal acquired by the transmission / reception unit 22 is also output to the echo tracking processing unit (ET processing unit) 32. The echo tracking processing unit 32 performs the echo tracking processing described with reference to FIG. The tracking echo signal used for the echo tracking process may be selected from a plurality of ultrasonic beams used for the ultrasonic image, or separately from the ultrasonic beam for the ultrasonic image. A tracking echo signal may be obtained by forming an ultrasonic beam for use.

  The temperature change detection unit 34 detects a temperature change in the treatment region accompanying heating from the change in the time interval between the measurement points measured by the echo tracking process described with reference to FIG. That is, the temperature change detection unit 34 confirms the change in sound speed from the change in the time interval (Tb, Ta) shown in FIG. 2, and detects the change in temperature. The detection result is displayed on the display unit 44, for example.

  The detection result of the temperature change by the temperature change detection unit 34 is transmitted to the control unit 50, and the control unit 50 controls the transmission unit 24 based on the detected temperature change. The control unit 50 controls the irradiation time of the strong ultrasonic waves by the transmission unit 24 based on the detection result of the temperature change.

  For example, according to the measurement result of the sound speed relating to the dog's liver (FIG. 2 of Non-Patent Document 2), the sound speed peak is about 60 degrees Celsius. That is, in the range from about 20 degrees Celsius to about 60 degrees Celsius, the sound speed increases as the temperature increases, and in the range from about 60 degrees Celsius to about 90 degrees Celsius, the sound speed decreases as the temperature increases. A similar phenomenon is observed in sound speed in water, and the sound speed peak is about 75 degrees Celsius. The main component of biological tissue is water, and considering the measurement results regarding the dog's liver, it is expected that the peak of sound velocity will appear in the biological tissue in the range of about 60 degrees Celsius to about 75 degrees Celsius. Is done. That is, by detecting the peak of the speed of sound, for example, it can be confirmed that the living tissue is at a temperature of about 60 degrees Celsius to about 75 degrees Celsius. Therefore, for example, the control unit 50 determines the peak of the sound velocity from the detection result of the temperature change, determines that the living tissue is, for example, about 60 degrees Celsius to about 75 degrees Celsius, and stops the irradiation of high intensity ultrasound. Alternatively, the remaining time for irradiating the powerful ultrasonic wave is determined.

  FIG. 4 is a flowchart for explaining irradiation control of intense ultrasonic waves by the ultrasonic therapy system of FIG. The irradiation control will be described according to the flowchart of FIG. 4 using the reference numerals shown in FIGS.

  First, an ultrasonic image in the living body is formed by using the measurement transducer 12, and a user such as a doctor confirms the position and size of the treatment region 100 with reference to the ultrasonic image (S401, S401). (See FIG. 1). Then, the treatment transducer 14 is used to set a plurality of measurement points P1 and P2 (S402, see FIG. 1). Further, the time interval Tb between the measurement points P1 and P2 is measured by echo tracking processing using the measurement transducer 12 (S403, see FIG. 2).

  Next, the treatment transducer 14 is used to irradiate the treatment region 100 with intense ultrasonic waves (S404). Then, when a strong ultrasonic wave is irradiated for a predetermined number of seconds, for example, the high intensity ultrasonic wave is stopped and the irradiation time is integrated (S405). Thereafter, the time interval Ta between the measurement points P1 and P2 is measured by echo tracking processing using the measurement transducer 12 (see S406, FIG. 2), and the time interval measured before the irradiation with the powerful ultrasonic wave is performed. The time interval Ta measured after the irradiation with Tb and the powerful ultrasonic wave is compared (S407).

  In the comparison in S407, if the time interval Ta after irradiation is equal to or less than the time interval Tb before irradiation, it is determined that the sound velocity tends to increase and the temperature of the treatment region 100 tends to increase, and high-power ultrasound is irradiated again. The processing from S404 to S407 is executed. In step S407, the time interval Ta after irradiation is compared with the previous time interval Ta. If the time interval Ta after irradiation is equal to or less than the previous time interval Ta, the processing from S404 to S407 is further performed. Executed.

  When the processing from S404 to S407 is repeated, that is, when irradiation with high intensity ultrasound is repeatedly performed, the temperature of the treatment region 100 continues to rise. For example, the sound speed peaks at about 60 degrees Celsius to about 75 degrees Celsius. . When the sound velocity tends to decrease beyond the peak, the time interval Ta after irradiation becomes larger than the previous time interval Ta in the comparison of S407.

  Thus, when it is confirmed in S407 that the sound velocity has exceeded the peak and it is determined that the temperature of the treatment region 100 has reached, for example, about 60 degrees Celsius to about 75 degrees Celsius, an additional irradiation time is determined (S408). ). For example, an additional irradiation time based on experimental data or the like is determined so that the temperature of the treatment region 100 becomes a desired temperature without reaching 90 degrees Celsius. Then, the intense ultrasonic wave is further irradiated to the treatment region 100 for the additional irradiation time (S409).

  According to the irradiation control shown in FIG. 4, after confirming that the temperature of the treatment region 100 has reached, for example, about 60 degrees Celsius to about 75 degrees Celsius, an additional irradiation time at which the desired temperature is reached is determined. Therefore, the irradiation time can be controlled with relatively high accuracy, for example, excessive heating can be suppressed.

  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.

  DESCRIPTION OF SYMBOLS 10 Composite type | mold vibrator, 12 Measurement vibrator | oscillator, 14 Treatment vibrator | oscillator, 32 Echo tracking process part, 34 Temperature change detection part, 50 Control part.

Claims (6)

A vibrator for transmitting and receiving ultrasonic waves to a living body;
A transmission / reception unit that obtains a reception signal from the living body by controlling transmission / reception of the vibrator;
A measurement point specifying unit for specifying a plurality of measurement points corresponding to different depths in the received signal;
A temperature change detection unit that measures a time interval between a plurality of measurement points in the received signal, and detects a temperature change in the living body based on a change in the time interval;
A control unit that determines whether or not the living body in which the temperature change has been detected has reached a temperature at which the sound speed of the ultrasonic wave reaches a peak; and
Having
An ultrasonic measurement device characterized by that. The ultrasonic measurement apparatus according to claim 1,
Irradiation of strong ultrasonic waves to the living body is repeated a plurality of times,
Whether the control unit tends to increase or decrease the speed of sound based on the time interval before irradiation and the time interval after irradiation for each of the plurality of times of irradiation. Determining that the sound speed has reached a temperature at which the sound speed reaches a peak, with the sound speed changing from an increasing tendency to a decreasing tendency in the determination over a plurality of times.
An ultrasonic measurement device characterized by that. The ultrasonic measurement apparatus according to claim 2,
If the time interval after irradiation is equal to or less than the time interval before irradiation, the control unit tends to increase the speed of sound, and the time interval after irradiation is the time interval before irradiation. If it is larger than that, it is determined that the sound speed tends to decrease.
An ultrasonic measurement device characterized by that. A treatment vibrator that heats the living body by transmitting relatively strong ultrasonic waves to the living body;
By transmitting the ultrasonic wave with a plurality of locations corresponding to different depths in the living body being controlled by transmitting the treatment vibrator, the tissue properties at the plurality of locations are changed to change the plurality of locations. A transmitter for treatment with a plurality of measurement points,
A measurement transducer that transmits and receives relatively weak ultrasonic waves to a living body;
A transmission / reception unit for measurement to obtain a reception signal from the living body by performing transmission / reception control of the measurement vibrator;
A measurement point specifying unit for specifying the plurality of measurement points in the received signal;
A temperature change detecting unit that measures a time interval between a plurality of measurement points in the received signal and detects a temperature change in the living body due to the heating based on a change in the time interval;
A control unit that determines whether or not the living body in which the temperature change has been detected has reached a temperature at which the sound speed of the ultrasonic wave reaches a peak; and
Having
An ultrasonic therapy system characterized by that. The ultrasonic therapy system according to claim 4, wherein
Having a composite vibrator in which the treatment vibrator is arranged outside the measurement vibrator;
An ultrasonic therapy system characterized by that. The ultrasonic therapy system according to claim 4 or 5,
The therapeutic vibrator repeatedly irradiates a relatively strong ultrasonic wave multiple times,
Whether the control unit tends to increase or decrease the speed of sound based on the time interval before irradiation and the time interval after irradiation for each of the plurality of times of irradiation. Determining that the sound speed has reached a temperature at which the sound speed reaches a peak, with the sound speed changing from an increasing tendency to a decreasing tendency in the determination over a plurality of times.
An ultrasonic therapy system characterized by that.

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