Acoustic coupler for HIFU treatment

Abstract

The purpose of the present invention is to clearly indicate whether or not a liquid container used in HIFU treatment is properly in contact with a patient. A HIFU irradiation system according to the present invention is provided with a coupling bag (14) serving as a liquid container positioned between the patient and each ultrasonic vibrator that transmits ultrasound for treatment, and a position adjusting part that determines the position of the coupling bag (14). On the outer surface of the coupling bag (14) facing the patient side, a first index line (50-1) to a third index line (50-3) indicating the state of contact with the patient are drawn.

Description

Acoustic coupler for HIFU treatment

[0001] The present invention relates to an acoustic coupler for HIFU therapy, and more particularly to a liquid container that is brought into contact with a patient during HIFU therapy.

[0002] A treatment device using high intensity focused ultrasound (HIFU) therapy is widely used. This treatment device is called a HIFU irradiation device or HIFU irradiation system, and irradiates a treatment site with ultrasound to cause tissue necrosis.

[0003] Generally, a HIFU irradiation device includes a plurality of ultrasonic transducers arranged on a bowl-shaped surface. The plurality of ultrasonic transducers are arranged so that ultrasonic waves emitted from each transducer are irradiated at a single point to form a focal point. During treatment, the focal point is aligned with the treatment area and ultrasonic waves are irradiated. To confirm the irradiation position, an ultrasonic diagnostic device that displays the focal point on an ultrasound image is used.

[0004] The following Patent Document 1 describes an ultrasonic treatment device that observes the position of a focal point using an ultrasonic diagnostic device that displays B-mode images (tomographic images). In this device, a therapeutic ultrasonic transducer emits ultrasonic waves at a low level that do not affect tissue, and an ultrasonic imaging probe transmits and receives ultrasonic waves to display a tomographic image. Since the acoustic properties of the subject's tissue change depending on the temperature of the tissue, the position of the focal point is indicated in the tomographic image by varying brightness.

[0005] Patent Documents 2 and 3 describe HIFU irradiation devices. In the HIFU irradiation device described in Patent Document 2, coupling bags are provided to hold liquid between an ultrasound transducer that emits therapeutic ultrasound and a patient, and between an ultrasound imaging probe and the patient. The coupling bags are filled with liquid. The coupling bags match acoustic impedances between the ultrasound transducer and the patient, and between the ultrasound imaging probe and the patient.

[0006] The HIFU irradiation device described in Patent Document 3 includes an ultrasonic therapy transducer and a coupling assembly configured to acoustically couple an ultrasonic imaging transducer to a patient. The coupling assembly is formed in a container shape with openings for receiving the ultrasonic therapy transducer and the ultrasonic imaging transducer, and the bottom side of the container shape contacts the patient. The coupling assembly is filled with a fluid that serves as an acoustic coupling medium for acoustically coupling the ultrasonic therapy transducer and the ultrasonic imaging transducer to the patient. By immersing the ultrasonic therapy transducer and the ultrasonic imaging transducer in the fluid filled in the coupling assembly, the ultrasonic therapy transducer and the ultrasonic imaging transducer are acoustically coupled to the patient.

[0007] Japanese Patent Laid-Open No. 8-71069 Japanese Patent Laid-Open No. 2023-104782 Special Publication No. 2023-530477

[0008] "Photonic Rubber: A nanotechnology material that changes color when deformed" Internet < https: / / trinus.jp / projects / 12?locale=ja >

[0009] In conventional technology, it can be difficult for a user to confirm whether a liquid container such as a coupling bag or a coupling assembly, which is placed between an ultrasonic transducer that emits therapeutic ultrasonic waves and a patient, is in proper contact with the patient.

[0010] An object of the present invention is to clearly indicate whether a fluid container used in HIFU Treatment is properly contacting a patient.

[0011] The acoustic coupler for HIFU treatment according to the present invention comprises a liquid container to be positioned between an ultrasonic transducer that transmits therapeutic ultrasonic waves and a patient, and a position adjustment unit that determines the position of the liquid container, and is characterized in that a contact indicator that indicates the state of contact with the patient is provided on the outer surface of the liquid container that faces the patient.

[0012] In one embodiment, the outer surface has a curved surface that bulges toward the patient, and the contact indicator indicates an indicator line that extends in a direction along the body surface of the patient.

[0013] In one embodiment, the outer surface is formed in an approximately circular shape when viewed from the patient's side, and the indicator line is part or all of a line that forms a circle or an approximately circular shape on a surface that follows the patient's body surface.

[0014] In one embodiment, the area forming the outer surface is formed of an elastic material, the outer surface has a curved surface that bulges toward the patient, the elastic material is a material that changes color when stretched, and the contact indicator is an indicator that changes color on the outer surface.

[0015] In one embodiment, the device includes a housing that fixes the ultrasonic vibrator, the liquid container includes a coupling bag that covers the housing and the ultrasonic vibrator from the patient side, the coupling bag holds liquid between the housing and the ultrasonic vibrator, and the position adjustment unit determines the position of the housing.

[0016] In one embodiment, the position adjustment unit adjusts the coupling distance between the housing and the ultrasonic transducer and the coupling bag, and multiple contact indicators are provided whose positions are determined according to differences in the coupling distance.

[0017] In one embodiment, an ultrasound imaging probe is attached to the housing, and the coupling bag covers the ultrasound imaging probe from the patient side.

[0018] In one embodiment, a housing for fixing the ultrasonic vibrator is provided, and the position adjustment unit determines the position of the liquid container separately from the position of the housing.

[0019] According to the present invention, it is possible to clearly indicate whether a liquid container used in HIFU treatment is in proper contact with a patient.

[0020] 1 is a diagram showing the configuration of a HIFU irradiation system according to a first embodiment; FIG. 1 is a diagram showing a HIFU transducer unit and a coupling bag; FIG. 1 is a diagram showing the coupling bag as viewed from below; FIG. 2 is a diagram showing the HIFU transducer unit, an adjustment mechanism, and a coupling bag, as well as the propagation region and focus through which therapeutic ultrasound propagates; FIG. 3 is a diagram showing the HIFU transducer unit, an adjustment mechanism, and a coupling bag, as well as the propagation region and focus through which therapeutic ultrasound propagates; FIG. 4 is a diagram showing the HIFU transducer unit, an adjustment mechanism, and a coupling bag, as well as the propagation region and focus through which therapeutic ultrasound propagates; FIG. 5 is a diagram showing the state of the coupling bag and the patient when the degree of contact between the coupling bag and the patient is insufficient; FIG. 6 is a diagram showing the state of the coupling bag and the patient when the degree of contact between the coupling bag and the patient is appropriate; FIG. 7 is a diagram showing the configuration of a HIFU irradiation system according to a second embodiment;

[0021] An embodiment of the present invention will be described with reference to the drawings. Identical components shown in multiple drawings will be assigned the same reference numerals, and their description will be omitted. Furthermore, terms such as up, down, left, and right in this specification indicate directions in the drawings. These directional terms are used for convenience of explanation and do not limit the orientation of each component when it is arranged.

[0022] Fig. 1 shows the configuration of a HIFU irradiation system 100 according to a first embodiment of the present invention. The HIFU irradiation system 100 includes an ultrasound imaging probe 10 (hereinafter referred to as the ultrasound probe 10), a HIFU transducer unit 12, a coupling bag 14, a robot arm 18, a controller 22, and a display device 24. In Fig. 1, a plane parallel to the surface on which a patient 30 lies is defined as the zx plane, and a coordinate axis perpendicular to the zx plane is defined as the y axis.

[0023] The HIFU transducer unit 12 includes a transducer housing 16 having a concave surface 4 with an opening facing downward, and a plurality of ultrasound transducers 2 arranged along the concave surface 4 of the transducer housing 16 and fixed to the transducer housing 16. The HIFU transducer unit 12 does not necessarily have to have an actual concave surface 4. In this case, the plurality of ultrasound transducers 2 may be fixed to the transducer housing 16 so as to be arranged along a virtual concave surface 4.

[0024] The concave surface 4 of the transducer housing 16 may have a shape similar to the side surface of a pyramid. Here, a pyramid refers to a three-dimensional shape formed by a collection of straight lines extending from a point in space to a bottom surface. The concave surface 4 of the transducer housing 16 may also have a dome-like shape bulging upward. Each ultrasonic transducer 2 is fixed to the transducer housing 16 so that when each ultrasonic transducer 2 emits ultrasound, the intensity of the ultrasound is increased at a treatment reference point P below the transducer housing 16. In other words, each ultrasonic transducer 2 is fixed to the transducer housing 16 so as to form a focal point F at the treatment reference point P.

[0025] The ultrasonic probe 10 is attached to the transducer housing 16 so that ultrasonic waves are transmitted and received at a position below the transducer housing 16 and above the focal point F. In this embodiment, the ultrasonic probe 10 passes through the apex of the transducer housing 16 in the vertical direction, and the probe tip 32 that transmits and receives ultrasonic waves faces downward. The ultrasonic probe 10 has directionality, and ultrasonic waves are transmitted and received on an observation surface that faces in a direction according to the structure of the ultrasonic probe 10. The ultrasonic probe 10 may be movable in the vertical direction. Furthermore, the ultrasonic probe 10 may be rotatable around a longitudinal axis.

[0026] Below the HIFU transducer unit 12, coupling bags 14 are provided to match the acoustic impedance between each ultrasound transducer 2 and the patient 30, and between the ultrasound probe 10 and the patient 30. The coupling bag 14 serving as a liquid container may be a bag filled with a liquid such as water. The coupling bag 14 may be made of an elastic material such as silicone resin. The coupling bag 14 holds the liquid between each ultrasound transducer 2 and the ultrasound probe 10 and the patient 30.

[0027] The ultrasound probe 10, the HIFU transducer unit 12, and the coupling bag 14 are attached to the tip of a robot arm 18 serving as a transport mechanism. The robot arm 18 is composed of a plurality of arms 18a connected by joints 18b, and is attached to the housing of a controller 22 via the joints 18b. Each arm 18a swings around the joint 18b as a rotation axis, whereby the robot arm 18 transports a movable body 20 including the ultrasound probe 10, the HIFU transducer unit 12, and the coupling bag 14 in three directions: the x-axis, the y-axis, and the z-axis.

[0028] The controller 22 includes a HIFU control unit 26 and a robot control unit 28. The HIFU control unit 26 includes a computer, an electric circuit for controlling the ultrasound probe 10, and an electric circuit for controlling the HIFU transducer unit 12. The computer included in the HIFU control unit 26 may be a business computer, a personal computer, a tablet computer, or the like. The computer executes a program to perform processes for generating each image and for displaying each image. An operating device (not shown) for a user to operate the HIFU irradiation system 100 is connected to the HIFU control unit 26. The operating device may include a mouse, a touch panel integrated with the display device 24, a switch, a keyboard, or the like.

[0029] The HIFU control unit 26 executes processing for operating the ultrasound probe 10 and the HIFU transducer unit 12. For example, the HIFU control unit 26 causes the ultrasound probe 10 to transmit and receive ultrasound, generates B-mode image data based on reception signals based on the ultrasound received by the ultrasound probe 10, and displays the B-mode image on the display device 24. The HIFU control unit 26 also causes each ultrasound transducer 2 included in the HIFU transducer unit 12 to transmit therapeutic ultrasound.

[0030] The robot control unit 28 may control the robot arm 18 in accordance with the control of the HIFU control unit 26, and cause the robot arm 18 to transport the movable body 20. The robot control unit 28 may also include an operating device. In this case, the robot control unit 28 may control the robot arm 18 in accordance with the operation of the operating device by the user.

[0031] Before the HIFU transducer unit 12 irradiates the patient 30 with therapeutic ultrasound, the following positioning process may be performed. The HIFU control unit 26 controls each ultrasound transducer 2 to transmit ultrasound waves with a lower intensity than that used during treatment. The position and orientation of the ultrasound probe 10 are set so that the observation plane of the ultrasound probe 10 coincides with the observation target plane of the patient 30. Here, the observation target plane refers to the plane on the patient 30 where an ultrasound image, such as a B-mode image, is observed. The HIFU control unit 26 causes the ultrasound probe 10 to scan the observation target plane of the patient 30 with an ultrasound beam to acquire B-mode image data. The HIFU control unit 26 controls the display device 24 to display the B-mode image. The user as a practitioner refers to the B-mode image displayed on the display device 24 to confirm the difference between the focus F of the ultrasound transmitted from the HIFU transducer unit 12 and the position of the affected area at the treatment reference point P.

[0032] If the difference between the position of the focal point F and the position of the affected area is not within an acceptable range, the user operates the robot arm 18 to change the position or posture of the ultrasound probe 10 and the HIFU transducer unit 12. After confirming that the position of the focal point F matches the position of the affected area, the user operates the HIFU control unit 26 for treatment. In response to the user's operation, the HIFU control unit 26 transmits therapeutic ultrasound having the intensity required for treatment to each ultrasound transducer 2. This cauterizes the living tissue at the focal point F, thereby providing treatment.

[0033] 2A shows an example of the HIFU transducer unit 12 and the coupling bag 14. FIG. 2B shows a view of the coupling bag 14 from below. The coupling bag 14 according to this embodiment has a curved surface that bulges toward the patient 30. When viewed from below, the shape of the coupling bag 14 is circular or approximately circular. In other words, the shape of the coupling bag 14 projected onto the zx plane is circular or approximately circular. Here, approximately circular refers to a shape that is a deformation of a circle to the extent that the function of the coupling bag 14 is not impaired.

[0034] On the outer surface of the coupling bag 14 facing the patient 30, first index lines 50-1 to third index lines 50-3 are drawn, in order from top to bottom, as contact indicators indicating the state of contact with the patient 30. The first index lines 50-1 to third index lines 50-3 are drawn in a plane along the body surface of the patient 30 by lines extending along the body surface of the patient 30. In the coupling bag 14 shown in FIGS. 2A and 2B, the first index lines 50-1 to third index lines 50-3 may be drawn so that their centers of gravity coincide with the center of gravity of the shape of the coupling bag 14 when projected onto the zx plane. If the shape of the coupling bag 14 projected onto the zx plane is circular, the first index lines 50-1 to third index lines 50-3 may be drawn as concentric circles with a common center at the center of the projected shape.

[0035] In the HIFU irradiation system 100 of this embodiment, an adjustment mechanism 52 for adjusting the distance between the HIFU transducer unit 12 and the coupling bag 14 is provided between the HIFU transducer unit 12 and the coupling bag 14. The distance between the HIFU transducer unit 12 and the coupling bag 14 (hereinafter referred to as the coupling distance) is defined as, for example, the difference in y-axis coordinate value between a predetermined reference point with respect to the transducer housing 16 and the lowest point of the coupling bag 14.

[0036] The adjustment mechanism 52 is controlled by the robot control unit 28, and the coupling bag 14 is movable in the vertical direction relative to the HIFU transducer unit 12. This allows the coupling distance to be adjusted according to the position of the focal point F. The coupling distance is adjusted in advance before treatment based on the depth of the focal point F from the body surface of the patient 30.

[0037] 3A to 3C show the HIFU transducer unit 12, adjustment mechanism 52, and coupling bag 14, as well as the propagation region 54 through which therapeutic ultrasound propagates and the focal point F, for three states with different coupling distances. Fig. 3B shows a case where the focal point F is located at a shallower position in the patient 30 than in Fig. 3A, and Fig. 3C shows a case where the focal point F is located at a shallower position in the patient 30 than in Fig. 3B. The position of the coupling bag 14 is adjusted so that the shallower the focal point F, the greater the coupling distance.

[0038] The first index line 50-1 to the third index line 50-3 are drawn at the outer edge of the propagation region 54 or at a position slightly outside the outer edge. That is, the first index line 50-1 is drawn at the outer edge of the propagation region 54 or at a position slightly outside the outer edge in the state shown in FIG. 3A where the coupling distance is smallest. The second index line 50-2 is drawn at the outer edge of the propagation region 54 or at a position slightly outside the outer edge in the state shown in FIG. 3B where the coupling distance is between the maximum and minimum values. The third index line 50-3 is drawn at the outer edge of the propagation region 54 or at a position slightly outside the outer edge in the state shown in FIG. 3C where the coupling distance is largest.

[0039] In the above example, the positions of the first index line 50-1 to the third index line 50-3 are determined based on the difference in the propagation region 54. Because the propagation region 54 differs depending on the difference in the coupling distance, the vertical positions of the first index line 50-1 to the third index line 50-3 may be determined depending on the difference in the coupling distance.

[0040] The use of the first index line 50-1 will be described below for the state shown in Figure 3A, where the coupling distance is smallest. Figure 4A shows the state of the coupling bag 14 and the patient 30 when the degree of contact between the coupling bag 14 and the patient 30 is insufficient. In this state, the first index line 50-1 drawn on the coupling bag 14 is visible to the user. In this state, a gap occurs between the coupling bag 14 and the patient 30 in the propagation region 54. In this case, the therapeutic ultrasound waves may be multiple-reflected in the gap between the coupling bag 14 and the patient 30, causing losses and reducing the energy delivered to the focal point F.

[0041] FIG. 4B shows the state of the coupling bag 14 and the patient 30 when the degree of contact between them is appropriate. The HIFU transducer unit 12 and the coupling bag 14 are moved downward under the control of the robot control unit 28, and the first index line 50-1 drawn on the coupling bag 14 is hidden by the body surface of the patient 30. In this state, the first index line 50-1 is not visible to the user. In this state, there is no gap between the coupling bag 14 and the patient 30 in the area where the therapeutic ultrasound is transmitted, and the degree of contact between the coupling bag 14 and the patient 30 is appropriate. Therefore, the appropriate state is the state when the HIFU transducer unit 12 and the coupling bag 14 are moved downward from the state shown in FIG. 4A until the first index line 50-1 drawn on the coupling bag 14 is hidden by the body surface of the patient 30 for the first time.

[0042] 3B, when the coupling distance is between the maximum and minimum values, the HIFU transducer unit 12 and the coupling bag 14 are moved downward, and the appropriate state is when the second index line 50-2 drawn on the coupling bag 14 is first hidden by the body surface of the patient 30. When the coupling distance is between the maximum and minimum values, as shown in FIG. 3C, when the HIFU transducer unit 12 and the coupling bag 14 are moved downward, and the appropriate state is when the third index line 50-3 drawn on the coupling bag 14 is first hidden by the body surface of the patient 30.

[0043] As described above, the HIFU irradiation system 100 according to this embodiment includes a HIFU therapy acoustic coupler including the coupling bag 14 as a liquid container positioned between the patient 30 and each ultrasonic transducer 2 that transmits therapeutic ultrasound, and the robot arm 18 as a position adjustment unit that determines the position of the coupling bag 14. Contact indices that indicate the contact state with the patient 30 are provided on the outer surface of the coupling bag 14 that faces the patient 30. The contact indices in this embodiment are the first index line 50-1 to the third index line 50-3 drawn on the coupling bag 14.

[0044] The HIFU therapy acoustic coupler allows the user to determine whether the contact state between the coupling bag 14 and the patient 30 is appropriate based on the contact index and the state of the patient 30. That is, whether the contact state between the coupling bag 14 and the patient 30 is appropriate can be determined based on whether the index line selected from the first index line 50-1 to the third index line 50-3 according to the coupling distance is hidden by the body surface of the patient 30.

[0045] Although the above example shows three index lines drawn on the coupling bag 14, any number of index lines may be drawn on the coupling bag 14. In other words, any number of index lines may be drawn on the coupling bag 14 depending on the possible values ​​of the coupling distance.

[0046] In the above example, the first index line 50-1 to the third index line 50-3, which are circular or nearly circular solid lines, are drawn on the coupling bag 14 as contact indicators indicating the contact state between the coupling bag 14 and the patient 30. Each index line may be drawn with a line that partially defines a section that is visible to the user. That is, the first index line 50-1 to the third index line 50-3 may be part or all of a line that forms a circle or nearly circle in a plane along the body surface of the patient 30.

[0047] Each index line may be represented by a boundary line between two regions of different colors. For example, on the outer surface of the coupling bag 14 facing the patient 30, the upper and lower regions of the first index line 50-1 may be represented by different colors, and the first index line 50-1 may be represented by a boundary line between the upper and lower regions.

[0048] The contact index may also be a circle, ellipse, polygon, or other mark arranged along a virtual index line, or a picture pattern arranged along a virtual index line.

[0049] At least a portion of the region of the coupling bag 14 that forms the outer surface facing the patient may be made of a stretchable material, and this material may be a material that changes color as it stretches. Examples of such stretchable color-changing materials include materials called photonic rubber (Non-Patent Document 1) and stretchable color sheets. The stretchable color-changing material functions as a contact indicator that indicates the contact state between the coupling bag 14 and the patient 30. For example, the outer surface of the coupling bag 14 facing the patient 30 may be provided with a band-like stretchable color-changing material that extends along a virtual indicator line. The user can determine whether the contact state between the coupling bag 14 and the patient 30 is appropriate based on the color of the stretchable color-changing material.

[0050] 5 shows the configuration of a HIFU irradiation system 102 according to a second embodiment of the present invention. In the HIFU irradiation system 102, the coupling bag 14 provided below the HIFU transducer unit 12 in the HIFU irradiation system 100 and the liquid therein have been removed. In place of the coupling bag 14, the HIFU irradiation system 102 is provided with a coupling container 64 as a liquid container and a position adjustment device 60 as a position adjustment unit that determines the position of the coupling container 64. A system such as the HIFU irradiation system 102 in which the coupling container 64 is separated from the HIFU transducer unit 12 is described in Patent Document 3.

[0051] The coupling container 64 has a container shape with an open top, and liquid is poured into the coupling container 64. The outer bottom surface of the coupling container 64, i.e., the outer surface on the patient 30 side, may have a curved surface that bulges outward toward the patient 30. The outer bottom surface of the coupling container 64 may be made of an elastic material.

[0052] The coupling container 64 is attached to a container position adjustment arm 62 included in the position adjustment device 60. The position adjustment device 60 is controlled by the robot control unit 28, and the position of the coupling container 64 is adjusted by the container position adjustment arm 62. During treatment, liquid is poured into the coupling container 64, and the bottom surface of the coupling container 64 is brought into contact with the patient 30. In this state, the robot arm 18 moves the movable body 20 downward, immersing the HIFU transducer unit 12 and the ultrasonic probe 10 in the liquid in the coupling container 64. As a result, the coupling container 64 is positioned between the HIFU transducer unit 12 including each ultrasonic transducer 2 and the patient 30, and the HIFU transducer unit 12 and the ultrasonic probe 10 are acoustically coupled to the patient 30 via the liquid in the coupling container 64.

[0053] As described above, in the HIFU irradiation system 102 according to this embodiment, the position adjustment device 60 serving as a position adjustment unit adjusts the position of the coupling container 64 serving as a liquid container separately from the position of the transducer housing 16 of the HIFU transducer unit 12.

[0054] Note that instead of the position adjustment device 60, a position adjustment unit that adjusts the position of the coupling container 64 without using power may be used. For example, the container position adjustment arm 62 may be configured to manually adjust the position of the coupling container 64. Alternatively, a stand including a columnar member that stands on the floor and an arm-like member extending laterally from the columnar member may be used as the position adjustment unit. In this case, the coupling container 64 is fixed to the tip of the arm-like member, and the length, height, etc. of the arm-like member are manually adjusted.

[0055] Similar to the coupling bag 14 in the HIFU irradiation system 100, the outer surface of the coupling container 64 facing the patient 30 side is provided with a contact indicator that indicates the contact state with the patient 30. The contact indicator may be the same as the indicator provided on the coupling bag 14. This allows the user to determine whether the contact state between the coupling container 64 and the patient 30 is appropriate based on the contact indicator and the state of the patient 30 when bringing the coupling container 64 into contact with the patient 30.

[0056] 2 Ultrasound transducer, 10 Ultrasound imaging probe (ultrasound probe), 12 HIFU transducer unit, 14 Coupling bag, 16 Transducer housing, 18 Robot arm, 18a Arm, 18b Joint, 20 Movable body, 22 Controller, 24 Display device, 26 HIFU control unit, 28 Robot control unit, 30 Patient, 50-1 First index line, 50-2 Second index line, 50-3 Third index line, 52 Adjustment mechanism, 54 Propagation area, 60 Position adjustment device, 62 Container position adjustment arm, 64 Coupling container, 100, 102 HIFU irradiation system.

Claims

1. An acoustic coupler for HIFU treatment comprising: a liquid container positioned between an ultrasonic transducer that transmits therapeutic ultrasonic waves and a patient; and a position adjustment unit that determines the position of said liquid container, wherein the outer surface of said liquid container that faces the patient is provided with a contact indicator that indicates the state of contact with said patient.

2. An acoustic coupler for HIFU therapy according to claim 1, wherein the outer surface has a curved surface that bulges out towards the patient, and the contact indicator indicates an indicator line that extends in a direction along the body surface of the patient.

3. An acoustic coupler for HIFU therapy according to claim 2, wherein the outer surface is formed in a substantially circular shape when viewed from the patient side, and the indicator line is a part or all of a line that describes a circle or a substantially circle on a surface that follows the surface of the patient's body.

4. An acoustic coupler for HIFU therapy as described in claim 1, wherein the area forming the outer surface is made of a stretchable material, the outer surface has a curved surface that bulges out towards the patient, the stretchable material is a material that changes color as it stretches, and the contact indicator is an indicator that changes color on the outer surface.

5. An acoustic coupler for HIFU therapy according to any one of claims 1 to 4, comprising a housing for fixing the ultrasonic vibrator, the liquid container comprising a coupling bag for covering the housing and the ultrasonic vibrator from the patient side, the coupling bag for holding liquid between the housing and the ultrasonic vibrator, and the position adjustment unit for determining the position of the housing.

6. An acoustic coupler for HIFU therapy according to claim 5, wherein the position adjustment unit adjusts the coupling distance between the housing and the ultrasonic vibrator and the coupling bag, and a plurality of contact indicators are provided whose positions are determined according to differences in the coupling distance.

7. An acoustic coupler for HIFU therapy according to claim 5, comprising an ultrasonic imaging probe attached to the housing, and the coupling bag covers the ultrasonic imaging probe from the patient side.

8. An acoustic coupler for HIFU therapy according to any one of claims 1 to 4, comprising a housing for fixing the ultrasonic vibrator, and wherein the position adjustment unit determines the position of the liquid container separately from the position of the housing.

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