JP2017169865A - Fat diagnostic ultrasound probe - Google Patents

Abstract

The present invention provides an ultrasonic probe for fat diagnosis capable of irradiating ultrasonic waves from a main probe and ultrasonic waves from a sub-probe in a coaxial manner without using a drive mechanism. A probe holder 5 is inclined so that an ultrasonic wave signal from a main probe 2 is incident obliquely on an axis L through which a propagation body 3 passes straight, and is emitted from a sub-probe 4. The flat plate member 5a for reflecting the irradiated ultrasonic energy and irradiating it in the extending direction of the axis L is fixed. The flat plate member 5a has a propagation characteristic of Lamb wave A0 mode in the flat plate member 5a. The propagation condition of the Lamb wave A0 mode is set in accordance with the frequency of the ultrasonic signal and the material of the propagating body 3 so that it can pass through the flat plate member 5a and propagate in the direction of extension of the axis L. The inclination angle, material, and thickness of the flat plate member 5a with respect to the axis L to be filled are set. [Selection] Figure 1

Description

  The present invention relates to an ultrasonic probe for fat diagnosis used in fat diagnosis based on an ultrasonic velocity change. The present invention is used, for example, in the diagnosis of fatty liver and the diagnosis of lipidity in intravascular plaque.

  As a new fat diagnostic method, the change in ultrasonic velocity before and after heating is measured, the part where the ultrasonic velocity changes negatively with respect to the temperature change is detected as adipose tissue, and the fat tissue detection method diagnoses fat distribution And a detection device is proposed (refer to patent documents 1).

  A fat diagnostic apparatus (adipose tissue detection apparatus) described in Patent Document 1 will be described. This device is based on a reflection-type ultrasonic diagnostic device capable of acquiring a B-mode tomographic image, and has a device main body additionally equipped with a control unit necessary for acquiring an ultrasonic velocity change image and a body surface of a subject. And a probe for direct ultrasonic contact and heating. The probe used here includes an array-type multi-channel probe (linear array probe) that irradiates ultrasonic waves for diagnostic imaging to the measurement region of the subject, and the multi-channel probe is adjacent to the subject. In order to heat the measurement region of the specimen, a dedicated probe in which an infrared laser light source that irradiates near infrared light is arranged side by side is used.

  The multi-channel probe has a large number of transducers composed of linearly arranged piezoelectric elements, and each transducer transmits an ultrasonic signal with a pulse wave excited by a drive signal from a control unit. The ultrasonic echo signal from the inside of the subject with respect to the ultrasonic signal is received. Then, scanning is performed by sequentially switching transducers that perform transmission and reception according to a control signal. The infrared laser light source emits 700 nm to 1000 nm of near infrared light from the side of the multichannel probe.

Next, the operation of measuring the ultrasonic velocity change with this apparatus and performing a fat diagnosis will be described. A measurement region in the subject is specified in advance by image diagnosis using a B-mode image acquired by driving the multi-channel probe. The specified measurement area is heated by irradiating near infrared light from an infrared laser light source, and after a predetermined heating time has elapsed, the linear array probe is driven to sequentially scan pulsed ultrasonic signals. In this manner, the ultrasonic waves are transmitted sequentially, and ultrasonic echo signals that are received signals from the subject are sequentially received. And the waveform of the ultrasonic echo signal (reception signal) received in the light irradiation state is stored as an ultrasonic echo signal after light irradiation.
After storing the received waveform of the ultrasonic echo signal after the light irradiation, the light irradiation is stopped. When a predetermined time elapses after the irradiation is stopped and the temperature of the subject is sufficiently lowered, the linear array probe is driven again to transmit an ultrasonic signal and receive an ultrasonic echo signal from the subject. . And the waveform of the ultrasonic echo signal (reception signal) received in the light irradiation stop state is stored as a non-irradiation ultrasonic echo signal. The stored ultrasonic echo signal is displayed as a B-mode tomographic image by displaying its amplitude in luminance.
Subsequently, the ultrasonic velocity change is obtained from the relationship shown below based on the ultrasonic echo signals after the light irradiation and at the time of non-irradiation.

FIG. 9 is a schematic diagram showing an ultrasonic echo signal before heating (during normal temperature) and an ultrasonic echo signal after heating (during temperature increase) in a certain partial section. The ultrasonic velocity before heating is V, and the ultrasonic velocity after heating is V ′. Also, let τ be the pulse interval that occurs when the ultrasonic signal propagates between the boundaries before heating, and let τ ′ be the pulse interval that occurs when the ultrasonic signal propagates after light irradiation between the same boundaries (constant distance) = Τ + Δτ. In other words, it is assumed that the pulse interval is shifted by Δτ due to a temperature change so as to become longer.
At this time,
V · τ = V '· (τ + Δτ) (1)
Therefore, the ultrasonic velocity change data can be calculated by the following equation (2) from the time change of the pulse interval between the two ultrasonic echo signals.
V ′ / V = τ / (τ + Δτ) (2)
Therefore, the pulse interval (τ) and the waveform shift amount (Δτ) in the region of interest are calculated from the two measured ultrasonic echo signals, and the change in the ultrasonic velocity (ultrasonic velocity) at each part is calculated based on the equation (2). Change ratio (V ′ / V)) is calculated.

Subsequently, based on the calculated ultrasonic velocity change ratio (V ′ / V) of each region, a region where this value is smaller than 1 (region where the ultrasonic velocity change with respect to heating is negative) is determined as a fat region. .
That is, the ultrasonic velocity propagating in water and fat is 1524 m / sec in water and 1412 m / sec in fat when the temperature is 37 ° C. When the ultrasonic velocity change with respect to temperature change is compared, it is as follows. is there.
Water: +2 m / sec / ° C
Fat: -4 m / sec / ° C
Therefore, when the temperature rises in muscles and internal organs (liver etc.) that contain a lot of water, the ultrasonic velocity increases in the fat part, and the polarity of the ultrasonic velocity change is reversed. To do.
Therefore, a fat region can be detected by specifying a region where the ultrasonic velocity change is negative when the temperature of the measurement region is changed.

  Then, from the analysis result of the ultrasonic velocity change by the multiple ultrasonic echo signals received by scanning the array type probe, the two-dimensional distribution of the ultrasonic velocity change is imaged and displayed on the display device. The fat region is clearly displayed separately from other parts.

  A fat diagnostic apparatus using ultrasonic energy for heating has also been proposed. That is, a probe that emits an ultrasonic beam for heating is used as a heating source, and this is placed adjacent to the ultrasonic diagnostic probe, and the ultrasonic velocity change before and after heating is performed by heating with the ultrasonic beam. There has been proposed a blood vessel plaque image diagnosis apparatus that performs image diagnosis of lipid tissue of a blood vessel plaque by measuring (see Patent Document 2).

In addition, the main probe for diagnostic imaging and the auxiliary probe for heating are attached to the probe holder, and the traveling direction of the ultrasonic wave (signal) from the main probe and the traveling direction of the ultrasonic wave (energy) from the secondary probe are coaxial. There is disclosed a technique in which the direction is set (see Patent Document 3).
Specifically, as shown in FIG. 10, in the conventional ultrasonic diagnostic probe 100 for fat diagnosis, images are formed on the upper and side surfaces of a probe holder 101 filled with a propagation liquid (water, oil, etc.) through which ultrasonic waves propagate. A multi-channel main probe 102 for diagnosis and a sub probe 103 for heating are attached. Then, by switching the position of the switching mirror 104 provided in the probe holder 101, either the ultrasonic wave from the main probe 102 goes straight or the ultrasonic wave from the sub probe 103 is reflected by the switching mirror 104, either The object can be selectively irradiated from the emission port 105 (with a silicone rubber sheet attached as a window material). As a result, the measurement position (position in the center of the image) specified by the image diagnosis by the main probe 102 can be heated accurately and coaxially by the sub probe 103 and irradiated from the common exit port 105. It has been disclosed that ultrasonic heating can be safely performed even from a narrow width between ribs.

JP 2010-005271 A JP 2013-070704 A JP 2006-013176 A

  When the fat diagnostic ultrasonic probe described in Patent Document 3 is used, heating by ultrasonic waves can be performed by bringing the exit of the probe into contact with the gap between the ribs, and compared with light heating, Since even deep parts can be heated, for example, it is possible to diagnose fat in the liver located in the deep part of the living body from between the ribs.

  By the way, according to the ultrasonic diagnostic probe 100 for fat diagnosis shown in FIG. 10, when heating is performed by the sub probe 103, the switching mirror 104 is placed on the axis of the ultrasonic wave irradiated from the sub probe 103 (indicated by the dotted line in FIG. 10). Position). Further, when the ultrasonic echo signal is measured by the main probe 102, the switching mirror 104 needs to be moved to the retracted position (the position indicated by the solid line in FIG. 10). A driving mechanism for the mirror 104 is required and the structure is complicated.

Accordingly, an object of the present invention is to provide an ultrasonic probe for fat diagnosis that can irradiate ultrasonic waves from a main probe and ultrasonic waves from a sub probe in a coaxial manner without using a drive mechanism. .
In the following description, a diagnostic ultrasonic wave emitted from the main probe is referred to as an “ultrasonic signal”, and a heating ultrasonic wave irradiated from the sub probe is referred to as “ultrasonic energy”. The former is emitted as a pulse wave, and the latter is irradiated as a continuous wave.

  The ultrasonic diagnostic probe for fat diagnosis of the present invention, which has been made to solve the above-mentioned problems, has a main probe and a sub probe mounted on a probe holder, and a diagnostic ultrasonic signal emitted from the main probe and the sub probe The ultrasonic diagnostic ultrasound probe for heating is irradiated with ultrasonic energy for heating, which is emitted from the body and propagates through the propagation body filled in the probe holder, and the subject is irradiated with the ultrasonic probe. On the axis line through which the ultrasonic signal from the probe passes straight through the propagation body, the axis line is inclined so that the axis line is incident obliquely, and the ultrasonic energy emitted from the sub probe is reflected to the axis line. The flat plate member to be irradiated in the extending direction of the flat plate member is fixed. The flat plate member has a propagation characteristic of Lamb wave A0 mode in the flat plate member. Depending on the frequency of the ultrasonic signal and the material of the propagating body, the propagation condition of the Lamb wave A0 mode is set so that it can pass through the flat plate member by propagating and further travel in the extension direction of the axis. The inclination angle of the flat plate member with respect to the axis to be filled, the material of the flat plate member, and the thickness of the flat plate member are set.

  In the present invention, the “coincidence effect”, which is a problem in sound insulation performance of a plate glass or the like, is used for an ultrasonic probe. For example, when external noise (sound wave) is incident on the window glass (flat plate member), sound waves having a normal frequency are absorbed by the window glass (flat plate member) and attenuated (transmission loss occurs), so that the sound insulation effect is obtained. Will be obtained. On the other hand, when a sound wave in a specific frequency band enters and a component parallel to the flat plate member resonates as a bending wave (Lamb wave) propagating on the flat plate member, the sound wave passes through the window glass (transmission loss decreases). The sound insulation effect cannot be obtained. This phenomenon is known as the coincidence effect.

In the present invention, the ultrasonic signal is transmitted through the positive effect of the coincidence effect with respect to the flat plate member inclined on the axis of the ultrasonic signal emitted from the main probe. Specifically, by selecting the inclination angle, material, and thickness of the flat plate member according to the frequency of the ultrasonic signal generated by the main probe and the material of the propagating body in the probe holder, the incident ultrasonic signal is The Lamb waves are propagated by resonating with the flat plate member, and the ultrasonic wave signal is transmitted straight in the extending direction of the axis through the flat plate member.
On the other hand, the sub-probe is mounted on the probe holder so that the irradiated ultrasonic energy is reflected by the flat plate member and is irradiated in the extension direction of the axis of the main probe (setting the angle attached to the probe holder).
As a result, the ultrasonic signal from the main probe passes through the fixed flat plate member by using the coincidence effect, thereby going straight in the extending direction of the axis. Further, the ultrasonic energy from the sub probe is reflected by the fixed flat plate member and proceeds in the extending direction of the axis of the main probe.

  In the ultrasonic frequency band of 2 MHz to 15 MHz used in the fat diagnostic ultrasonic probe, the plate member is propagated in the “Lamb wave A0 mode” by analysis calculation described later.

Here, the frequency of the ultrasonic signal from the main probe is preferably in the range of 2 MHz to 15 MHz, and the ultrasonic energy for heating from the sub probe is preferably in the range of 0.5 MHz to 2 MHz.
As a result, it becomes possible to warm the living body deeply with ultrasonic energy in the range of 0.5 MHz to 2 MHz, and in the range of 2 MHz to 15 MHz that is used in normal ultrasonic image diagnosis (B-mode image diagnosis) of the liver. By transmitting a sound wave signal and receiving an ultrasonic echo signal, it can be applied to the diagnosis of fatty liver.

  The plate thickness of the flat plate member is desirably set to 0.02 mm to 2 mm. If the thickness of the flat plate member is thinner than this, the flat plate member is likely to be damaged and easily affected by noise such as external vibration. On the contrary, if the plate thickness of the flat plate member is larger than this, the absorption of ultrasonic waves by the flat plate member becomes large, and it becomes difficult for the ultrasonic signal from the main probe to pass through the flat plate member with sufficient strength.

In the above invention, the inclination angle of the flat plate member relative to the axis may be approximately 45 °.
By setting the inclination angle of the flat plate member with respect to the axis of the ultrasonic signal from the main probe to about 45 °, the direction of the ultrasonic energy emitted from the sub-probe is set substantially to the axis of the ultrasonic signal from the main probe. Since the angle can be set to 90 °, the emission direction of the main probe may be set to the vertical direction, and the emission direction of the sub probe may be set to the horizontal direction, and the angle adjustment when attaching each probe to the upper surface and the side surface of the probe holder becomes easy .

In the above invention, the material of the flat plate member may be a metal plate, a glass plate, or another solid plate capable of propagating Lamb waves.
Here, aluminum, iron, stainless steel or the like can be used for the metal plate. As the glass plate, soda glass, quartz glass or the like can be used. A resin plate such as an acrylic plate can also be used. Furthermore, other materials can be used as long as the surface is flat and Lamb waves can propagate.
The propagating body may be water, oil, or other liquid material.
Here, silicone oil, lubricating oil, spindle oil, edible oil, and the like can be used as the oil. Moreover, other liquid materials, such as acetone and alcohol, may be sufficient.

Further, the probe holder may be attached such that flat plate members having different plate thicknesses can be replaced according to the frequency of the ultrasonic signal.
By replacing the main probe with a different frequency and attaching it to the probe holder, and replacing the flat plate member accordingly, fat diagnosis at a different frequency becomes possible.
If the material of the flat plate member and the propagating body is fixed to one type, the number of flat plate members having different plate thicknesses when changing according to the frequency of the main probe can be reduced. If the types of body selection are increased, it is necessary to increase the number of plate members for replacement accordingly.

  According to the present invention, it is possible to realize an ultrasonic probe for fat diagnosis capable of irradiating with an axis of an ultrasonic signal from a main probe and an ultrasonic energy from a sub probe being coaxial without using a drive mechanism. be able to.

Sectional drawing which shows the structure of the ultrasonic probe for fat diagnosis which is one Embodiment of this invention. The figure which shows the structure of a subprobe. 1 is an external view showing an example of a fat diagnosis system using an ultrasonic probe for fat diagnosis of the present invention. The block diagram which shows the structure of the fat diagnostic system of FIG. The figure which shows the measurement system of the transmission confirmation experiment in embodiment of this invention. The figure which shows the waveform of the transmission ultrasonic signal in the transmission confirmation experiment. The figure which shows the waveform of the transmission ultrasonic signal in the transmission confirmation experiment. The figure which shows the waveform of the transmission ultrasonic signal in the transmission confirmation experiment. The figure which shows a phase velocity dispersion | distribution curve when using a flat plate member as an aluminum plate. The schematic diagram which shows the ultrasonic echo signal before and after heating. The figure which shows the conventional ultrasonic probe for fat diagnosis.

  An embodiment of the present invention will be described. In the following, first, an overall structure of an ultrasonic probe for fat diagnosis according to the present invention and an overall configuration of a fat diagnosis system using the same will be described. Subsequently, a transmission confirmation experiment using the coincidence effect will be described, and a description of the Lamb wave A0 mode related to the present invention and its use will be described.

  FIG. 1 is a cross-sectional view showing a configuration of an ultrasonic probe for fat diagnosis according to an embodiment of the present invention. The ultrasonic probe 1 includes a multi-channel main probe 2 for diagnosis and a probe holder 5 for attaching and holding a one-channel sub probe 4 for heating.

As the main probe 2, an array type probe (commercially available) of multi-channel (for example, 128 transducers) is used, and a pulse wave ultrasonic signal is transmitted from each channel while scanning, and ultrasonic waves from a living body are transmitted. An echo signal is received. When the same number of ultrasonic echo signals as the number of channels are sent to an ultrasonic diagnostic apparatus 11 (FIG. 3) described later, an ultrasonic image such as a B-mode image is formed and displayed on the display screen of the ultrasonic diagnostic apparatus 11. Is done.
Since one ultrasonic signal is emitted from each channel of the main probe 2, there are as many “axis lines” as the traveling direction of the ultrasonic signal as the number of emitted ultrasonic waves. Among these, the ultrasonic energy for heating from the sub-probe 4 and one axis that becomes coaxial after passing through the flat plate member 5a are referred to as “axis L”.
In the present embodiment, the axis of one line of ultrasonic signal irradiated from the central piezoelectric element among the multi-channel piezoelectric elements is selected as “axis L”, and the ultrasonic wave emitted from the sub probe 4 is selected. The energy is also attached to the probe holder 5 so as to be irradiated coaxially around the axis L after being reflected by the flat plate member 5a.

  The center frequency of the ultrasound emitted from the main probe 2 is selected from the range of 2 MHz to 15 MHz according to the depth of the measurement site and the resolution of the image, as in normal image diagnosis. . Here, for example, a piezoelectric element (transducer) that oscillates an ultrasonic wave of 5 MHz is used.

As the sub probe 4, as shown in FIG. 2, a cylindrical probe composed of a one-channel vibrator 4 a is used. The vibrator 4a uses a high-power piezoelectric element capable of irradiating heating ultrasonic waves, and a heat radiating member is provided around the vibrator 4a. The sub probe 4 is compared with the main probe 2. It has a tough structure and is designed to provide sufficient heat dissipation.
The center frequency of the ultrasonic energy irradiated from the sub probe 4 is selected from the range of 0.5 MHz to 2 MHz so that the absorption by the living body is small and the living body can be heated deeply.

The probe holder 5 is a rectangular body surrounded on all sides by side walls 5b, and the upper surface is an opening 5c into which the main probe 2 having a horizontal cross section is square. An opening 5e is formed on one surface of the side wall 5b, and the sub probe 4 is attached thereto.
The lower surface has an opening (emission port) 5d for emitting ultrasonic signals from the main probe 2 and ultrasonic energy from the sub-probe 4, and a sheet 5f made of silicone rubber or the like through which these ultrasonic waves can pass is used as a window material. The opening 5d is closed. The sheet 5f is provided to fill the probe holder 5 with a fluid propagating body 3 that propagates ultrasonic waves. Moreover, you may make it use as an acoustic lens which suppresses spreading | diffusion of an ultrasonic wave.
The propagation body 3 is made of a material having a known sound speed such as water or oil (for example, the sound speed of water at 37 ° C. is 1524 m / s).
The propagation body 3 and the sheet 5f are preferably close to acoustic impedance. When silicone rubber is used as the sheet 5f (acoustic lens), the speed of sound of the silicone rubber is about 1000 m / s. Therefore, from the point of impedance matching, silicone oil (1275 m / s) having a relatively close sound speed is used for the propagation body 3. It is preferable to use a material.

  In the probe holder 5, a flat plate member 5 a is fixed on the axis L of the ultrasonic signal emitted from the main probe 2 so as to be inclined by 45 ° with respect to the axis L. The flat plate member 5a is also inclined by 45 ° with respect to the axis of the ultrasonic wave emitted from another channel other than the axis L of the main probe 2.

The flat plate member 5a is attached with a plate thickness that allows the ultrasonic signal from the main probe 2 to pass therethrough. Specifically, the transmission performance is most excellent in a state where it is inclined at 45 ° with respect to the axis L of the main probe 2 in advance by a method similar to the transmission confirmation experiment described later from among a plurality of candidates having different plate thicknesses. In other words, a plate having an optimum plate thickness that satisfies the conditions (resonance conditions) through which Lamb waves can propagate is experimentally determined and adopted as the flat plate member 5a.
Regarding the optimization of the flat plate member 5a at this time, a method of deriving a velocity distribution curve (FIG. 8) representing the propagation characteristic of Lamb waves and utilizing this for optimization of the plate thickness and the like is preferable. It will be described later.

  Next, a usage mode of the above-described fat diagnostic ultrasonic probe 1 will be described. FIG. 3 is an external view showing a fat diagnostic system 10 using the fat diagnostic ultrasonic probe 1 according to the present invention, and FIG. 4 is a block diagram for explaining the configuration of the fat diagnostic system 10.

  The fat diagnostic system 10 includes an ultrasonic probe 1 for fat diagnosis described in FIG. 1 (including a main probe 2, a sub probe 4, a probe holder 5, and a flat plate member 5a), an ultrasonic diagnostic apparatus 11, and a control box. 12 and an external computer device 13.

The ultrasonic diagnostic apparatus 11 is provided with an external output terminal through which a raw ultrasonic echo signal (RF signal) received through the main probe 2 can be extracted. In addition, some of the commercially available ultrasonic diagnostic devices do not have such an external output terminal. In that case, the external output terminal can be removed by a simple operation such as installing an expansion card for expanding the external output terminal. Add more.
The ultrasonic diagnostic apparatus 11 transmits an ultrasonic echo signal from the external output terminal to the control box 12 via the signal cable 14.

  The control box 12 is a pulser / receiver circuit 33 that receives an ultrasonic echo signal transmitted from the external output terminal of the ultrasonic diagnostic apparatus 11 via the signal cable 14, and converts the received ultrasonic echo signal into a digital signal. And a buffer memory 35 for performing transmission speed adjustment processing for sending out an ultrasonic echo signal to the external computer device 13. In addition, a high-frequency power source 31 that generates a continuous ultrasonic wave for heating for irradiation from the sub probe 4 via the signal cable 15 is provided. Furthermore, a controller 36 that controls the irradiation of ultrasonic energy from the sub-probe 4, controls the start and stop of reception of the ultrasonic echo signal by the pulser / receiver circuit 33, and controls the transmission of the ultrasonic echo signal by the buffer memory 35. It has.

  As the external computer device 13, a general-purpose personal computer device (for example, a notebook computer) including a CPU, a memory, an input device (such as a keyboard), and a display device (liquid crystal panel) is used. An ultrasonic echo signal measured by the ultrasonic diagnostic apparatus 11 and the main probe 2 and transmitted via the signal cable 14 and the control box 12 is received. The ultrasonic echo signal receives at least the number of ultrasonic echo signals included in the region that can be heated by the sub probe 4. Since this ultrasonic echo signal is measured twice before and after heating without moving the main probe 2, the ultrasonic echo signal before heating and the ultrasonic echo after heating are respectively measured. As the “signal”, the same number of ultrasonic echo signal data is stored.

Then, the pre-heating ultrasonic echo signal and the post-heating ultrasonic echo signal are calculated according to the above-described equation (2) to calculate the ultrasonic velocity change (in this case, the ultrasonic velocity ratio), and for fat diagnosis Perform the necessary arithmetic processing.
That is, based on the ultrasonic echo signal received after heating and the ultrasonic echo signal received before heating, using the same principle and method as the conventional example described in FIG. A waveform shift amount (Δτ) of the acoustic echo signal is calculated, and a process of calculating a pulse interval (τ) between tissue boundaries in the measurement region is performed. And based on Formula (2), the process which calculates the ultrasonic velocity ratio (V '/ V) of each partial area is performed.

In the external computer device 13, since a plurality of ultrasonic echo signal data received by the main probe 2 is processed, the calculation result is an ultrasonic velocity change image or fat distribution for the region heated by the sub probe 4. The amount of data is such that an image can be formed. Therefore, an ultrasonic velocity change image and further a fat distribution image can be displayed on the display screen of the external computer device 6 by the transmitted ultrasonic echo signal data.
In addition, if a specific measurement point is specified on the displayed screen, the calculation result of the ultrasonic velocity ratio value and fat information (fat determination, fat ratio) is calculated based on the ultrasonic echo signal corresponding to the measurement point. It can also be expressed numerically on the display device.

(Ultrasonic signal transmission confirmation experiment)
An experimental result for confirming that the ultrasonic signal travels straight through the flat plate member due to the coincidence effect will be described. FIG. 5 is a diagram showing a measurement system used in the experiment.
In a container filled with water as a propagation body of an ultrasonic signal, a transmitting side transducer is arranged on the upper side and a receiving side transducer is arranged on the lower side with a flat plate member interposed therebetween. The flat plate member is designed so that the inclination angle θ can be adjusted by setting the horizontal direction to 0 °.
The pulsar / receiver circuit (PANAMETRICS-NDT, Model5077R) outputs an ultrasonic signal of a 5 MHz pulse wave to the transmission side transducer and also receives a transmission ultrasonic signal received by the reception side transducer. This transmitted ultrasonic signal is detected by an oscilloscope.
An aluminum thin plate was used as the flat plate member, and ultrasonic transmission characteristics when the plate thickness and the inclination angle were changed were confirmed.

FIG. 6 is a diagram showing a waveform of a transmission ultrasonic signal in which transmission characteristics are measured at plate thicknesses t of 0.1 mm, 0.2 mm, and 0.3 mm and inclination angles θ of 0 ° and 45 °. For comparison, a transmitted ultrasonic signal (referred to as a raw signal) directly received without providing a flat plate member is also shown.
When the inclination angle is 0 °, the transmitted ultrasonic signal is greatly attenuated compared to the raw signal, and the attenuation is particularly increased as the plate thickness is increased.
When the inclination angle is 45 °, the transmitted ultrasonic signal when the plate thickness is 0.3 mm is greatly attenuated, but when the plate thickness is 0.2 mm and 0.1 mm, it is not so attenuated. The intensity ratio of the transmitted ultrasonic signal to the raw signal at .2 mm is 90% and has excellent transmission characteristics.

  FIG. 7 is a diagram showing a waveform of a transmitted ultrasonic signal when the thickness t of the flat plate member is 0.2 mm and the inclination angle is changed from 0 ° to 70 °. The transmitted sound wave signal is maximum when the inclination angle is 46 °.

  From the above, when the propagating body is water, the material of the flat plate member is an aluminum plate, and the ultrasonic frequency is 5 MHz, if the inclination angle is set to about 45 °, the plate thickness is processed to 0.2 mm. Thus, it was confirmed that the ultrasonic signal can pass through the flat plate member due to the coincidence effect.

  Changing the propagation material (water, oil), flat plate material (glass, other metals), ultrasonic frequency (2 MHz to 15 MHz), tilt angle, and plate thickness, the resonance conditions for obtaining the coincidence effect change Therefore, it goes without saying that the present invention can be implemented under other conditions by changing any of these parameters to experimentally search for the optimum conditions.

(Analysis of ultrasonic wave propagation in flat plate member)
As described above, the conditions (resonance conditions) for obtaining the coincidence effect are experimentally determined by preliminarily determining initial values of parameters such as plate thickness and ultrasonic signal and changing the parameters within an appropriate range. However, it is preferable to use the propagation characteristics theoretically derived from the wave equation when setting the initial values of the parameters for optimization.
Ultrasonic waves propagating in a flat plate member are represented by the Rayleigh-Lamb equation derived from the wave equation. From this equation, research has been conducted to calculate a dispersion curve of the phase velocity of a lamb wave, which is a plate wave. Therefore, this is utilized (for example, refer to the following document A).

Reference A: Tohoku Branch of the Society of Instrument and Control Engineers, 251st Meeting (2009.7.15) “Propagation Analysis of Guide Waves in Flat Plates” Shuhei Takamura, Kazuhiko Konno Faculty of Engineering Resources, Akita University

When ultrasonic waves are obliquely incident on the flat plate member, Lamb waves propagate through the flat plate member. The Lamb wave includes an S mode (Symmetric) in which the upper and lower surfaces of the flat plate member are expanded and contracted symmetrically and an A mode (Anti-symmetric) in which the upper and lower surfaces are asymmetrically expanded and contracted. The S mode has S0, S1, S2... Modes in the order from the basic mode to the higher order mode, and the A mode has A0, A1, A2.
The propagation characteristics of the S mode and the A mode can be represented by the following equation (3) for the S mode and the following equation (4) for the A mode, which is called the Rayleigh-Lamb equation.
Then, the velocity dispersion curve of the phase velocity c of the Lamb wave (bending wave) can be calculated by the following equation (5).

Here, k is the wave number, d is the plate thickness, ω is the angular frequency, and c is the phase velocity of the Lamb wave. c _{T, c L} the shear wave velocity determined by the flat member material, a longitudinal wave sonic speed.

FIG. 8 is a diagram showing a calculated phase velocity dispersion curve assuming that the material of the flat plate member is an Al (aluminum) plate (that is, c _T = 6400 m / s, c _L = 3040 m / s).
On this dispersion curve, the vertical axis is the phase velocity c, and the horizontal axis is ultrasonic frequency × plate thickness. When the ultrasonic wave transmitted from the external propagation body (water) is obliquely incident on the flat plate member, the sound velocity V _w (for example, 1524 m / s) of the external propagation body (water) and the propagation speed in the flat plate member V (= c) means that the following equation (6) is satisfied from the geometric relationship, so that the sound pressure distribution of the external propagation body (water) is synchronized on the flat plate member, and the ultrasonic wave is propagated to the flat plate member. It will be.
Vsin α = V _w (6)
Here, α is an incident angle and has a relationship of θ + α = 90 °.

Then, the ultrasonic frequency is 5 MHz, the plate thickness t (= d) is 0.2 mm, and the phase velocity V of the propagation mode in which propagation is possible is read from the phase velocity dispersion curve of FIG. 8 (horizontal axis “frequency × plate thickness” Phase velocity when A is 1 MHz mm), A0 mode (about 2200 m / s) and S0 mode (5400 m / s),
Α that can satisfy Expression (6) exists in the A0 mode.
That is, from the sound velocity V _w = 1524 m / s of water and the phase velocity V = 2200 m / s of the A0 mode,
sin α = 1540/2200
And
Propagation is possible at α = 44 °.

  In the experimental results of FIG. 7, the transmission characteristics are the best when θ = 46 ° (that is, α = 44 °). This corresponds to the fact that the ultrasonic signal propagates through the flat plate member in the A0 mode. doing.

  Propagation in the S0 mode (V = 5400 m / s) is θ = 73 ° to 74 ° (α = 16 ° to 17 °), and the incident angle to the flat plate member is too shallow, so the transmission characteristics in the S0 mode are used. It is difficult to do.

In the above example, the frequency (f) and the plate thickness (t) are determined first, and the phase velocity (V) and the external sound velocity (V) in the A0 mode corresponding to “frequency × plate thickness” determined from them are determined. The incident angle α is obtained from V _w ).
On the other hand, the incident angle α (for example, α = 45 ° (that is, θ = 45 °)) and the sound velocity V _w (1524 m / s for water) of the external propagation body (water) are determined first, The value of “ultrasonic frequency × plate thickness” of the A0 mode corresponding to the value of the phase velocity (V) uniquely calculated from the equation (6) is read from FIG. 8, and the plate is selected according to the ultrasonic frequency to be used. The thickness may be determined, or the ultrasonic frequency may be determined according to the plate thickness to be used.

  Then, by using the parameter determined using the phase velocity dispersion curve as an initial value and finely adjusting the plate thickness of the flat plate member, a flat plate member with excellent propagation characteristics can be easily obtained.

In the above, the inclination angle θ of the flat plate member 5a is 45 °, the material is an aluminum plate, the propagation body is water, and the ultrasonic frequency is 5 MHz. However, it goes without saying that any parameter may be changed. Nor.
For example, the inclination angle θ for attaching the flat plate member 5a may be changed within a range of about 30 ° to 60 °. In this case, it is necessary to adjust the angle at which the sub probe 4 is attached to the probe holder 5 so that the axis of the sub probe 4 after being reflected by the flat plate member 5a is coaxial with the axis L.
Further, the flat plate member 5a may be changed to a glass plate, a stainless plate, or the like. In that case, the speed of sound (c _T , c _L ) in the flat plate member 5a in the equation (5) is changed for each material, and the velocity dispersion curve for each material is calculated.
Further, when the propagation material 3 is changed from water to oil, comprising a sound velocity V _w to be calculated by changing the speed of sound of the oil.

  The present invention can be used as an ultrasonic probe for fat diagnosis.

1 Ultrasonic probe for fat diagnosis 2 Main probe (multichannel ultrasonic probe for diagnosis)
3 Propagation body (water)
4 Sub probe (Ultrasonic probe for heating)
4a 1 channel transducer 5 probe holder 5a flat plate member 11 ultrasonic diagnostic device 12 control box 13 external computer device 14, 15 signal cable 31 high frequency power supply 33 pulser / receiver circuit 34 A / D converter 35 buffer memory 36 controller

Claims (7)

A main probe and a sub-probe are mounted on the probe holder, and a diagnostic ultrasonic signal emitted from the main probe and a heating ultrasonic energy emitted from the sub-probe are filled in the probe holder. A diagnostic ultrasound probe for fat diagnosis that propagates through the propagation body and irradiates the subject,
The probe holder is disposed so as to incline so that the ultrasonic signal from the main probe travels straight through the propagating body so that the axis is obliquely incident, and is emitted from the sub probe. A flat plate member that reflects energy and irradiates in the extending direction of the axis is fixed,
The flat plate member passes through the flat plate member as the ultrasonic signal from the main probe propagates in the flat plate member with propagation characteristics of a Lamb wave A0 mode, and further proceeds in the direction of extension of the axis. According to the frequency of the ultrasonic signal and the material of the propagating body, the inclination angle of the flat plate member with respect to the axis satisfying the propagation condition of the Lamb wave A0 mode, the material of the flat plate member, the thickness of the flat plate member An ultrasonic probe for fat diagnosis, characterized in that is set.   The fat according to claim 1, wherein the frequency of the ultrasonic signal from the main probe is in a range of 2 MHz to 15 MHz, and the ultrasonic energy for heating from the sub probe is in a range of 0.5 MHz to 2 MHz. Diagnostic ultrasound probe.   The ultrasonic probe for fat diagnosis according to claim 1 or 2, wherein the plate member has a thickness of 0.02 mm to 2 mm.   The ultrasonic diagnostic probe for fat diagnosis according to any one of claims 1 to 3, wherein an inclination angle of the flat plate member with respect to the axis is approximately 45 °.   The fat probe ultrasonic probe according to any one of claims 1 to 4, wherein a material of the flat plate member is a metal plate, a glass plate, or another solid plate capable of propagating Lamb waves.   The fat diagnostic ultrasonic probe according to any one of claims 1 to 5, wherein the propagating body is water, oil, or other liquid material.   The fat probe ultrasonic probe according to any one of claims 1 to 6, wherein the flat plate member having a plate thickness different according to the frequency of the ultrasonic signal is attached to the probe holder in a replaceable manner.