JP4654352B2 - Ultrasonic inspection method and ultrasonic inspection apparatus - Google Patents

Description

  The present invention relates to an ultrasonic inspection method and an ultrasonic inspection apparatus that inspect a living tissue such as skin using ultrasonic waves.

Conventionally, in the medical field, an ultrasonic inspection apparatus for diagnosing the inside of a human body using ultrasonic waves has been put into practical use (see, for example, Patent Document 1). In the apparatus of Patent Document 1, an ultrasonic probe unit that irradiates an ultrasonic wave is directly applied to an examination part of a human body, and a signal of a reflected wave reflected by an organ or the like is image-processed to diagnose the inside of the human body. In addition, the apparatus includes two ultrasonic vibrators, a low-frequency vibrator and a high-frequency vibrator, so that two types of ultrasonic waves having different frequencies can be irradiated. Ultrasonic waves have a characteristic that the lower the frequency (that is, the longer the wavelength), the deeper the incident inside the human body. Therefore, a high-frequency vibrator is used for diagnosis of a shallow part in the human body, and a low-frequency vibrator is used for diagnosis of a deep part.
JP 2004-305451 A

  By the way, human skin has a layer structure, and is in the order of epidermis, dermis, and subcutaneous tissue from the surface side. Recently, there is a demand for obtaining information on each layer in the skin (for example, the thickness and hardness of the layer) and using it for examination. Then, by utilizing the above characteristic that the lower frequency ultrasonic waves are more likely to enter the human body, it is possible to obtain skin layer information. However, in the apparatus of Patent Document 1, since only two types of ultrasonic frequencies can be switched, it is difficult to accurately acquire skin layer information having a three-layer structure. In addition, the thickness of each layer of the skin varies from person to person, and even the same person has a difference depending on the region. Therefore, it is practically extremely difficult to obtain such information accurately.

  If skin layer information is to be acquired using a conventional ultrasonic examination apparatus, for example, a function of measuring the number of times by switching the ultrasonic wave to a plurality of types of frequencies is required. Accordingly, there arises a problem that the circuit configuration such as the pulse generation circuit becomes complicated and the price of the apparatus is increased, and the measurement time is increased. Moreover, even if such a device can be realized, it is expected that accurate acquisition of skin layer information is still difficult.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an ultrasonic inspection method capable of accurately and quickly acquiring layer information of a living tissue. Another object of the present invention is to provide an ultrasonic inspection apparatus having a relatively simple structure even though layer information of a living tissue can be acquired accurately and quickly.

In order to solve the above-mentioned problem, in the invention according to claim 1, an ultrasonic inspection method in which a living tissue having a layer structure is irradiated with ultrasonic waves, and the living tissue is inspected based on the obtained reflected wave. A first step of irradiating the living tissue with ultrasonic waves that are pulse-excited and having different frequency components, and an acoustic impedance for different frequencies based on a reflected wave from the living tissue And calculating a sound impedance curve indicating a correlation between the frequency and the sound impedance by performing a second step of obtaining hardness information at different depths in the living tissue. And determine that there is a layer interface at a depth corresponding to the frequency where the slope of the acoustic impedance curve is greater than the specified value. With, the ultrasonic inspection method characterized by determining the thickness of each layer and its gist. In addition, the ultrasonic wave containing a different frequency component refers to the ultrasonic wave which has a frequency band of a certain wide width, for example, the ultrasonic wave which has a frequency band of several MHz-several hundred MHz is suitable.

  Therefore, according to the first aspect of the present invention, ultrasonic waves that are pulse-excited and include different frequency components are irradiated toward a living tissue having a layer structure. At this time, high-frequency ultrasonic waves are reflected on the surface of the biological tissue, whereas low-frequency ultrasonic waves are transmitted through the surface of the biological tissue and are reflected inside the tissue. Therefore, if the acoustic impedance for different frequencies is calculated based on the reflected wave from the biological tissue, the hardness information at different depths in the biological tissue can be obtained. In this measurement method, since ultrasonic waves containing different frequency components can be obtained by pulse excitation, it is not necessary to switch to ultrasonic waves of different frequencies and perform measurement many times as in the prior art. Therefore, the layer information in the living tissue can be acquired quickly and accurately by one measurement, which can be used for examination.

In the above invention, an acoustic impedance curve indicating the correlation between frequency and acoustic impedance is obtained by calculation, and there is a layer interface at a depth corresponding to the frequency at a location where the slope is larger than a predetermined value in the acoustic impedance curve. as well as determination, it determines the thickness of each layer.

In a living tissue having a layer structure, the acoustic impedance of each layer is different, and the acoustic impedance changes greatly at the interface of each layer. According to the above-described invention, by determining the frequency of the portion where the slope is larger than the predetermined value in the acoustic impedance curve, the depth at which the interface of the layer is present can be determined, and the thickness of the layer can be determined by the position of the interface. Can be determined .
The invention according to claim 2 is the invention according to claim 1, wherein, in the second step, the hardness of different layers is determined by obtaining acoustic impedances on the low frequency side and the high frequency side across the frequency of the part. The gist is an ultrasonic inspection method characterized in that it is obtained.
According to the second aspect of the present invention, it is possible to determine the depth at which the interface of the layer is present by determining the frequency of the portion where the slope is larger than the predetermined value in the acoustic impedance curve. And the hardness information of the lower layer side and the upper layer side from the interface can be obtained by obtaining the acoustic impedance on the low frequency side and the high frequency side of the frequency of the portion where the inclination is large.

The invention according to claim 3 is an ultrasonic inspection method for irradiating a living tissue having a layer structure with ultrasonic waves, and inspecting the living tissue based on the obtained reflected wave, and is pulse-excited. A first step of irradiating the living tissue with ultrasonic waves including different frequency components, and calculating an acoustic impedance for different frequencies based on a reflected wave from the living tissue; A second step for obtaining hardness information at different depths in the tissue, and in the second step, an acoustic impedance curve indicating a correlation between the frequency and the acoustic impedance is obtained by calculation, and an inclination is determined in the acoustic impedance curve. It is determined that there is a layer interface at a depth corresponding to the frequency at a location where is greater than a predetermined value, and the frequency at the location is determined. Sandwiched therebetween by determining the low frequency side and the acoustic impedance of the high-frequency side, respectively, as its gist the ultrasonic inspection method characterized by determining the hardness of the different layers.

According to the third aspect of the present invention, ultrasonic waves that are pulse-excited and include different frequency components are irradiated toward a living tissue having a layer structure. At this time, high-frequency ultrasonic waves are reflected on the surface of the biological tissue, whereas low-frequency ultrasonic waves are transmitted through the surface of the biological tissue and are reflected inside the tissue. Therefore, if the acoustic impedance for different frequencies is calculated based on the reflected wave from the biological tissue, the hardness information at different depths in the biological tissue can be obtained. In this measurement method, since ultrasonic waves containing different frequency components can be obtained by pulse excitation, it is not necessary to switch to ultrasonic waves of different frequencies and perform measurement many times as in the prior art. Therefore, the layer information in the living tissue can be acquired quickly and accurately by one measurement, which can be used for examination. Further, by determining the frequency of the portion where the slope is larger than the predetermined value in the acoustic impedance curve, the depth at which the interface of the layer is present can be determined. And the hardness information of the lower layer side and the upper layer side from the interface can be obtained by obtaining the acoustic impedance on the low frequency side and the high frequency side of the frequency of the portion where the inclination is large.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, in the first step, the first step is pulse-excited, includes different frequency components, and focuses on a surface layer portion of the living tissue. The gist of the present invention is to irradiate the living body tissue with two-dimensional scanning with an ultrasonic wave that converges as follows.

  Therefore, according to the fourth aspect of the invention, in addition to the information on the depth direction of the living tissue, the information on the plane direction can be acquired. That is, three-dimensional information in the living tissue can be acquired, and the living tissue can be examined more accurately. Moreover, since the ultrasonic waves converge with the surface layer portion of the living tissue as a focal point, it is possible to grasp the fine structure in the living tissue.

  The gist of the fifth aspect of the present invention is that, in any one of the first to fourth aspects, the biological tissue is skin.

  Therefore, according to the invention described in claim 5, the thickness and hardness information of each layer of the epidermis, dermis and subcutaneous tissue constituting the skin can be acquired, and the health condition of the skin can be inspected accordingly. It becomes possible.

The invention described in claim 6 is directed to any one of claims 1 to 3 in which the living tissue having a layer structure is irradiated with ultrasonic waves and the living tissue is inspected based on the obtained reflected wave. An ultrasonic inspection apparatus that executes the method according to claim 1, wherein the ultrasonic wave that is pulse-excited and includes different frequency components is irradiated toward the biological tissue, and a reflected wave from the biological tissue is emitted. Obtaining hardness information at different depths in the living tissue by calculating an acoustic impedance for different frequencies based on an ultrasonic transducer that receives and converts it into an electrical signal and a reflected wave from the living tissue The gist of the present invention is an ultrasonic inspection apparatus comprising a computing means.

  According to the sixth aspect of the present invention, ultrasonic waves that are pulse-excited and include different frequency components by the ultrasonic transducer are irradiated toward a living tissue having a layer structure. At this time, high-frequency ultrasonic waves are reflected on the surface of the biological tissue, whereas low-frequency ultrasonic waves are transmitted through the surface of the biological tissue and are reflected inside the tissue. Then, the calculation means calculates the acoustic impedance for different frequencies based on the reflected wave from the living tissue, and obtains hardness information at different depths in the living tissue. According to this device, ultrasonic waves containing different frequency components can be obtained by pulse excitation, so there is no need for a complicated circuit configuration for switching to ultrasonic waves of different frequencies, and the structure is compared. Simple. In addition, layer information in a living tissue can be acquired quickly and accurately by a single measurement, which can be used for examination.

  The gist of the invention described in claim 7 is that, in claim 6, it further comprises image generating means for performing processing for generating image data indicating hardness information at different depths in the living tissue.

  Therefore, according to the seventh aspect of the present invention, the image generating means generates image data indicating hardness information at different depths in the living tissue, so that the cross-sectional structure of the living tissue can be easily visualized. Can do.

  The invention according to claim 8 is the ultrasonic transducer according to claim 6 or 7, further comprising two-dimensional scanning means for two-dimensionally scanning the ultrasonic irradiation point along the surface of the living tissue. The gist thereof is that it has a function of focusing and irradiating the ultrasonic wave with the surface layer portion of the living tissue as a focal point.

  Therefore, according to the eighth aspect of the invention, in addition to the information on the depth direction of the living tissue, the information on the plane direction can be acquired by the two-dimensional scanning unit. That is, three-dimensional information in the living tissue can be acquired, and the living tissue can be examined more accurately. Moreover, since the ultrasonic waves converge with the surface layer portion of the living tissue as a focal point, it is possible to grasp the fine structure in the living tissue.

  As described in detail above, according to the first to fifth aspects of the invention, it is possible to provide an ultrasonic inspection method capable of accurately and quickly acquiring layer information of a living tissue. In addition, according to the inventions described in claims 6 to 8, it is possible to provide an ultrasonic inspection apparatus having a relatively simple structure even though layer information of a living tissue can be acquired accurately and quickly.

[First Embodiment]

  DESCRIPTION OF EMBODIMENTS A first embodiment embodying the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an ultrasonic inspection apparatus 1 according to the present embodiment.

  The ultrasonic inspection apparatus 1 includes an ultrasonic probe unit 2 and a personal computer (personal computer) 3. The ultrasonic probe unit 2 and the personal computer 3 are connected via, for example, a USB cable 4.

  The ultrasonic probe unit 2 includes an ultrasonic probe 5 and a handpiece part 6 to / from which the ultrasonic probe 5 can be attached / detached. The ultrasonic probe 5 has a function of irradiating an inspection object while scanning ultrasonic waves two-dimensionally, converting a reflected wave from the inspection object into an electric signal, and outputting the electric signal. The handpiece portion 6 is a so-called gripping portion, and has a length and a diameter that can be gripped by a hand. Therefore, the ultrasonic probe unit 2 is used by, for example, a doctor or the like to examine the skin health of the examinee. In this case, the user holds the handpiece unit 6 by hand and directly touches the ultrasonic probe 5 against the skin of the examinee.

  Specifically, the ultrasonic probe 5 includes a probe case 11, a transducer 12 as an ultrasonic transducer, a first rotor portion 13 and a second rotor portion 14 as two-dimensional scanning means, and a reference member 15. Prepare. The probe case 11 has a known acoustic impedance different from that of a living tissue, and a tip portion is formed in a substantially hemispherical shape using a material (for example, acrylic resin) that can transmit ultrasonic waves. The probe case 11 is filled with an ultrasonic transmission medium (specifically pure water) W.

  In the present embodiment, the first rotor portion 13 and the second rotor portion 14 are accommodated in the probe case 11, and two transducers are provided on the outer peripheral surface of the first rotor portion 13 provided on the front end side of the case. 12 is provided. These two transducers 12 are made of a polymer-based piezoelectric material, and are provided at a position 180 degrees away from the rotation axis 13 a of the first rotor portion 13. With this configuration, the weight balance around the rotation shaft 13a is improved, so that the occurrence of vibrations can be reliably prevented.

  The ultrasonic waves irradiated by the transducer 12 are converged in a conical shape via the ultrasonic transmission medium W and focused on the outer surface of the probe case 11. In the present embodiment, for example, a transducer having a diameter of 3 mm, a height of 3 mm, and a bandwidth of about several MHz to several hundred MHz is used as the transducer 12.

  In the present embodiment, the first rotor portion 13 is rotatably supported by the housing 17 via a rotation shaft 13 a parallel to the short direction of the ultrasonic probe unit 2. Further, the second rotor portion 14 supports the housing 17 via a rotating shaft 14 a parallel to the longitudinal direction of the ultrasonic probe unit 2, and rotates the first rotor portion 13 together with the housing 17. These rotor parts 13 and 14 are comprised with the known electric motor which can control a rotational speed and a rotation position. The power supply to the first rotor unit 13 and the transmission / reception of electric signals to the transducer 12 are performed via a slip ring (not shown).

  In addition, a reference member 15 is provided in a range where the ultrasonic irradiation point is scanned on the outer surface of the probe case 11. The reference member 15 of the present embodiment is formed of, for example, an epoxy resin. Therefore, the reference member 15 has a known acoustic impedance different from the probe case 11 made of acrylic resin.

  In the hand piece portion 6 of the ultrasonic probe unit 2, a rotor control circuit 21 for driving and controlling the rotor portions 13 and 14, a signal processing circuit 22 for transmitting and receiving ultrasonic waves, and an input / output of electric signals An I / F circuit 23 and the like are provided. As the I / F circuit 23, a USB interface which is a standard interface such as a personal computer is used. As the I / F circuit 23, an IEEE 1394 interface may be employed in addition to the USB interface, and a serial interface or a parallel interface may be employed although the data transfer speed is reduced.

  FIG. 2 is a block circuit diagram showing an electrical configuration of the ultrasonic inspection apparatus 1.

  As shown in FIG. 2, the rotor control circuit 21 in the ultrasonic probe unit 2 is connected to the rotor units 13 and 14, and the drive control signal output from the personal computer 3 is transmitted via the I / F circuit 23. Then, the rotor units 13 and 14 are driven based on the drive control signal to rotate the transducer 12 together with the rotor units 13 and 14. Specifically, the rotor control circuit 21 rotates the first rotor unit 13 at a predetermined rotation speed, and each time the first rotor unit 13 rotates halfway (rotates 180 °), the second rotor unit 14 rotates at a predetermined angle. Just rotate. As a result, the ultrasonic irradiation point is two-dimensionally scanned along the outer surface of the probe case 11 (that is, the surface of the skin that is a living tissue).

  The signal processing circuit 22 includes a transmission circuit 24, a reception circuit 25, a transmission / reception wave separation circuit 26, a detection circuit 27, and an A / D conversion circuit 28.

  The transmission circuit 24 is a circuit that generates a pulse for driving the transducer 12, and includes a trigger circuit 24a and a pulse generation circuit 24b. In the transmission circuit 24, the trigger circuit 24a takes in a control signal output from the personal computer 3 via the I / F circuit 23, and generates a trigger signal synchronized with the rotation of the first rotor unit 13 based on the control signal. . The pulse generation circuit 24b generates an excitation pulse in response to the trigger signal. The excitation pulse is supplied to the transducer 12 via the transmission / reception wave separation circuit 26, and ultrasonic waves are emitted from the transducer 12. In the present embodiment, when the transducer 12 moves into the scanning range on the distal end side of the probe case 11 due to the rotation of the first rotor section 13, a trigger signal is generated based on the control signal, and within the scanning range. Ultrasonic waves are emitted only at.

  The transducer 12 according to the present embodiment is an ultrasonic transducer that is also used for transmitting and receiving waves, and converts ultrasonic waves (reflected waves) reflected by the skin into electrical signals. The reflected wave signal is supplied to the receiving circuit 25 via the transmission / reception wave separation circuit 26. The reception circuit 25 includes a signal amplification circuit, amplifies the reflected wave signal, and outputs the amplified signal to the detection circuit 27. The detection circuit 27 includes a gate circuit, extracts a reflected wave signal from the skin, and outputs it to the A / D conversion circuit 28. The A / D conversion circuit 28 A / D converts the output signal of the detection circuit 27 and then transfers the signal to the personal computer 3 via the I / F circuit 23.

  The personal computer 3 includes a CPU 31, an I / F circuit 32, a fast Fourier transform circuit 33, a memory 34, a storage device 35, an input device 36, and a display device 37, which are connected to each other via a bus 38.

  The CPU 31 executes a control program using the memory 34 and controls the entire apparatus in an integrated manner. The control program includes a program for controlling two-dimensional scanning by the rotor units 13 and 14, a program for calculating acoustic impedance, and the like.

  The I / F circuit 32 is an interface (specifically, a USB interface) for transmitting and receiving signals to and from the ultrasonic probe unit 2. Control signals (the rotor control circuit 21 and the rotor control circuit 21 and the like) are sent to the ultrasonic probe unit 2. Control signal to the transmission circuit 24) or transfer data (data transferred from the A / D conversion circuit 28 via the I / F circuit 23) from the ultrasonic probe unit 2 is input.

  The fast Fourier transform circuit 33 performs a Fourier transform process to obtain a frequency component of the reflected wave signal. The display device 37 is, for example, a color display such as an LCD or a CRT, and is used to display an acoustic impedance image or an input screen for various settings. The input device 36 is a keyboard, a mouse device, or the like, and is used for inputting requests, instructions, and parameters from the user.

  The storage device 35 is a magnetic disk device or an optical disk device, and the storage device 35 stores a control program and various data. The CPU 31 transfers programs and data from the storage device 35 to the memory 34 in accordance with instructions from the input device 36, and executes them sequentially. Note that the program executed by the CPU 31 may be a program stored in a storage medium such as a memory card, a flexible disk, or an optical disk, or a program downloaded via a communication medium. To do.

  Next, a skin inspection method in the present embodiment will be described.

  As shown in FIG. 3, the skin 39 is composed of an epidermis 40, a dermis 41, and a subcutaneous tissue 42 from the surface side. The epidermis 40 is on the outermost side of the skin 39 and includes a stratum corneum 43 for keeping the moisture of the skin. Generally, the thickness of the epidermis 40 is about 100 μm, and the thickness of the stratum corneum 43 is about 20 μm. Further, when the epidermis 40 and dermis 41 are combined, the thickness is about 0.4 mm to 1.4 mm. That is, the skin 39 has a layer structure in which the thickness of each layer increases in order from the surface toward the inside.

  When irradiating the skin 39 with an ultrasonic wave So containing a broadband (several MHz to several hundred MHz) frequency component from the surface side, the high frequency ultrasonic wave having a wavelength shorter than the thickness of the stratum corneum 43 of the epidermis 40. So is reflected by the stratum corneum 43. The ultrasonic wave So having a wavelength longer than the thickness of the stratum corneum 43 is transmitted through the stratum corneum 43. Among the ultrasonic waves So transmitted through the stratum corneum 43, the ultrasonic waves So having a wavelength shorter than the thickness of the epidermis 40 are reflected by the epidermis 40, and the ultrasonic waves So having a wavelength longer than the thickness of the epidermis 40 are transmitted through the epidermis 40. Further, among the ultrasonic waves So transmitted through the epidermis 40, an ultrasonic wave So having a wavelength shorter than the thickness of the dermis 41 is reflected by the dermis 41, and an ultrasonic wave So having a wavelength longer than the thickness of the dermis 41 transmits the dermis 41. .

  Therefore, it is possible to acquire information on the thickness direction (depth direction) of the skin 39 by digitally analyzing the reflected wave from the skin 39 and extracting the frequency component of the reflected wave.

  The ultrasonic inspection apparatus 1 according to the present embodiment acquires the reflected wave from the reference member 15 and the reflected wave from the skin 39, and obtains the acoustic impedance of the skin 39 for each frequency based on the reflected wave. Then, an acoustic impedance curve indicating the correlation between the frequency and the acoustic impedance is obtained, and information such as the position of the interface between layers in the skin 39 and the thickness of each layer is acquired based on the acoustic impedance curve.

  Specifically, as illustrated in FIG. 4A, the reference member 15 is irradiated with the ultrasonic wave So via the probe case 11, and the reflected wave Sr at the reference member 15 is acquired. Then, the frequency characteristic data of the intensity spectrum of the reflected wave Sr is obtained by Fourier transforming the signal of the reflected wave Sr.

  Further, as shown in FIG. 4B, the surface 39 of the skin 39 is irradiated with the ultrasonic wave So, and the reflected wave St on the skin 39 is acquired. Then, frequency characteristic data of the intensity spectrum of the reflected wave St is obtained by Fourier transforming the signal of the reflected wave St.

The relationship of the following formula (1) is established between the ultrasonic wave (incident wave) So and the reflected wave Sr irradiated at an angle orthogonal to the surface of the reference member 15.

  However, Zs is the acoustic impedance of the probe case 11, and Zr is the acoustic impedance of the reference member 15.

  Moreover, the relationship of following Formula (2) is formed between the ultrasonic wave So and the reflected wave St with an angle orthogonal to the skin 39 surface.

  Where Zt is the acoustic impedance of the skin 39.

  Accordingly, the acoustic impedance Zt of the skin 39 is obtained by the following equation (3) from the above equations (1) and (2).

  By performing the calculation of the above formula (3) for each frequency, an acoustic impedance curve as shown in FIG. 5 can be obtained.

  Here, since the ultrasonic wave having a wavelength shorter than the thickness of the stratum corneum 43 which is the uppermost layer of the skin 39 is reflected by the stratum corneum 43, the signal intensity of the reflected waves Sr and St at a high frequency corresponding to the ultrasonic wave. , The acoustic impedance Zt of the stratum corneum 43 can be obtained by the calculation of the above formula (3).

  Further, since the low-frequency ultrasonic wave passes through the stratum corneum 43 and reaches the underlying skin 40, the calculated acoustic impedance Zt of the stratum corneum 43 and the signal strengths of the reflected waves Sr and St at low frequencies are used. The acoustic impedance Zt of the skin 40 is obtained. Similarly, the acoustic impedance Zt of the dermis 41 is obtained using the calculated acoustic impedance Zt of the skin 40 and the signal strengths of the reflected waves Sr and St at low frequencies.

  Thus, the acoustic impedance curve of FIG. 5 is calculated | required by calculating | requiring the acoustic impedance Zt from the high frequency side, and calculating | requiring the acoustic impedance Zt of the low frequency side using it. And the health state of the skin 39 can be determined using the data of this acoustic impedance curve.

  That is, the slope (change rate) of the acoustic impedance curve is obtained by differentiating the equation representing the acoustic impedance curve. Then, as shown in FIG. 6, the frequencies f1, f2, and f3 are determined at locations where the slope in the acoustic impedance curve is larger than a predetermined threshold th. And at the depth corresponding to these frequencies f1, f2, and f3, the rate of change of the acoustic impedance is large, and it is estimated that the layer interface exists at that position. Therefore, the position of the interface and the thickness of each layer are determined based on these frequencies f1, f2, and f3.

  In addition, with respect to the determined frequency, the acoustic impedance on the high frequency side is the acoustic impedance on the upper layer side of the interface, and the acoustic impedance on the low frequency side is the acoustic impedance on the lower layer side of the interface. Accordingly, by obtaining these acoustic impedances, the hardness information of different layers can be obtained.

  Furthermore, in the present embodiment, by performing two-dimensional scanning of the ultrasonic irradiation point, in addition to the information on the depth direction of the skin 39 as described above, information on the plane direction of the skin 39 is acquired. A three-dimensional inspection is performed.

  In the present embodiment, the acoustic impedance Zs of the probe case 11 and the acoustic impedance Zr of the reference member 15 are stored in advance in the storage device 35 as control program data. Further, as indicated by the above formula (2), when the acoustic impedance Zs of the probe case 11 is equal to the acoustic impedance Zt of the skin 39, the ultrasonic wave is not reflected on the surface of the skin 39. Therefore, the material for the probe case 11 may be selected in consideration of the acoustic impedance Zt of the skin 39. For example, a material whose acoustic impedance Zs is about three times that of the skin 39 is used. In addition, since reflection of ultrasonic waves also occurs on the inner surface side of the probe case 11 that is an interface with the ultrasonic transmission medium W, the material of the probe case 11 can be selected in consideration of the acoustic impedance of the ultrasonic transmission medium W. preferable.

  Next, a processing example executed by the CPU 31 to inspect the skin 39 in the present embodiment will be described with reference to the flowchart of FIG.

  First, the CPU 31 outputs a control signal to the rotor control circuit 21 to drive the first rotor unit 13 and the second rotor unit 14. As a result, the ultrasound irradiation point moves so as to be positioned on the reference member 15. At this time, when the excitation pulse is supplied to the transducer 12, as shown in FIG. 4A, the reference member 15 is irradiated with the ultrasonic wave So, and the signal of the reflected wave Sr (reflected wave signal) is detected. 27. The CPU 31 takes in the digital data converted by the A / D conversion circuit 28 via the I / F circuits 23 and 32 and inputs the digital data to the fast Fourier transform circuit 33. In the fast Fourier transform circuit 33, the reflected wave signal is Fourier transformed to generate frequency characteristic data of the intensity spectrum. The CPU 31 temporarily stores the frequency characteristic data after the Fourier transform output from the fast Fourier transform circuit 33 in the memory 34 as data of the reference member 15 (step 100).

  Thereafter, the rotor control circuit 21 that has received an instruction from the CPU 31 drives each of the rotor units 13 and 14, and two-dimensional scanning of ultrasonic waves is started. CPU31 judges the rotation position of each rotor part 13 and 14, and acquires the coordinate data of a measurement point based on it (step 110).

  Then, as shown in FIG. 4 (b), the ultrasonic wave So is irradiated on the surface of the skin 39, and the reflected wave St is detected by the detection circuit 27. The CPU 31 inputs the digital data converted by the A / D conversion circuit 28 to the fast Fourier transform circuit 33, and uses the Fourier transform frequency characteristic data output from the fast Fourier transform circuit 33 as the skin 39 data as a measurement point. The data is temporarily stored in the memory 34 in association with the coordinate data (step 120).

  Thereafter, the CPU 31 uses the acquired intensity spectrum data of the reflected waves Sr and St on the reference member 15 and the skin 39 and the acoustic impedances Zr and Zs of the reference member 15 and the probe case 11 to obtain the above formula (3 ) To calculate the acoustic impedance Zt at the measurement point (step 130). Here, the acoustic impedance Zt is obtained for each frequency, and data corresponding to the acoustic impedance curve of FIG. 5 is obtained. Then, the CPU 31 stores the calculated acoustic impedance data in the memory 34 in association with the coordinate data of the measurement point.

  Thereafter, the CPU 31 performs image processing for generating an acoustic impedance image of the skin surface based on the calculated acoustic impedance Zt (step 140). As described above, ultrasonic waves on the high frequency side are reflected on the skin surface, whereas ultrasonic waves on the low frequency side are transmitted through the stratum corneum 43 on the skin surface and reflected inside the skin 39. That is, since the acoustic impedance on the low frequency side includes the hardness information inside the skin, the processing in step 140 is performed using the data on the high frequency side including only the hardness information on the skin surface. In this process, the CPU 31 performs color modulation processing using the high-frequency acoustic impedance Zt, generates image data corresponding to the magnitude of the acoustic impedance Zt, and stores the image data in the memory 34.

  The CPU 31 determines whether or not the processing at all measurement points has been completed and image data for one screen has been acquired (step 150). If all the data has not been acquired, the CPU 31 returns to step 110 and repeatedly executes the processing of steps 110 to 150. If all the data has been acquired, the CPU 31 transfers the data to the display device 37. Then, an acoustic impedance image corresponding to the data is displayed (step 160).

  By this processing, an acoustic impedance image that is color-coded according to the magnitude of the acoustic impedance on the skin 39 surface is displayed, and the acoustic impedance distribution on the skin 39 surface is confirmed by the acoustic impedance image.

  Here, when the user who has confirmed the acoustic impedance image operates the input device 36 and designates a predetermined point (coordinates) in the acoustic impedance image, the CPU 31 performs display processing for displaying information in the depth direction of the point. (Step 170). In this process, the CPU 31 first reads out frequency characteristic data corresponding to the coordinate data of a predetermined point from the memory 34. Then, the CPU 31 performs a differentiation process using the data to calculate the slope of the acoustic impedance curve, and the frequency (f1, f2, in FIG. 6) where the calculated value is larger than the predetermined threshold th. Determine f3). Then, the CPU 31 obtains the thickness of each layer (the stratum corneum 43, the epidermis 40, the dermis 41, etc.) constituting the skin 39 based on the determined frequency, and according to the thickness and the magnitude of the acoustic impedance in each layer. The hardness information and the like are displayed on the screen of the display device 37. The display mode of such hardness information is not particularly limited, and for example, the hardness may be displayed as a numerical value. Or you may display according to a color according to the grade of hardness. Note that the graphs of FIGS. 5 and 6 may be displayed on the screen of the display device 37 as necessary.

  Here, when the user designates another point (coordinates) in the acoustic impedance image again, the CPU 31 repeatedly performs display processing for displaying information in the depth direction of the point.

  An end button for instructing the end of the display process is displayed on the screen of the display device 37. When the user operates the input device 36 and presses the end button, the processing in FIG. 7 ends.

  Therefore, according to the present embodiment, the following effects can be obtained.

  (1) In the ultrasonic inspection apparatus 1 of the present embodiment, the ultrasonic wave irradiated by the transducer 12 includes a wideband frequency component. Then, by performing digital analysis (Fourier transform) on the obtained reflected wave signal, an acoustic impedance for each frequency within a wide band is obtained. In this case, it is not necessary to switch to ultrasonic waves having different frequencies and perform measurement a plurality of times as in the prior art, and an acoustic impedance curve (frequency characteristic data) can be obtained by a single ultrasonic irradiation. Since the acoustic impedance measured here is a parameter that increases in accordance with the hardness of the skin 39, the hardness information of each layer in the skin 39 can be acquired by using the frequency characteristic data. Therefore, based on this information, the health condition of the skin 39 can be inspected quickly and accurately. In addition, since the ultrasonic inspection apparatus 1 according to the present embodiment is configured to generate ultrasonic waves including different frequency components by pulse excitation, the circuit configuration such as the pulse generation circuit 24b is simplified as compared with the prior art. be able to. As a result of the simplification of the device, it is possible to reduce the cost of the device.

  (2) In the ultrasonic inspection apparatus 1 according to the present embodiment, the slope is obtained by differentiating the acoustic impedance curve, and the location on the skin 39 is determined by determining the location where the slope is greater than a predetermined threshold value. Information in the depth direction (thickness and hardness of each layer) can be obtained.

  (3) In the ultrasonic inspection apparatus 1 of the present embodiment, since the ultrasonic irradiation point is two-dimensionally scanned, information on the surface of the skin 39 can be acquired in addition to information on the depth direction of the skin 39. The skin 39 can be examined more accurately. In addition, since the ultrasonic wave that converges with the surface layer portion of the skin 39 as a focal point is used as a probe, it is possible to grasp the fine structure of the surface layer portion of the skin 39. For example, even if a micron-order hardened part exists in a layer inside the stratum corneum 43, it is possible to reliably find the hardened part.

  (4) At the time of actual inspection, there is a high possibility that the intensity of the ultrasonic wave output from the transducer 12 will fluctuate due to factors such as temperature changes and changes in circuit characteristics of the measurement system. Considering this, the ultrasonic inspection apparatus 1 of the present embodiment is provided with the reference member 15 on the outer surface of the probe case 11. Therefore, as shown in FIG. 4A, the signal of the reflected wave Sr of the reference member 15 is detected, and the acoustic impedance is calculated based on the reflected wave signal, so that correction is performed according to the variation of the measurement condition. Can do. Thereby, an accurate acoustic impedance can be obtained and the skin 39 can be accurately inspected. Further, since the reference member 15 is provided within the scanning range, the reflected wave of the skin 39 can be measured quickly following the measurement of the reflected wave from the reference member 15.

(5) Since the ultrasonic inspection apparatus 1 of the present embodiment includes the ultrasonic probe unit 2 that can be grasped by hand, the ultrasonic probe unit 2 is used to inspect the skin 39 at various locations on the body. Can do.
[Second Embodiment]

  Next, a second embodiment embodying the present invention will be described with reference to FIG.

  The ultrasonic inspection apparatus 51 in the second embodiment is an apparatus that measures the acoustic impedance of the skin using the ultrasonic microscope 52, and the personal computer 3 for controlling the ultrasonic microscope 52 and the ultrasonic microscope 52. It consists of and.

  The ultrasonic microscope 52 of the present embodiment includes a transducer 12, an I / F circuit 23, a transmission circuit 24, a reception circuit 25, a transmission / reception wave separation circuit 26, a detection circuit 27, and an A / D conversion circuit. 28, an XY stage 54, an encoder (ENC) 55, a controller 56, and drive motors 57X and 57Y are provided. In the ultrasonic microscope 52, the I / F circuit 23, the transmission circuit 24, the reception circuit 25, the transmission / reception wave separation circuit 26, the detection circuit 27, and the A / D conversion circuit 28 are the circuits of the first embodiment. It is the structure similar to 23-28. Hereinafter, the difference from the first embodiment will be mainly described.

  In the ultrasonic microscope 52, the transducer 12 for irradiating ultrasonic waves is fixed to the lower surface of the XY stage 54. The XY stage 54 includes stages 54X and 54Y for moving the ultrasonic irradiation point two-dimensionally, and motors 57X and 57Y for driving the stages 54X and 54Y, respectively. Stepping motors and linear motors are used as these motors 57X and 57Y.

  A controller 56 is connected to each of the motors 57X and 57Y, and the motors 57X and 57Y are driven in response to a drive signal of the controller 56. By driving these motors 57X and 57Y, the X stage 54X is continuously scanned (continuous feed), and the Y stage 54Y is controlled to be intermittently fed, so that the XY stage 54 can be scanned at high speed. .

  In the present embodiment, an encoder 55 is provided corresponding to the X stage 54X, and the encoder 55 detects the scanning position of the X stage 54X. Specifically, when the scan range is divided into 300 × 300 measurement points (pixels), ultrasonic waves are irradiated 300 times during one scan in the X direction (horizontal direction). Then, the position of each measurement point is detected by the encoder 55 and taken into the personal computer 3 via the I / F circuit 23. The personal computer 3 generates a drive control signal in synchronization with the output of the encoder 55 and supplies the drive control signal to the controller 56 via the I / F circuit 23. The controller 56 drives the motor 57X based on this drive control signal. Further, the controller 56 drives the motor 57Y when the scanning of one line in the X direction is completed based on the output signal of the encoder 55, and moves the Y stage 54Y by one pixel in the Y direction.

  Further, the controller 56 supplies a signal synchronized with the drive control signal to the trigger circuit 24 a of the transmission circuit 24. Accordingly, the trigger circuit 24a generates a trigger signal synchronized with the drive control signal, and the pulse generation circuit 24b generates an excitation pulse in response to the trigger signal. As a result of the excitation pulse being supplied to the transducer 12 via the transmission / reception wave separation circuit 26, ultrasonic waves are emitted from the transducer 12.

  A skin test plate 58 is provided below the transducer 12. The ultrasonic waves irradiated by the transducer 12 converge in a conical shape via the ultrasonic transmission medium W, and are focused near the lower surface of the skin examination plate 58 (that is, the surface layer portion of the skin).

  Similar to the probe case 11 in the first embodiment, the skin test plate 58 is made of a material (for example, acrylic resin) that has a known acoustic impedance different from that of a living tissue and can transmit ultrasonic waves. Is formed. In this skin test plate, a reference member 59 made of, for example, an epoxy resin is provided in a range where the ultrasonic irradiation point is scanned.

  In the present embodiment, the skin such as the arm of the examinee is brought into contact with the lower surface of the skin test plate 58, and in this state, ultrasonic waves are irradiated toward the skin. The ultrasonic wave reflected from the skin is converted into an electric signal by the transducer 12 and supplied to the detection circuit 27 through the transmission / reception wave separation circuit 26 and the reception circuit 25. Then, after the reflected wave signal from the skin is extracted in the detection circuit 27, it is transferred to the personal computer 3 via the A / D conversion circuit 28 and the I / F circuit 23.

  The personal computer 3 has the same circuit configuration (CPU 31, I / F circuit 32, fast Fourier transform circuit 33, memory 34, storage device 35, input device 36, and display device 37) as in the first embodiment. The personal computer 3 according to the present embodiment also displays the acoustic impedance image of the skin surface and the skin depth information by performing the same processing as the flowchart shown in FIG.

  Therefore, even when the ultrasonic inspection apparatus 51 is configured using the ultrasonic microscope 52 as in the present embodiment, the same effects as the effects (1) to (4) of the first embodiment can be obtained. Can do.

  In addition, you may change each embodiment of this invention as follows.

  In each of the above embodiments, the acoustic impedance image on the surface of the skin 39 (the stratum corneum 43) is displayed using the calculated acoustic impedance on the high frequency side, but the acoustic impedance on the low frequency side is used. The acoustic impedance image inside the skin 39 (the epidermis 40, the dermis 41, the subcutaneous tissue 42, etc.) may be displayed. As a specific method, first, the user confirms the thickness of each layer (skin layer 43, epidermis 40, dermis 41, etc.) of the skin 39 displayed on the screen of the display device 37, and the position (surface) of the layer to be displayed. (Depth from). Thereby, the CPU 31 reads out the acoustic impedance of the frequency corresponding to the designated position from the memory 34, performs image generation processing, and transfers the obtained image data to the display device 37, whereby the acoustic impedance image corresponding to the designated position is obtained. Is displayed.

  In each of the above embodiments, the acoustic impedance image on the surface of the skin 39 is displayed. However, an acoustic impedance image of the cross section of the skin 39 may be displayed. For example, in a state where the acoustic impedance image of the surface of the skin 39 is displayed on the screen of the display device 37, the user designates two points for setting the position of the cross section in the acoustic impedance image. The CPU 31 extracts a plurality of measurement points on a straight line connecting two specified points, reads out the frequency characteristic data of the acoustic impedance corresponding to the coordinates of each measurement point from the memory 34, and obtains the acoustic impedance in the depth direction. . Then, the CPU 31 performs image generation processing using the acoustic impedance, and transfers the image data obtained thereby to the display device 37, thereby displaying an acoustic impedance image showing a cross section at the designated position.

  Further, a predetermined area designated by the user may be configured to obtain the acoustic impedance in the depth direction using frequency characteristic data at each measurement point and display a three-dimensional acoustic impedance image of the skin 39. Good. In this way, three-dimensional information of the skin 39 can be acquired.

  In each of the above-described embodiments, the thickness and hardness of each layer of the examined skin 39 are compared with standard values, and the health state of the skin 39 according to the comparison result, for example, moist and good skin, bulkiness You may comprise so that the state of skin, such as dried skin etc., may be displayed on the screen of the display apparatus 37. FIG. Furthermore, the test result of the skin 39 is stored in the memory 34 each time, and the state change of the skin 39 is displayed on the screen of the display device 37 by comparing the previously acquired data with the data acquired this time for the same subject. It may be configured.

  The ultrasonic inspection apparatuses 1 and 51 of the above embodiments have a function of two-dimensionally scanning the ultrasonic irradiation point and obtain an acoustic impedance image of the skin 39, but this function is omitted. May be. That is, any ultrasonic inspection apparatus may be used as long as it can obtain information on the depth direction of the skin 39. For example, the thickness and hardness of the skin 39 may be inspected based on an acoustic impedance curve obtained from the reflected wave by irradiating only a predetermined measurement point with pulse-excited ultrasonic waves without performing two-dimensional scanning. . In this case, the two-dimensional scanning means (the first rotor unit 13, the second rotor unit 14, the XY stage 54, etc.) can be omitted, and the configuration of the ultrasonic inspection apparatuses 1 and 51 is simplified and manufactured. Cost can be reduced.

  In the first embodiment, the reflected wave Sr at the reference member 15 is detected at the start of scanning. However, the present invention is not limited to this. For example, every time the acoustic impedance of one scanning line on the skin 39 is measured, the reflected wave Sr on the reference member 15 is detected, and the acoustic impedance may be calculated based on the reflected wave signal. . In this case, the scanning range is set so that the reference member 15 is located on both sides or one side. In this way, when the measurement condition changes abruptly, it is possible to perform correction according to the change in the measurement condition in real time. The reference member 15 does not need to be provided at the periphery of the operation range, and may be provided at any position in the scanning range.

  In each of the above embodiments, the ultrasonic inspection apparatus 1 is configured using the personal computer 3, but a computer such as a workstation may be used in addition to that. Of course, you may comprise an ultrasonic inspection apparatus using portable terminals, such as PDA (Personal Digital Assistant). When a portable terminal such as a PDA is used instead of the personal computer 3 in the first embodiment, it is practically preferable because it can be moved with the ultrasonic probe unit 2 by hand.

  In each of the above embodiments, the skin 39 is inspected using the ultrasonic inspection apparatuses 1 and 51. However, in addition to this, a biological tissue having a layer structure may be inspected. For example, when the nail inspection is performed using the ultrasonic inspection apparatus 1, the thickness and hardness of the nail can be easily measured, and the nail health state can be appropriately determined. Further, not only biological tissues exposed on the body surface such as the skin 39 and nails, but also biological tissues not exposed on the body surface (for example, muscles and organs) are examined by the devices 1 and 51. You may go.

  Depending on the thickness of the layer structure of the biological tissue to be examined, an ultrasonic wave including a wider frequency component is required, and one type of transducer 12 may not be able to irradiate ultrasonic waves in that frequency band. In such a case, a plurality of transducers dedicated to each frequency band are provided and used by switching them. Specifically, in the first embodiment, one of the two transducers 12 provided in the first rotor unit 13 is a low-frequency transducer and the other is a high-frequency transducer.

In the ultrasonic inspection apparatuses 1 and 51 of the above-described embodiment, the color-modulated acoustic impedance image is obtained and visualized. However, the luminance-modulated acoustic impedance image may be obtained and visualized.
Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the respective embodiments described above are listed below.

  (1) In any one of claims 1 to 5, the reflected wave signal is Fourier transformed to generate frequency characteristic data of an intensity spectrum, and an acoustic impedance for a different frequency is calculated based on the data. Ultrasonic inspection method characterized by.

  (2) The ultrasonic inspection method according to any one of claims 1 to 5, wherein the layers constituting the living tissue are sequentially thickened from the surface toward the inside.

  (3) The ultrasonic examination according to claim 5, further comprising a step of determining the health state of the skin based on the thickness and hardness information of each layer in the skin and displaying the determination result on a display device. Method.

  (4) In claim 5, the thickness and hardness information of each layer in the skin is determined by comparing the data acquired last time with the data acquired this time, and the determination result is displayed on the display device. An ultrasonic inspection method comprising the step of displaying.

  (5) The ultrasonic examination apparatus according to claim 7, further comprising a display device for displaying an image of a living tissue corresponding to hardness information based on the image data generated by the image generation means.

1 is a schematic configuration diagram showing an ultrasonic inspection apparatus according to a first embodiment that embodies the present invention. The block circuit diagram which shows the electric constitution of an ultrasonic inspection apparatus. Explanatory drawing which shows reflection of the ultrasonic wave in skin. (A), (b) is explanatory drawing for demonstrating the reflection by a reference member and skin. The graph which shows an acoustic impedance curve. The graph which shows the inclination of the acoustic impedance curve of FIG. The flowchart which shows the process for test | inspecting skin. The block circuit diagram which shows the electric constitution of the ultrasonic inspection apparatus in 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,51 ... Ultrasonic inspection apparatus 12 ... Transducer as ultrasonic transducer | transducer 13,14 ... The 1st rotor part and 2nd rotor part 31 which comprise a two-dimensional scanning means 31 ... CPU as a calculation means and an image generation means
39 ... Skin as biological tissue 54 ... XY stage as two-dimensional scanning means

Claims (8)

An ultrasonic inspection method for irradiating a living tissue having a layer structure with ultrasonic waves and inspecting the living tissue based on the obtained reflected wave,
A first step of irradiating the living tissue with ultrasonic waves that are pulse-excited and include different frequency components;
A second step of obtaining hardness information at different depths in the biological tissue by calculating acoustic impedance for different frequencies based on the reflected wave from the biological tissue, and in the second step, An acoustic impedance curve indicating the correlation between frequency and acoustic impedance is obtained by calculation, and it is determined that there is a layer interface at a depth corresponding to the frequency at a location where the slope is larger than a predetermined value in the acoustic impedance curve, An ultrasonic inspection method characterized by determining the thickness of each layer . 2. The ultrasonic wave according to claim 1, wherein, in the second step, the hardness of different layers is obtained by obtaining acoustic impedances on the low frequency side and the high frequency side with the frequency of the part interposed therebetween, respectively. Inspection method. An ultrasonic inspection method for irradiating a living tissue having a layer structure with ultrasonic waves and inspecting the living tissue based on the obtained reflected wave,
  A first step of irradiating the living tissue with ultrasonic waves that are pulse-excited and include different frequency components;
  A second step of obtaining hardness information at different depths in the biological tissue by calculating acoustic impedance for different frequencies based on the reflected wave from the biological tissue;
In the second step, an acoustic impedance curve indicating a correlation between the frequency and the acoustic impedance is obtained by calculation, and a layer is formed at a depth corresponding to the frequency at a location where the slope is larger than a predetermined value in the acoustic impedance curve. And determine the hardness of the different layers by determining the acoustic impedance on the low frequency side and the high frequency side with the frequency of the above part interposed therebetween, respectively.
An ultrasonic inspection method characterized by the above.   In the first step, ultrasonic waves that are pulse-excited and include different frequency components and converge with the surface layer portion of the biological tissue as a focal point are irradiated toward the biological tissue while two-dimensionally scanning. The ultrasonic inspection method according to any one of claims 1 to 3.   The ultrasonic inspection method according to claim 1, wherein the biological tissue is skin. The ultrasonic wave for performing the method according to any one of claims 1 to 3 in irradiating ultrasonic waves to a biological tissue having a layer structure and inspecting the biological tissue based on the obtained reflected wave. An inspection device,
An ultrasonic transducer that is pulse-excited and that irradiates the biological tissue with different frequency components, receives a reflected wave from the biological tissue, and converts it into an electrical signal;
An ultrasonic examination apparatus comprising: a calculation unit that calculates hardness information at different depths in the biological tissue by calculating acoustic impedances at different frequencies based on reflected waves from the biological tissue. .   The ultrasonic inspection apparatus according to claim 6, further comprising image generation means for performing processing for generating image data indicating hardness information at different depths in the living tissue.   The apparatus further comprises a two-dimensional scanning means for two-dimensionally scanning the ultrasonic irradiation point along the surface of the biological tissue, and the ultrasonic transducer converges the ultrasonic wave with the surface layer portion of the biological tissue as a focal point. The ultrasonic inspection apparatus according to claim 6, wherein the ultrasonic inspection apparatus has a function of performing irradiation.

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