JP4830100B2 - Inspected object measuring method and inspected object measuring apparatus - Google Patents

Description

  The present invention relates to an inspection object measuring method for measuring an inspection object using ultrasonic waves, and an inspection object measuring apparatus.

  The size of the site to be excised during surgery should be kept as small as possible considering the burden on the patient after surgery. However, if part of the affected area remains without being excised, there is a problem that the disease will recur. is there. For this reason, it is necessary to sample a specimen (living tissue) from the remaining portion after excision to confirm that the affected area does not spread. Currently, this operation is performed by staining a section of the extracted biological tissue and observing it with an optical microscope. Histologically confirmed diagnosis is a diagnosis that confirms that the affected area has not spread in the specimen based on pathological findings, but it is used for postoperative confirmation because it takes several days to stain the section. .

  During the operation, it is required to determine in a short time that no affected area remains before suturing. For this reason, a method such as “tissue rapid diagnosis” in which a special dye is used for staining in a short time to confirm that the affected area has not spread in the specimen portion has been put into practical use. However, this rapid tissue diagnosis also takes about one hour, and the operation is interrupted during this time. Therefore, as an alternative method, observation of a sound velocity image using ultrasonic waves has been proposed. That is, when a sound velocity image is obtained by ultrasonic waves, it is possible to observe a living tissue without using a staining method. For this reason, the development of products using an ultrasonic microscope as a diagnostic apparatus for performing a tissue definitive diagnosis is in progress.

  Specifically, in a conventional ultrasonic microscope, the properties of a living tissue are observed by using a single-frequency burst wave and analyzing the intensity and phase of the reflected ultrasonic signal. However, such an ultrasonic microscope has a problem that it takes a long time to measure an ultrasonic signal. In addition, since an analog system such as an oscillator and a measurement system having sufficient accuracy and stability is required, there is a problem that the apparatus becomes large and complicated.

As means for solving these problems and enabling intraoperative diagnosis, the present inventors have already proposed a pulse excitation type ultrasonic microscope (see, for example, Non-Patent Document 1 and Patent Document 1). In observation using this pulse excitation type ultrasonic microscope, the tissue is cut out from a living tissue, a frozen section 51 having a thickness of several μm is prepared using the tissue, and is first fixed on a glass substrate 52 (see FIG. 15). . Then, to excite the transducer 53 by a pulse wave to output a ultrasonic wave S _0, irradiates the ultrasonic waves S ₀ to frozen sections 51 via the medium 54, such as water. The combined wave of the reflected wave S _front on the tissue surface and the reflected wave S _rear on the tissue back surface is received by the transducer 53. Further, the received wave is Fourier-transformed and compared with direct reflection from the substrate 52 to obtain an intensity and phase spectrum.

By the way, in the conventional method using a burst wave, it is necessary to measure the frequency by switching the frequency at the same measurement point and observe the interference between the reflection on the tissue surface and the reflection on the back surface. On the other hand, the pulse excitation type ultrasonic microscope has an advantage that it can be calculated by one measurement. If the frequency of the signal intensity minimum or maximum point obtained by this measurement is f _m and the phase at that time is φ _m , the reflection from the tissue surface and the back surface is the opposite phase at the minimum point and the same phase at the maximum point. Become. That is, at the minimum point, the reflection from the tissue surface is advanced in phase by (2n−1) π from the reflection from the back surface, and becomes φ _m + (2n−1) π (n is a natural number). Therefore, when the thickness of the tissue is d and the sound velocity of water is C ₀ ,

Is established.

  Therefore, the tissue thickness d is obtained as in the following equation.

Further, since the phase difference between the wave that has passed the distance 2d at the tissue sound speed C and the wave that has passed at the sound speed C ₀ of water is φ _m ,

Thus, the tissue sound velocity C is obtained as in the following equation.

  Further, at the local maximum point, the phase difference between the reflection from the tissue surface and the reflection from the back surface is 2nπ, and therefore the relationship of the following equation is established.

  If this equation is used, the tissue thickness d can be obtained as in the case of the minimum point, and the sound velocity C can be obtained using the tissue thickness d.

  Thus, a two-dimensional sound velocity image is obtained by two-dimensionally scanning the ultrasonic irradiation point while measuring the tissue sound velocity C. The speed of sound C is a parameter related to the hardness of the tissue, and the properties of the frozen section 51 can be observed from the sound speed image.

Furthermore, the present inventors have also proposed an ultrasonic image inspection apparatus that displays an acoustic impedance image of a living tissue using a pulse excitation type ultrasonic microscope. In this ultrasonic image inspection apparatus, a reference member 62 is provided at a position that is the peripheral edge of the living tissue 61 within a range in which the ultrasonic wave S ₀ is scanned, and ultrasonic waves are applied to the living tissue 61 and the reference member 62 through the glass substrate 63. S ₀ is irradiated (see FIG. 16).

The relationship of the following equation (6) is established between the ultrasonic wave (incident wave) S ₀ and the reflected wave S _r irradiated at an angle orthogonal to the surface of the reference member 62.

However, Z _s is the acoustic impedance of the glass substrate 63, and Z _r is the acoustic impedance of the reference member 62.

The following relationship (7) between the ultrasonic S ₀ and a reflected wave S _t to be irradiated at an angle perpendicular to the surface in the body tissue 61 is established.

Here, Z _t is the acoustic impedance of the living tissue 61.

Therefore, the acoustic impedance Z _t of the living tissue 61 is obtained by the following equation (8) from the above equations (6) and (7).

In this ultrasonic image inspecting apparatus, by two-dimensionally scanning the irradiation point of the ultrasonic S ₀ while measuring the acoustic impedance Z _t, the acoustic impedance image of the two-dimensional can be obtained. The acoustic impedance _{Zt is} also a parameter related to the hardness of the tissue, and the properties of the living tissue 61 can be observed from the acoustic impedance image.
JP 2004-294189 A “Medical Ultrasound: Pulse Excitation Ultrasonic Sonic Microscope” (“Ultrasonic TECHNO” VOL.15 No.6 (November 11-12, 2003) (101-105 pages), published by Nihon Kogyo Shuppansha)

By the way, although the sound velocity C and the acoustic impedance _Zt are acoustic parameters related to the hardness of the living tissue, they are not physical parameters such as the bulk modulus, so that it is possible to obtain more accurate physical characteristics of the living tissue. Can not. If it is possible to acquire the same sound velocity C and the acoustic impedance of the same location in a biological tissue Z _t, them the bulk modulus of the place that can be determined using the hardness information of the living tissue by the bulk modulus Can be accurately grasped. However, in the prior art, since the apparatus for obtaining an apparatus and acoustic impedance Z _t to determine the tissue sound velocity C is required separately, installation space or increase of the apparatus, a problem equipment cost is Dari piling up occurs. In addition, since it is necessary to install a living tissue in each device and acquire each image, the living tissue must be moved between the devices. Furthermore, since it is difficult to align the observation location, there is a problem that it is difficult to quickly perform tissue diagnosis.

  The present invention has been made in view of the above problems, and its purpose is to obtain the sound speed and acoustic impedance of an object to be inspected and to use them to more accurately grasp the physical characteristics of the object to be inspected. An object of the present invention is to provide an inspection object measuring method and an inspection object measuring apparatus.

The invention according to claim 1 is a method for measuring an object to be inspected placed on a sample placing plate based on a reflected wave of an ultrasonic wave using a pulse excitation type ultrasonic microscope, A step of acquiring a reflected wave from the non-mounting surface of the inspection object on the sample mounting plate, a step of acquiring a reflected wave from the inspection object, and a reflection wave from the non-mounting surface as a reference waveform Performing a deconvolution process for correcting a reflected wave from the object to be inspected, and using the corrected reflected wave , the reflected wave on the surface of the object to be inspected and the reflected wave on the back surface of the object to be inspected are timed. Separating in the region, and analyzing the separated reflected wave on the surface of the inspection object and the reflected wave on the back surface of the inspection object in the frequency domain, respectively. of the frequency of the reflected wave and the phase corresponding thereto The calculated and phase corresponding to the frequency of the reflected wave of the back surface of the object to be inspected, and determining the speed of sound on the basis of these, the reflected wave from the non-mounting surface, the acoustic of the sample mounting plate The ultrasonic signal intensity at a specific frequency is obtained from the impedance and the acoustic impedance of the medium , the ultrasonic signal intensity at the specific frequency, the reflected wave on the surface of the inspection object, and water from an acoustic impedance, the measurement method of the object, characterized in that it comprises the steps of obtaining an acoustic impedance that corresponds to a particular frequency and its gist.

The reflected wave reflected by the inspection object has a waveform in which the reflected wave on the surface of the inspection object and the reflected wave on the back surface interfere with each other. Therefore, as in the first aspect of the invention, the reflected wave from the inspection object is corrected by performing the deconvolution process using the reflected wave from the non-mounting surface of the inspection object on the sample mounting plate. Then, the reflected wave on the surface of the inspection object and the reflected wave on the back surface are separated from the reflected wave in the time domain. Then, the sound velocity is obtained based on the phase of each separated reflected wave, and the acoustic impedance is obtained based on the signal intensity of the reflected wave. If these sound velocities and acoustic impedances are used, various physical parameters can be obtained, so that the physical characteristics of the inspection object can be accurately grasped.

  Since each reflected wave separated in the time domain also includes different frequency components, the frequency characteristics data of the signal intensity and the phase spectrum can be obtained by subjecting each reflected wave to Fourier transform. Then, based on the phase difference obtained from the frequency characteristic data of the phase spectrum, the sound speed of the inspection object can be obtained. Further, the acoustic impedance can be obtained based on the signal intensity of the reflected wave obtained from the frequency characteristic data of the intensity spectrum. In this way, since the frequency dependence of various parameters such as sound speed and acoustic impedance can be obtained, the physical characteristics of the object to be inspected can be grasped more accurately.

The gist of the invention described in claim 2 is that, in claim 1 , the density of the inspection object is obtained by dividing the acoustic impedance by the speed of sound.

The gist of the invention described in claim 3 is that, in claim 1 or 2 , the volume elastic modulus of the object to be inspected is obtained by multiplying the acoustic impedance by the sound velocity.

Since the physical parameters such as the density and the bulk modulus of the object to be inspected can be obtained using the acoustic impedance and the sound velocity as in the inventions of claims 2 and 3 , the physical characteristics of the object to be inspected can be further improved. Accurately grasp.

Invention of Claim 4 is a measuring device which measures the to-be-inspected object mounted on the sample mounting board based on the reflected wave of an ultrasonic wave using a pulse excitation type ultrasonic microscope, An ultrasonic wave is applied to the object to be inspected by pulse excitation, and an ultrasonic transducer that receives a reflected wave from the object to be inspected, and a non-mounting surface of the object to be inspected on the sample mounting plate reference waveform reflected waves, and processing means for deconvolution process of correcting the reflected waves from the object to be inspected, and the reflected wave on the surface of the inspection object by using the corrected reflected wave by said processing means a waveform separating means for separating the reflected wave of the back surface of the inspection object in the time domain, and a back surface of the reflection wave of the object to be inspected and the reflected wave of the separated surface of the inspection object by the waveform separation means each analyzed in the frequency domain, the analysis forming From the phase that corresponds to the frequency and this reflected wave on the surface of the object to be inspected, the calculated and the phase corresponding thereto and the frequency of the reflected wave of the back surface of the object to be inspected, the sound velocity on the basis of these and sound velocity calculation means for calculating, and the reflected waves from the non-mounting surface, the acoustic impedance of the specimen mounting plate, from an acoustic impedance of the medium, along with obtaining the ultrasound signal intensity at a particular frequency, Acoustic impedance calculation means for calculating an acoustic impedance corresponding to a specific frequency from the signal strength of the ultrasonic wave at the specific frequency, the reflected wave on the surface of the inspection object, and the acoustic impedance of water The gist of the measuring device for an inspection object characterized by

According to the fourth aspect of the present invention, the ultrasonic transducer is pulse-excited to irradiate the inspection object with the ultrasonic wave, and the ultrasonic transducer receives the reflected wave from the inspection object. . Then, the deconvolution processing is performed by the processing means using the reflected wave from the non-mounting surface of the inspection object on the sample mounting plate, and the reflected wave from the inspection object is corrected. In addition, the waveform separation means separates the reflected wave on the surface of the inspection object and the reflected wave on the back surface in the time domain from the corrected reflected wave. Further, the sound speed calculating means calculates the sound speed of the object to be inspected based on the phase of each reflected wave, and the acoustic impedance calculating means calculates the acoustic impedance of the object to be inspected based on the signal intensity of each reflected wave. By using these sound speeds and acoustic impedances, various physical parameters can be obtained, and the physical characteristics of the object to be inspected can be grasped more accurately. In this case, since it is not necessary to separately provide a sound velocity measuring device and an acoustic impedance measuring device as in the prior art, the installation space for the measuring device can be reduced and the equipment cost can be reduced. Furthermore, parameters such as sound speed and acoustic impedance at the same place can be easily obtained without moving the inspection object, so that the inspection object can be quickly analyzed.

As described above in detail, according to the inventions described in claims 1 to 4 , the sound speed and the acoustic impedance of the inspection object can be obtained, and the physical characteristics of the inspection object can be grasped more accurately using them.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an ultrasonic image inspection apparatus as a measuring apparatus.

  As shown in FIG. 1, the ultrasonic image inspection apparatus 1 according to the present embodiment includes a pulse excitation type ultrasonic microscope 2, an A / D board 3, and a personal computer (personal computer) 4.

  The ultrasonic microscope 2 includes a pulse generation circuit 11, a transmission / reception separation circuit 12, a reception circuit 13, a transducer 14, an XY stage 15, an encoder (ENC) 16, a controller 17, and a drive motor 18X. , 18Y.

  The transducer 14 includes a thin film piezoelectric element 14a made of zinc oxide and an acoustic lens 14b made of sapphire rod. The thin film piezoelectric element 14a vibrates by an excitation pulse generated by the pulse generation circuit 11, and ultrasonic waves in a predetermined frequency band are generated by the acoustic lens. 14b. The ultrasonic waves in the acoustic lens 14b are converged in a conical shape, and are focused on the surface of the glass substrate 20 as a sample mounting plate via a medium 19 such as water. As the transducer 14, a transducer having a diameter of 1.2 mm, a focal length of 1.5 mm, a center frequency of 80 MHz, and a bandwidth of 50 to 105 MHz (-6 dB) is used.

  Further, an XY stage 15 as a two-dimensional scanning unit is provided below the transducer 14, and a glass substrate 20 is fixed on the stage 15. A biological tissue 21 as an object to be inspected is placed on the upper surface of the glass substrate 20, and ultrasonic waves are applied to the biological tissue 21 from above. The living tissue 21 is a frozen section (living tissue section) sliced to a thickness of about several μm (usually 4 μm to 10 μm).

  The XY stage 15 includes stages 15X and 15Y for moving the living tissue 21 two-dimensionally, and motors 18X and 18Y for driving the stages 15X and 15Y. Stepping motors and linear motors are used as the motors 18X and 18Y.

  A controller 17 is connected to each of the motors 18X and 18Y, and the motors 18X and 18Y are driven in response to a drive signal of the controller 17. By driving these motors 18X and 18Y, the X stage 15X is continuously scanned (continuous feed) and the Y stage 15Y is controlled to be intermittently fed, so that the XY stage 15 can be scanned at high speed. .

  In the present embodiment, an encoder 16 is provided corresponding to the X stage 15X, and the encoder 16 detects the scanning position of the X stage 15X. Specifically, when the scan range is divided into 300 × 300 measurement points (pixels), one scan in the X direction (horizontal direction) is divided into 300. Then, the position of each measurement point is detected by the encoder 16 and taken into the personal computer 4. The personal computer 4 generates a drive control signal in synchronization with the output of the encoder 16 and supplies the drive control signal to the controller 17. The controller 17 drives the motor 18X based on this drive control signal. Further, the controller 17 drives the motor 18Y when the scanning of one line in the X direction is completed based on the output signal of the encoder 16, and moves the Y stage 15Y by one pixel in the Y direction.

  Further, the controller 17 generates a trigger signal in synchronization with the drive control signal and supplies it to the pulse generation circuit 11. As a result, the pulse generation circuit 11 generates an excitation pulse at a timing synchronized with the trigger signal. The excitation pulse is supplied to the transducer 14 via the transmission / reception wave separation circuit 12, and ultrasonic waves are emitted from the transducer 14.

  FIG. 2 is a plan view of the XY stage 15 as seen from the transducer 14 side. As shown in FIG. 2, by performing reciprocal scanning in the x direction by the X stage 15X and scanning in the y direction by the Y stage, ultrasonic waves are two-dimensionally applied to the living tissue 21 on the glass substrate 20. Scanned.

  FIG. 3 shows an example of the ultrasonic scanning range R in the present embodiment. That is, the ultrasonic scanning range R is set so as to include a portion (glass surface 20 a) where the surface of the glass substrate 20 is exposed in addition to the biological tissue 21. Then, scanning is started from the position of the upper left corner of the scanning range R, and scanning is sequentially performed two-dimensionally in the X direction and the Y direction as indicated by arrows.

  The thin film piezoelectric element 14a of the transducer 14 shown in FIG. 1 is an ultrasonic transducer that is also used for transmitting and receiving waves, and converts ultrasonic waves (reflected waves) reflected by the living tissue 21 into electrical signals. The reflected wave signal is supplied to the receiving circuit 13 via the transmission / reception wave separation circuit 12. The reception circuit 13 includes a signal amplification circuit (not shown), amplifies the reflected wave signal, and outputs the amplified signal to the detection circuit 23 of the A / D board 3.

  The detection circuit 23 is a circuit for detecting a reflected wave of an ultrasonic wave and includes a gate circuit (not shown). The detection circuit 23 of the present embodiment extracts the reflected wave signal of the glass surface 20 a or the living tissue 21 from the reflected wave signal received by the transducer 14. Since the ultrasonic wave is repeatedly reflected between the transducer 14 and the glass surface 20a or the living tissue 21, the detection circuit 23 is configured to extract a reflected wave signal obtained first. Then, the reflected wave signal extracted by the detection circuit 23 is input to the A / D conversion circuit 24, subjected to A / D conversion, and then transferred to the personal computer 4.

  The personal computer 4 includes a CPU 31, interfaces (I / F) 32 and 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 XY stage 15, a program for calculating various parameters such as sound speed and acoustic impedance, and the like.

  The interface 32 is a communication port (for example, a USB port) for taking in transfer data (such as a reflected wave signal after A / D conversion) from the A / D board 3, and the interface 33 is a drive control to the controller 17. This is an input / output port for outputting a signal and capturing an output signal of the encoder 16.

  The display device 37 is, for example, a color display such as an LCD or CRT, and is used to display an image of the living tissue 21 and 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 method for calculating various parameters such as the thickness, sound speed, acoustic impedance, etc. of the living tissue 21 in the ultrasonic image inspection apparatus 1 of the present embodiment will be described.

First, as shown in FIG. 4, on the surface (glass surface) 20a of the glass substrate 20 is irradiated with ultrasonic waves S _o, to obtain a reflected wave S _ref at the glass surface 20a. Thereafter, the surface of the body tissue 21 is irradiated with ultrasonic waves S _o, to obtain a reflected wave S _t from the living tissue 21. The reflected wave S _t from the living tissue 21 is obtained as a composite wave including reflected wave S _rear of the tissue back surface reflected wave S _front of the tissue surface. By performing the deconvolution processing as a reference waveform reflected wave S _ref in the glass surface 20a, the reflected wave of the correction to the tissue surface reflected wave S _t of the living tissue 21 S _front the tissue back surface reflected wave S Separate from _rear .

In this deconvolution process, the reflected wave S _ref, the S _t Fourier transform respectively, by dividing the frequency components of reflected wave S _t after the Fourier transform at the frequency components of reflected wave S _ref, further result of the calculation Is inverse Fourier transformed. Thus, the data of corrected reflected wave S _t is obtained.

Figure 5 illustrates a reflective wave S _t of the reflected wave S _ref and the biological tissue 21 of deconvolution Pretreatment of the glass surface 20a. Figure 6 shows the reflected wave S _t of the reflected wave S _ref and the biological tissue 21 of the glass surface after deconvolution processing.

As shown in FIGS. 5 and 6, the de reflected wave S _t of the convolution processing biological tissue 21, which is corrected by the correction before reflections separable waveform at the surface and the back surface of the body tissue 21 as compared to the waveform It becomes. In this embodiment, by applying a window function to this deconvolution process by the corrected reflected wave S _t, and a reflected wave S _rear at the tissue back surface and the reflected wave S _front at the tissue surface in the time domain To separate.

This separation was reflected waves S _front was, S _rear also contain different frequency components in the same manner as ultrasonic S _o. Therefore, it is possible to obtain the reflected waves S _front, the reflected wave by each Fourier transform data of S _rear S _front, the frequency characteristic data of the intensity and phase spectra of the S _rear (see FIGS. 7 and 8). These frequency characteristic data are data based on the reflected wave S _ref on the glass surface 20a.

Here, the phase φ _front of the reflected wave S _{front on} the tissue surface is expressed by the following equation.

Further, the phase φ _rear of the reflected wave S _rear on the tissue back surface is expressed by the following equation.

Where f is the frequency, d is the thickness of the tissue, C ₀ is the speed of sound of water, and C is the speed of sound of the tissue.

  Therefore, the thickness d of the structure is obtained from the following equation from the above equation (9).

  Further, from the above equation (10), the sound velocity C of the tissue is obtained by the following equation.

As described above, the tissue sound speed C corresponding to each frequency f can be obtained by substituting the frequency f and the phases φ _front and φ _rear according to the frequency f into the above equations (11) and (12).

Further, the reflected wave S _ref on the glass surface 20a, the reflected wave S _{front on} the tissue surface, and the reflected wave S _rear on the tissue back surface are each expressed by the following equations.

However, Z _s is the acoustic impedance of the glass substrate 20, Z _w is the acoustic impedance of water, Z _t is the acoustic impedance of the biological tissue 21, α _w is the attenuation constant of water, and α _t is the attenuation constant of the biological tissue 21.

Since the influence of the water attenuation constant α _{w on} the measurement conditions is extremely small, the incident ultrasonic wave S ₀ can be simplified as the following equation using the above equation (13).

Accordingly, the signal intensity of the ultrasonic wave S ₀ at the predetermined frequency f can be obtained using the reflected wave S _ref on the glass surface 20a, the acoustic impedance Z _s of the glass substrate 20, and the acoustic impedance Z _{w of} water. .

  Further, the acoustic impedance Zt of the living tissue 21 is expressed by the following equation using the above equation (14).

Therefore, the acoustic impedance Z _t at the predetermined frequency f can be obtained using the signal intensity of the ultrasonic wave S _{0 and} the signal intensity of the reflected wave S _{front on} the tissue surface at the frequency f. Here, the frequency characteristic data of the intensity spectrum shown in FIG. 7 is used for the reflected wave _Sfront on the tissue surface.

Further, using the acoustic impedance _Zt and the sound velocity C of the living tissue 21 calculated as described above, the density ρ and the bulk modulus K are obtained as follows.

That is, determine the density ρ of the living tissue 21 by dividing the acoustic impedance Z _t at the speed of sound C, obtaining the bulk modulus K of the living tissue 21 by multiplying the acoustic impedance Z _t and sonic C.

Furthermore, the attenuation constant α _t of the living tissue 21 is expressed as the following equation.

Thus, the attenuation constant alpha _t of the living tissue 21 is determined using the signal strength of the reflected wave S _rear of a reflective wave S _ref and tissue rear surface at the tissue thickness d and the glass surface 20a. Note that the attenuation constant α _t may be calculated based on the signal intensity of the ultrasonic wave S0 obtained by Expression (16), the acoustic impedance Z _t obtained by Expression (17), and the like.

  Next, a processing example executed by the CPU 31 to generate an image of the living tissue 21 in the present embodiment will be described with reference to the flowchart of FIG.

  First, the CPU 31 drives the motors 18X and 18Y by the controller 17 by outputting a control signal, and moves the XY stage 15 so that the ultrasonic wave irradiation point is located on the glass surface 20a. At this time, when an excitation pulse is supplied to the transducer 14, an ultrasonic wave is emitted from the transducer 14, and an electric signal of a reflected wave is extracted by the detection circuit 23. Then, the CPU 31 takes in the digital data converted by the A / D conversion circuit 24 via the interface 32, and stores the data in the memory 34 as data of a reflected wave on the glass surface 20a (step 100).

  Next, the CPU 31 drives the motors 18X and 18Y by the controller 17 by outputting a control signal, and starts two-dimensional scanning by the XY stage 15. At this time, the CPU 31 acquires coordinate data of the measurement point based on the output of the encoder 16 (step 110). Here, when an excitation pulse is supplied to the transducer 14, ultrasonic waves are emitted from the transducer 14, and an electric signal of a reflected wave is extracted by the detection circuit 23. Then, the CPU 31 takes in the digital data converted by the A / D conversion circuit 24 through the interface 32, and stores the data in the memory 34 in association with the coordinate data as reflected wave data at each measurement point (step). 120).

  Thereafter, the CPU 31 as the processing means performs a deconvolution process using the data of the reflected wave from the glass surface 20a (step 130). FIG. 10 shows a specific example of the deconvolution process.

That is, the CPU 31 as the first Fourier transform means performs Fourier transform on the data of the reflected wave S _ref from the glass surface 20a (step 131). Then, CPU 31 as a second Fourier transform means, the data of the reflected wave _{S t} at the measuring points in the biological tissue 21 to Fourier transform (step 132). Then, CPU 31 of the dividing means divides the frequency components of reflected wave S _t after the Fourier transform in the frequency component of the reflected wave S _ref (step 133). Thereafter, the CPU 31 as the inverse Fourier transform means obtains the data of the reflected wave _St (see FIG. 6) corrected by performing the inverse Fourier transform on the division result (step 134). After the end of this process, the CPU 31 proceeds to step 140 shown in FIG.

In step 140, CPU 31 of the waveform separation means, using a predetermined window function, and a reflected wave S _rear from the corrected reflected wave S _t in the reflected wave S _front and tissue rear surface at the tissue surface in the time domain To separate. Next, the CPU 31 performs Fourier transform on the separated data of the reflected waves _Sfront and _Srear , respectively, and obtains frequency characteristic data of the phase spectrum of the reflected waves _Sfront and _Srear . And CPU31 as a sound speed calculation means performs the calculation corresponding to the said Formula (11) and Formula (12) using the data, The thickness d and the sound speed C of the biological tissue 21 in a measurement point are obtained. Calculation is performed for each frequency, and the calculated values are stored in the memory 34 in association with the coordinate data of each measurement point (step 150).

Thereafter, the CPU 31 as the acoustic impedance calculation means calculates the acoustic impedance Z _t of the living tissue 21 at the measurement point for each frequency by performing an operation corresponding to the above equations (16) and (17). The calculated value is stored in the memory 34 in association with the coordinate data of each measurement point. Further, by using the calculated sound velocity C, acoustic impedance _{Zt, and the} like, and performing calculations corresponding to the above formulas (18), (19), and (20), the density ρ, the bulk modulus K, the damping constant α Parameters such as _t are calculated for each frequency, and the calculated values are stored in the memory 34 in association with the coordinate data of each measurement point (step 160).

  The CPU 31 determines whether or not the processing at all measurement points has been completed and measurement data for one screen has been acquired (step 170). Here, when all the data has not been acquired, the CPU 31 returns to step 100 and repeatedly executes the processing of steps 100 to 170, and when all the data has been acquired, executes the image display processing (step S1). 180).

FIG. 11 shows a specific example of the image display process.
First, the CPU 31 transmits predetermined data to the display device 37 to display a setting screen (step 181). On this setting screen, for example, a check box for selecting the type of image to be displayed (one image such as a sound velocity image, an impedance image, a density image) and a text box for specifying a frequency are displayed. Yes. Then, the input device 36 is operated by the user, the type of image is selected by the check box, and a predetermined frequency is input to the text box. Here, for example, when a sound speed image is selected, the CPU 31 as the image generation means sequentially reads out the sound speed C data for one screen corresponding to the input frequency from the memory 34 and converts it into the sound speed C data. Based on this, image processing for generating a sound velocity image is performed (step 182). That is, the CPU 31 performs color modulation processing using the sound speed C and generates image data corresponding to the magnitude of the sound speed C. Then, the CPU 31 displays the sound velocity image 39 as shown in FIG. 12 by transferring the image data to the display device 37 (step 183). In this way, the CPU 31 ends the present process after displaying the sound velocity image 39 of the frequency designated by the user on the display device 37.

Further, in this embodiment, when an image of acoustic impedance _Zt or density ρ is selected on the setting screen displayed in step 181, an acoustic impedance image 40 as shown in FIG. 13 or as shown in FIG. A density image 41 or the like is displayed on the display device 37. Further, when a plurality of types of images are selected on the setting screen, the plurality of images are displayed side by side on the display device 37. In the images shown in FIGS. 12 to 14 (the sound velocity image 39, the acoustic impedance image 40, and the density image 41), the difference in the parameter values in the biological tissue 21 is indicated by the shading of the color. Are displayed as color images that are color-coded according to the color.

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

(1) In the ultrasonic image inspecting apparatus 1 of the present embodiment, it is possible to measure the sound velocity C and the acoustic impedance Z _t of the living tissue 21, further, by using the sound velocity C and the acoustic impedance Zt, density [rho, volume Various parameters such as the elastic modulus K and the damping constant α _t can be obtained. Further, in the present embodiment, it is possible to obtain information on the frequency dependence of the various parameters, such as sound velocity C and the acoustic impedance Z _t. Therefore, the physical characteristics of the living tissue 21 can be determined more accurately by these parameters. Specifically, for example, since the bulk modulus K is a physical parameter indicating the hardness of the living tissue 21, the hardness information of the living tissue 21 can be accurately obtained by the bulk modulus K. Moreover, since the attenuation constant α _t at a low frequency is an acoustic parameter related to the viscosity of the living tissue 21, the degree of stickiness of the living tissue 21 can be determined by the attenuation constant α _t .

(2) In the ultrasonic image inspecting apparatus 1 of this embodiment, it is not necessary to separately provide a measuring device of the sound velocity C of the measuring device and the acoustic impedance Z _t as in the prior art, it is possible to reduce the installation space , Equipment costs can be reduced. Furthermore, since the sound speed C, acoustic impedance _Zt, etc. of the same place can be easily acquired without moving the biological tissue 21, it is possible to quickly analyze the biological tissue 21.

(3) In the ultrasonic image inspection apparatus 1 of the present embodiment, the ultrasonic irradiation point is scanned two-dimensionally by the XY stage 15, so that the sound velocity C and acoustic impedance at a plurality of points in the biological tissue 21 are obtained. it can be calculated parameters such as Z _t. An image of the living tissue 21 can be generated by performing image processing using these parameters. In particular, in the present embodiment, in addition to the acoustic image such as the sound velocity image 39 and the acoustic impedance image 40, an image according to the density ρ and the bulk modulus K, which are physical parameters, can be displayed. It becomes possible to confirm the structure that cannot be.

  (4) Since the ultrasonic image inspection apparatus 1 according to the present embodiment can display a plurality of types of images such as the sound velocity image 39 and the acoustic impedance image 40 on the display device 37, the correlation between them is based on each image. Sex can be examined.

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

In the above embodiment, the thickness d and the thickness d of the living tissue 21 are corrected based on the phases φ _front and φ _rear of the reflected waves S _front and S _rear separated from the reflected wave by correcting the reflected wave by the deconvolution process. Although the sound velocity C is obtained, the present invention is not limited to this. As in the prior art, the frequency characteristics data of intensity and phase spectrum is obtained by Fourier transforming the reflected wave from the living tissue and comparing it with the reflected wave from the glass surface, and the frequency at the minimum or maximum point of the intensity spectrum. And the thickness d and sound velocity C of the living tissue may be obtained based on the phase at that frequency. Of course, determined in a separate measuring device and the thickness d and the sound velocity C and the acoustic impedance Z _t, the density ρ based on them may be obtained physical parameters, such as bulk modulus K. However, when the sound velocity C and the acoustic impedance _Zt are measured by the same device and various parameters are obtained based on the measured sound velocity C and the acoustic impedance Zt as in the ultrasonic image inspection device 1 of the above-described embodiment, The characteristics can be grasped more quickly.

In the above embodiment, after measuring the parameters such as the sound velocity C and the acoustic impedance Z _t to the living tissue 21 by irradiating ultrasonic wave S _o, to display the setting screen used to specify the type and frequency of the image However, the present invention is not limited to this. For example, a configuration screen may be displayed to designate the type and frequency of an image before measuring the sound velocity C by irradiating ultrasonic waves (before the processing of Step 100 in FIG. 9). In this way, it is only necessary to obtain parameters corresponding to the designated frequency and generate image data corresponding thereto, so that the capacity of the memory 34 to be used and the processing load on the CPU 31 can be suppressed.

  In the above embodiment, the XY stage 15 is driven to scan the ultrasonic irradiation point two-dimensionally. However, a two-dimensional scanning unit may be provided on the ultrasonic transducer 14 side. Good.

  In the above embodiment, various parameters of the living tissue 21 as the object to be inspected are measured, but other parameters such as a resin surface may be measured.

  In the above embodiment, a plurality of images such as the sound velocity image 39, the acoustic impedance image 40, and the density image 41 are displayed side by side on the display device 37. However, a plurality of images may be displayed in a superimposed manner. In this case, superimposed image data is generated by superimposing the image data corresponding to each parameter, and an image (superimposed image) is displayed on the display device 37 based on the superimposed image data. Here, for example, by superimposing the sound velocity image 39 and the acoustic impedance image 40, it is possible to generate an image according to the bulk modulus K, and the physical characteristics of the living tissue 21 can be further improved using the image. It becomes possible to grasp accurately.

  In the above embodiment, the ultrasonic image inspection apparatus 1 is configured using the personal computer 4, but a computer such as a workstation may be used instead. Further, the display device 37 for displaying images such as the sound velocity image 39, the acoustic impedance image 40, and the density image 41 is provided integrally with the personal computer 4, but may be provided separately from the personal computer 4. Good.

  In the ultrasonic image inspection apparatus 1 according to the above-described embodiment, an image obtained by color modulation is obtained. However, it may be visualized as a luminance-modulated image.

  Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the embodiment described above are listed below.

  (1) In claim 2, frequency characteristics data of a phase spectrum is obtained by performing Fourier transform on each of the separated reflected waves, and the thickness of the object to be inspected is based on a phase difference obtained from the data. And a method for measuring an object to be inspected, characterized by obtaining a sound velocity.

  (2) In claim 2, the frequency characteristic data of the intensity spectrum is obtained by performing Fourier transform on each separated reflected wave, and the acoustic impedance is obtained based on the signal intensity of the reflected wave obtained from the data. A method for measuring an object to be inspected.

  (3) In Claim 1, frequency characteristics data of intensity and phase spectrum are obtained by performing Fourier transform on the reflected wave from the inspection object and comparing it with the reflected wave from the non-mounting surface. A method for measuring an object to be inspected, wherein the thickness and sound velocity of the object to be inspected are determined based on a frequency at a minimum point or a maximum point and a phase at the frequency.

  (4) The method for measuring an inspection object according to any one of claims 1 to 4, wherein an attenuation constant is obtained based on the acoustic impedance.

  (5) In Claim 5, the processing means Fourier-transforms the first Fourier transform means for Fourier transforming the reflected wave from the non-mounting surface of the object to be inspected, and the reflected wave from the object to be inspected. Second Fourier transform means, division means for dividing the transform result obtained by the second Fourier transform means by the transform result obtained by the first Fourier transform means, and inverse Fourier transform of the division result And an inverse Fourier transform means for obtaining reflected wave data corrected thereby.

  (6) The apparatus for measuring an inspection object according to claim 5, further comprising two-dimensional scanning means for two-dimensionally scanning the ultrasonic irradiation point.

  (7) The acoustic parameter measurement device according to the technical idea (6), image generation means for performing processing for generating an image based on sound speed and acoustic impedance of the inspection object, and display for displaying the image And an ultrasonic image inspection apparatus.

  (8) The ultrasonic image inspection apparatus according to the technical idea (7), wherein the image generation unit generates image data for image display by luminance modulation or color modulation.

  (9) The ultrasonic image inspection apparatus according to the technical idea (7) or (8), wherein a plurality of images including a sound velocity image and an acoustic impedance image are separately displayed on the display device.

  (10) The ultrasonic image inspection apparatus according to (9), wherein the plurality of images are displayed side by side on the display device.

  (11) The ultrasonic image inspection apparatus according to the technical idea (9), wherein the plurality of images are superimposed and displayed on the display device.

1 is a schematic configuration diagram illustrating an ultrasonic image inspection apparatus according to an embodiment embodying the present invention. The top view of the XY stage seen from the transducer side. Explanatory drawing which shows the scanning range of an ultrasonic wave. Explanatory drawing which shows each reflected wave. Explanatory drawing which shows the reflected wave before a deconvolution process. Explanatory drawing which shows the reflected wave after a deconvolution process. The graph which shows the intensity spectrum of the reflected wave in the surface and back surface of a biological tissue. The graph which shows the phase spectrum of the reflected wave in the surface and back surface of a biological tissue. The flowchart which shows the process for producing | generating the image of a biological tissue. The flowchart which shows a deconvolution process. The flowchart which shows an image display process. Explanatory drawing which shows a sound speed image. Explanatory drawing which shows an acoustic impedance image. Explanatory drawing which shows a density image. The schematic diagram which shows the sound speed measuring method in the conventional pulse excitation type ultrasonic microscope. The schematic diagram which shows the acoustic impedance measuring method in the conventional pulse excitation type ultrasonic microscope.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ultrasonic image inspection apparatus as a measuring device 2 ... Pulse excitation type ultrasonic microscope 14a ... Thin film piezoelectric element as an ultrasonic transducer 20 ... Glass substrate as a sample mounting plate 20a ... Glass surface as a non-mounting surface DESCRIPTION OF SYMBOLS 21 ... Living tissue as a to-be-inspected object 31 ... Processing means, waveform separation means, and CPU as calculation means

Claims (4)

A method for measuring an object to be inspected placed on a sample placing plate based on a reflected wave of ultrasonic waves using a pulse excitation type ultrasonic microscope,
Obtaining a reflected wave from the non-mounting surface of the object to be inspected on the sample mounting plate;
Obtaining a reflected wave from the inspection object;
Performing a deconvolution process for correcting a reflected wave from the inspection object using a reflected wave from the non-mounting surface as a reference waveform ;
And separating the reflected wave of the back surface of the inspection object and the reflected wave on the surface of the inspection object in the time domain by using the corrected reflected waves,
Wherein the separated the back of the reflected wave of the inspection object and the reflected wave on the surface of the object to be inspected and analyzed by their respective frequency domain, from the analysis result, the frequency of the reflected wave on the surface of the object to be inspected And a phase corresponding thereto, a frequency of a reflected wave on the back surface of the object to be inspected, and a phase corresponding thereto are calculated , and a sound speed is obtained based on these ,
Wherein the reflected wave from the non-mounting surface, the acoustic impedance of the sample mounting plate, and the acoustic impedance of the medium, along with obtaining the ultrasound signal intensity at a particular frequency, at the particular frequency ultrasonic and the signal intensity of the sound wave, the reflected wave on the surface of the object to be inspected, and a water acoustic impedance, the measurement method of the object, characterized in that it comprises the steps of obtaining an acoustic impedance that corresponds to a particular frequency . The method for measuring an inspection object according to claim 1 , wherein the density of the inspection object is obtained by dividing the acoustic impedance by the speed of sound. Measurement methods of the object according to claim 1 or 2, wherein the determination of the bulk modulus of the specimen by multiplying the speed of sound and the acoustic impedance. A measurement device that measures an object to be inspected placed on a sample placing plate based on a reflected wave of an ultrasonic wave using a pulse excitation type ultrasonic microscope,
An ultrasonic transducer for irradiating the object to be inspected by pulse excitation and receiving a reflected wave from the object to be inspected;
A processing means for performing a deconvolution process for correcting a reflected wave from the inspection object , using a reflected wave from the non-mounting surface of the inspection object on the sample mounting plate as a reference waveform ;
A waveform separating means for separating the reflected wave of the back surface of the test 査物 and the reflected wave on the surface of the inspection object in the time domain by using the corrected reflected wave by said processing means,
A rear surface of the reflection wave of the reflected wave and the inspection object on the surface of the waveform separation the inspection object separated by means analyzes each frequency domain, from the analysis result morphism anti surface of the object to be inspected a phase corresponding to the frequency of the wave, the calculated and the phase that corresponds to the frequency and this reflected wave of the back surface of the object to be inspected, and sonic calculating means for calculating the speed of sound on the basis of these,
Wherein the reflected wave from the non-mounting surface, the acoustic impedance of the sample mounting plate, and the acoustic impedance of the medium, along with obtaining the ultrasound signal intensity at a particular frequency, at the particular frequency ultrasonic and the signal intensity of the sound wave, the reflected wave on the surface of the object to be inspected, and a water acoustic impedance, inspected, characterized in that it comprises an acoustic impedance calculating means for calculating an acoustic impedance that corresponds to a particular frequency Measuring device for things.