KR20130039198A - Method of producing photoacoustic image for detecting calcification tissue and producing apparatus thereof - Google Patents

Abstract

PURPOSE: A method and apparatus for generating a photoacoustic image for detecting a calcification tissue are provided to supply accurate calcification tissue information to a user by detecting a microscale calcification phenomenon in breast and thyroid gland tissues. CONSTITUTION: A laser applying unit(100) applies a laser to an object. A photoacoustic signal receiving unit(105) receives a photoacoustic signal generated after the laser is applied to the object. A calcification tissue determining unit(110) determines whether a tissue is a calcification tissue or a peripheral tissue by comparing the size of the photoacoustic signal. A photoacoustic image postprocessing unit(120) emphasizes a calcification tissue image and removes a peripheral tissue image. An ultrasonic image generating unit(130) generates an ultrasonic image by using the photoacoustic signal received from the photoacoustic signal receiving unit. [Reference numerals] (100) Laser applying unit; (105) Photoacoustic signal receiving unit; (110) Calcification tissue determining unit; (120) Photoacoustic image postprocessing unit; (130) Ultrasonic image generating unit; (140) Image output unit; (AA) Object;

Description

Method of producing photoacoustic image for detecting calcification tissue and producing apparatus

The present invention relates to a photoacoustic image generating method, and more particularly, to a photoacoustic image generating method and apparatus that can easily distinguish between calcified tissue and surrounding tissues in the body.

Calcification in breast and thyroid tissues is an important clue in the early diagnosis of cancer. That is, the microscale calcification acts as an indicator of cancer occurrence, and it is very important to detect the calcified tissue in advance.

Early diagnosis of breast and thyroid cancer is confirmed by mammography (Mammography), or ultrasound or biopsy (biopsy) to verify positive or malignant.

Looking at the drawbacks of this method, the mammography is irradiated with excessive X-rays on the human body, the pain caused by the compression to the patient, real-time imaging is difficult, especially in the thyroid gland.

On the other hand, in the case of an ultrasound image, it is a non-radiation imaging method that can provide an image in real time, and does not give patients discomfort such as compression, but the contrast is low and the image has a lot of noise. In inducing this, there was a problem that it is difficult to accurately identify the calcified tissue or lesion. Therefore, there is a need for a real-time imaging technique capable of further emphasizing the image of the microcalcified tissue and minimizing the response to the image without the calcified tissue.

Therefore, the first problem to be solved by the present invention is to provide a real-time photoacoustic image generation method that can easily distinguish between the calcified tissue and the surrounding tissue inside the body.

The second problem to be solved by the present invention is to provide an optoacoustic image generating apparatus that can distinguish between clinically meaningless calcified tissue and meaningful calcified tissue that are not observed even in mammography.

Further, the present invention provides a computer-readable recording medium having recorded thereon a program for executing the above method on a computer.

In order to achieve the first object, the present invention comprises the steps of applying a light energy having a specific wavelength to the object containing calcified tissue; Receiving an optoacoustic signal generated by the object; And generating an optoacoustic image of the calcified tissue from the received optoacoustic signal.

According to an embodiment of the present invention, when the specific wavelength is in the 680 nm to 710 nm band, the photoacoustic image of the calcified tissue by using the calcified tissue to generate a photoacoustic signal of a larger size than the surrounding biological tissue Can be generated.

According to another embodiment of the present invention, light energy having two different wavelengths may be applied to the object, and the calcified tissue may be imaged using each photoacoustic signal generated by the object.

At this time, one wavelength is present in the wavelength band of 680 nm to 710 nm, the other wavelength is preferably dependent on the light absorption coefficient of the surrounding biological tissue.

In addition, by comparing the magnitudes of the photoacoustic signals generated in the object, a peripheral image other than the calcified tissue may be removed, or the calcified tissue image may be enhanced.

According to another embodiment of the present invention, the light energy belonging to the wavelength band of 680 nm to 710 nm is applied to the object, the magnitude of the photoacoustic signal generated in the object and the light energy belonging to the 800 nm to 1000 nm wavelength band May be applied to the subject, and the calcified tissue may be classified in consideration of the ratio of the magnitude of the photoacoustic signal generated in the subject.

In addition, measuring the first photoacoustic signal for the microcalcification-active wavelength band; Measuring a second optoacoustic signal for the microcalcification-inactive wavelength band; And reinforcing the first optoacoustic signal if the first optoacoustic signal is greater than the second optoacoustic signal, and if the first optoacoustic signal is less than the second optoacoustic signal, It may include the step of removing.

In addition, measuring the first photoacoustic signal for the microcalcification-active wavelength band; Measuring a second optoacoustic signal for the microcalcification-inactive wavelength band; And comparing the first image generated from the first photoacoustic signal with the second image generated from the second photoacoustic signal, and removing the signal simultaneously and using the signal appearing only on the first image. It may include generating an image.

The present invention provides an optoacoustic signal receiving unit for receiving an optoacoustic signal generated in the object to achieve the second object; And an optoacoustic image generator for generating an optoacoustic image of the calcified tissue included in the object from the received photoacoustic signal.

In order to solve the above other technical problem, the present invention provides a computer-readable recording medium having recorded thereon a program for executing the above-mentioned photoacoustic image generating method on a computer.

According to the present invention, it is possible to easily distinguish between the calcified tissue inside the body and the surrounding tissue. In addition, according to the present invention, it is possible to distinguish between clinically meaningless calcified tissue and meaningful calcified tissue which are not observed even in mammography. Furthermore, according to the present invention, microscale calcification in breast and thyroid tissue can be detected in real time. Therefore, by providing accurate information about the microcalcified tissue to the user, more accurate needle biopsy can be induced and a false positive problem has always been a problem in early diagnosis of cancer. More sophisticated and reliable diagnosis is possible.

1 is a block diagram of a photoacoustic imaging device (PAI) according to an embodiment of the present invention.
2 is a flowchart of a photoacoustic imaging method according to an exemplary embodiment of the present invention.
3 is a detailed flowchart of steps 210 and 220 of the photoacoustic imaging method according to an exemplary embodiment of the present invention shown in FIG. 2.
4 shows the results of ex vivo experiments on biological tissue specimens.
FIG. 5 shows the magnitude of the photoacoustic signal generated according to the wavelength of the laser, and the microcalcification reaction wavelength section and the unreacted wavelength section.
6 shows the relationship between the laser wavelength and the light absorption coefficient μ _a for each tissue.
7 compares an optoacoustic image when a laser having a wavelength of 690 nm is applied to an object and an optoacoustic image when a laser having a wavelength of 800 nm is applied to an object.

Prior to the description of the specific contents of the present invention, for the convenience of understanding, the outline of the solution of the problem to be solved by the present invention or the core of the technical idea will be presented first.

Optoacoustic image generation method according to an embodiment of the present invention comprises the steps of applying a light energy having a specific wavelength to the object containing calcified tissue; Receiving an optoacoustic signal generated by the object; And generating an optoacoustic image of the calcified tissue from the received optoacoustic signal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art, however, that these examples are provided to further illustrate the present invention, and the scope of the present invention is not limited thereto.

The configuration of the invention for clarifying the solution to the problem to be solved by the present invention will be described in detail with reference to the accompanying drawings based on the preferred embodiment of the present invention, the same in the reference numerals to the components of the drawings The same reference numerals are given to the components even though they are on different drawings, and it is to be noted that in the description of the drawings, components of other drawings may be cited if necessary. In addition, in describing the operation principle of the preferred embodiment of the present invention in detail, when it is determined that the detailed description of the known function or configuration and other matters related to the present invention may unnecessarily obscure the subject matter of the present invention, The detailed description is omitted.

In addition, in the entire specification, when a part is referred to as being 'connected' to another part, it may be referred to as 'indirectly connected' not only with 'directly connected' . In the present specification, the singular form includes plural forms unless otherwise specified in the specification. As used herein, “comprises” and / or “comprising” refers to the presence of one or more other components, steps, operations and / or elements. Or does not exclude additions.

1 is a block diagram of a photoacoustic imaging device (PAI) according to an embodiment of the present invention.

Referring to FIG. 1, the optoacoustic imaging apparatus according to the present exemplary embodiment includes a laser applying unit 100, an optoacoustic signal receiver 105, an optoacoustic image generator 125, an ultrasonic image generator 130, and The image output unit 140 is configured. The optoacoustic image generator 125 includes a calcification tissue determination unit 110 and an optoacoustic image post-processing unit 120.

The laser applying unit 100 applies the laser to the object to be observed.

The optoacoustic signal receiver 105 receives an optoacoustic signal generated after the laser is applied to the object.

The calcification tissue determination unit 110 compares the magnitude of the photoacoustic signal according to the wavelength of the laser to determine whether the calcification tissue or surrounding tissue.

The optoacoustic image post-processing unit 120 emphasizes the image determined to be calcified tissue and removes the image determined to be the surrounding tissue.

The ultrasound image generator 130 generates an ultrasound image by using the photoacoustic signal received from the photoacoustic signal receiver 100.

The image output unit 140 outputs the post-processed image by the photoacoustic image post-processing unit 120 or simultaneously outputs the post-processed image and the ultrasonic image generated by the ultrasonic image generating unit 130.

2 is a flowchart of a photoacoustic imaging method according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the photoacoustic imaging method according to the present exemplary embodiment includes steps that are processed in time series in the photoacoustic imaging apparatus illustrated in FIG. 1. Therefore, although omitted below, the above descriptions of the photoacoustic imaging apparatus illustrated in FIG. 1 also apply to the photoacoustic imaging method according to the present embodiment.

In operation 200, the photoacoustic imaging apparatus applies light energy having a specific wavelength to an object including calcified tissue.

In operation 210, the photoacoustic imaging apparatus receives an optoacoustic signal generated by the object.

In operation 220, the optoacoustic imaging apparatus generates an optoacoustic image of calcified tissue from the received optoacoustic signal.

3 is a detailed flowchart of steps 210 and 220 of the photoacoustic imaging method according to an exemplary embodiment of the present invention shown in FIG. 2.

In operation 300, the photoacoustic imaging apparatus receives the first photoacoustic signal by applying energy of a microcalcification-active wavelength band to the object.

In this case, the microcalcification reaction wavelength band may be determined as the wavelength band when the magnitude of the photoacoustic signal generated in the calcification tissue is larger than the first threshold value.

In operation 310, the photoacoustic imaging apparatus receives the second photoacoustic signal by applying energy of a microcalcification-inactive wavelength band to the object.

In this case, the fine calcified unreacted wavelength band may be determined as the wavelength band when the magnitude of the photoacoustic signal generated in the calcified tissue is smaller than the second threshold value.

In operation 320, the photoacoustic imaging apparatus determines whether the first photoacoustic signal is greater than the second photoacoustic signal. If the first optoacoustic signal is greater than or equal to the second optoacoustic signal, the operation proceeds to step 330, and if the first optoacoustic signal is smaller than the second optoacoustic signal, the operation proceeds to step 340.

In operation 330, the photoacoustic imaging apparatus determines that the object is a calcified tissue, and enhances the first photoacoustic signal.

In operation 340, the photoacoustic imaging apparatus determines that the object is a surrounding tissue, and removes the second photoacoustic signal.

In operation 350, the photoacoustic imaging apparatus performs image post-processing to generate a final photoacoustic image by using the enhanced first photoacoustic signal and the removed second photoacoustic signal.

4 shows the results of ex vivo experiments on biological tissue specimens.

4 (a) shows an ultrasound image, FIG. 4 (b) shows an optoacoustic image, FIG. 4 (c) shows a fusion image of an optoacoustic image and an ultrasound image, and FIG. 4 (d) shows a mammography image.

In the ultrasound image shown in FIG. 4A, it is difficult to observe microcalcified tissue due to low contrast. On the other hand, the photoacoustic image shown in Figure 4 (b) is an image of the calcified tissue in response to the incident laser of the optimum wavelength. Unlike the ultrasound image of FIG. 4 (a), the calcified tissue is clearly seen in the photoacoustic image of FIG. 4 (b).

The photoacoustic image shown in FIG. 4 (b) can clearly distinguish the difference between the calcified tissue and the existing surrounding tissue, and can distinguish all the microcalcified tissues distinguished from the Mammography image shown in FIG. 4 (d). have.

The fusion image of FIG. 4 (c) is displayed by overlapping the ultrasound image and the photoacoustic image, which helps to locate the calcified tissue.

FIG. 5 shows the magnitude of the photoacoustic signal generated according to the wavelength of the laser, and the microcalcification reaction wavelength section and the unreacted wavelength section.

Referring to FIG. 5, it can be seen that the maximum amplitude of the optoacoustic signal generated in the microcalcified tissue in the in vitro experiment is generated in the range of 680 nm to 710 nm.

FIG. 5 is a result of recording the optimum wavelength at which the photoacoustic signal is generated to the maximum for 7 breast tissue specimens, and calculating the average and standard deviation. Each experiment collected data 16 times. The optoacoustic image is optimally configured when the wavelength of the applied light energy is 680 nm to 710 nm, and the signal size becomes small enough that the image cannot be visually seen in the image due to a small response in the 800-1000 nm band.

Therefore, the microcalcifications appear by comparing the reactions of the calcification-active wavelength band (680-710 nm) and the microcalcification-inactive wavelength band (800-1000 nm). The form can be determined and provided to the user.

In the present invention, the degree of photoacoustic signal generation between the microcalcification-active wavelength band and the microcalcification-inactive wavelength band of FIG. 5 for effectively imaging the microcalcification and increasing the contrast with the surrounding tissue. In contrast, background image removal and calcification tissue signal amplification are performed.

6 shows the relationship between the laser wavelength and the light absorption coefficient μ _a for each tissue.

A short pulse of light energy is applied to the molecule, and the photoacoustic signal is acquired by the thermal expansion of the tissue generated accordingly, and an image is obtained by receiving the photoacoustic signal. In this process, the tissue reacts according to the wavelength of the applied light energy. This is different, and functionally divided molecular imaging is possible using this. By using these characteristics to contrast the response to each wavelength of microcalcification, it is possible to distinguish between calcified and surrounding tissues inside the breast and thyroid tissue.

The absorption spectrum is a function of the laser wavelength and the response seen in each tissue is different for each wavelength of the laser. The relationship between the wavelength-specific light absorption coefficients in each tissue is shown in FIG. 6, and functional imaging is possible using the same. That is, functional imaging is possible because other molecules, such as hemoglobin bound to oxygen and oxygenated dissociated hemoglobin in the blood, exhibit different absorption spectral characteristics in response to the incident laser.

If a laser pulse having a peak absorption wavelength is emitted, molecules corresponding to the wavelength absorb the laser energy to the maximum and are converted into heat.

If the laser pulse width is shorter than the heat transfer time of the absorbed energy defined by thermal confinement, the absorbed energy will cause transient thermoelastic expansion. Thus, an optoacoustic signal detected in the form of ultrasonic waves can be generated and imaged.

As a result, the condition for the photoacoustic imaging device to image the microcalcified tissue is that the absorption spectral characteristics of the microcalcified tissue should be known.

From these conditions it is possible to determine the specific wavelength of the laser pulse and to produce the maximum optoacoustic signal in the microcalcified tissue larger than the surrounding tissue.

In the present invention, instead of measuring the absorption spectral characteristics of the microcalcified tissue, the optimal laser wavelength confirmed by an indirect method was confirmed through experiments.

By varying the wavelength between 680 nm and 1000 nm, photoacoustic signal magnitudes generated from in vitro experiments with breast cancer specimens containing calcified tissue from patients can be measured.

The intensity of the optoacoustic signal produced by the target molecule is proportional to the amount of energy absorbed by the target molecule.

The total absorbed energy can be expressed by Equation 1 below. Therefore, the magnitude of the photoacoustic signal generated depends on the light absorption coefficient of the tissue.

Where Γ is the Gruneisen parameter without dimension, μ _a is the light absorption coefficient, and F is the light fluence (J / m ² ) in the absorber.

After the object absorbs the laser energy, an optoacoustic signal is generated, propagated through the medium, and can be expressed by Equation 2 below.

Where p is the sound pressure, ν _s is the longitudinal velocity in the medium, t is the time, H is the heating function indicating the unit volume and the thermal energy stored per unit time.

In addition, Γ may be expressed as Equation 3 below.

Where β is the volumetric expansion coefficient of the medium and C _p is the heat capacity at a constant sound pressure.

In order to obtain the light absorption coefficient (μ _a ) using the above equation, F and Γ must be kept constant. If the incident energy density is fixed, F can be considered a constant, and Γ can be considered a constant by keeping the temperature of the medium constant even if the temperature increases after absorbing the energy of the emitted laser.

Therefore, when fixing these conditions, i.e., the ambient temperature and the amount of energy to be applied, F and Γ are fixed, and the amount of energy absorbed by the target is dependent on μ _a . Thus, the intensity of the optoacoustic signal is directly proportional to μ _a of the microcalcified tissue. μ _a determines the nature of the absorption spectrum and an indirect method is used to determine the optimal laser wavelength.

On the other hand, after converging the generated photoacoustic pressure through the ultrasonic transducer, the maximum photoacoustic signal value is recorded. In this case, it is preferable to use the mean and the standard deviation after focusing the beam several times.

Observing the response to the seven calcified tissues, and obtaining the average and standard deviation of the photoacoustic signal value, it can be seen that the calcified tissue shows the largest photoacoustic signal value between 680 nm and 710 nm.

This is effective for the imaging of actual human tissue, with the tendency of the photoacoustic signal values to maximize for wavelengths with low response in other skin and internal biological tissues.

Referring again to FIG. 6, a therapeutic window, a wavelength band with low response in other skin and internal biological tissues, is shown within a wavelength of 0.65 to 1.3 μm.

7 compares an optoacoustic image when a laser having a wavelength of 690 nm is applied to an object and an optoacoustic image when a laser having a wavelength of 800 nm is applied to an object.

The optoacoustic image when a laser having a wavelength of 690 nm is applied to an object shows signals from a fixing band for fixing the specimen and four microcalcified tissues.

On the other hand, the photoacoustic image when a laser having a wavelength of 800 nm is applied to an object is expressed as it is without changing the signal of the fixed band compared to when the wavelength is 690 nm, and the signal from the microcalcification is one out of four. Only signal is generated. In this case, it is not microcalcification, so it is removed from the image.

Signals simultaneously expressed in 690 nm and 800 nm images can be removed and only the remaining three microcalcification signals can be provided to the user.

The band compared to the 680 nm to 710 nm band may vary depending on the surrounding tissue of the calcified tissue. It is preferable to use a wavelength band as a comparison band that can minimize the photoacoustic signal reacting around the tissue where the calcified tissue is present.

For the breast or thyroid gland a comparison band can be determined between 800 nm and 1200 nm. In this case, it is preferable to determine a wavelength band in which the photoacoustic size of the comparison band is 50% or less than the photoacoustic size of the 680 nm to 710 nm band.

Embodiments of the present invention may be implemented in the form of program instructions that can be executed on various computer means and recorded on a computer readable medium. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the medium may be those specially designed and constructed for the present invention or may be available to those skilled in the art of computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tape, optical media such as CD-ROMs, DVDs, and magnetic disks, such as floppy disks. Magneto-optical media, and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

In the present invention as described above has been described by the specific embodiments, such as specific components and limited embodiments and drawings, but this is only provided to help a more general understanding of the present invention, the present invention is not limited to the above embodiments. For those skilled in the art, various modifications and variations are possible from these descriptions.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and all of the equivalents and equivalents of the claims, as well as the appended claims, will belong to the scope of the present invention. .

The photoacoustic imaging apparatus according to the present invention can be used as a real-time imaging apparatus used to diagnose and biopsy calcified tissue located in breast or thyroid tissue. Therefore, the present invention can be used in calcification imaging equipment for early diagnosis of cancer.

100: laser applying unit 100 105: photoacoustic signal receiving unit
110: calcification tissue determination unit 120: photoacoustic image post-processing unit
125: photoacoustic image generator 130: ultrasonic image generator
140: video output unit

Claims (18)

Applying light energy having a specific wavelength to a subject containing calcified tissue;
Receiving an optoacoustic signal generated by the object; And
Generating an optoacoustic image of the calcified tissue from the received optoacoustic signal. The method according to claim 1,
When the specific wavelength is in the 680 nm to 710 nm band, the photoacoustic image of the calcified tissue is generated by using the photoacoustic signal having a larger size than the surrounding biological tissue How to create an image. The method according to claim 1,
The photoacoustic image generating method of claim 2, wherein the light energy having two different wavelengths are applied to the object, and the calcified tissue is imaged using each photoacoustic signal generated by the object. The method of claim 3,
One wavelength is in the 680 nm to 710 nm wavelength band, and the other wavelength depends on the light absorption coefficient of the surrounding biological tissue. The method of claim 3,
Optoacoustic image generation method characterized in that for removing the surrounding images other than the calcified tissue by comparing the magnitude of each photoacoustic signal generated in the object. The method of claim 3,
Optoacoustic image generation method characterized in that for enhancing the calcified tissue image by comparing the magnitude of each photoacoustic signal generated in the object. The method of claim 3,
Applying light energy belonging to a wavelength band of 680 nm to 710 nm to the object, applying the magnitude of the photoacoustic signal generated in the object and light energy belonging to a wavelength band of 800 nm to 1000 nm to the object, Optoacoustic image generation method characterized in that to distinguish the calcified tissue in consideration of the ratio of the magnitude of the generated photoacoustic signal. The method according to claim 1,
Measuring a first optoacoustic signal for a fine calcification-active wavelength band;
Measuring a second optoacoustic signal for the microcalcification-inactive wavelength band; And
Reinforcing the first photoacoustic signal if the first photoacoustic signal is greater than the second photoacoustic signal, and removing the second photoacoustic signal if the first photoacoustic signal is smaller than the second photoacoustic signal. Optoacoustic image generation method comprising the step of performing. The method according to claim 1,
Measuring a first optoacoustic signal for a fine calcification-active wavelength band;
Measuring a second optoacoustic signal for the microcalcification-inactive wavelength band; And
Comparing the first image generated from the first photoacoustic signal and the second image generated from the second photoacoustic signal, an image of the calcified tissue is removed by using a signal appearing only in the first image by removing a signal that appears simultaneously. Optoacoustic image generation method comprising the step of generating. An optoacoustic signal receiver configured to receive an optoacoustic signal generated by the object; And
And an optoacoustic image generator for generating an optoacoustic image of the calcified tissue included in the object from the received photoacoustic signal. The method of claim 10,
The photoacoustic image generating device further comprises a laser applying unit for applying a light energy having a specific wavelength to the object containing calcified tissue. 12. The method of claim 11,
And the laser applying unit applies a laser having a wavelength in a range of 680 nm to 710 nm to the object. 12. The method of claim 11,
The laser applying unit applies light energy having two different wavelengths to the object,
The photoacoustic image generating unit may image the calcified tissue using each photoacoustic signal generated by the object. The method of claim 10,
The photoacoustic image generating unit
A calcified tissue determination unit that determines whether the calcified tissue is compared by comparing the magnitudes of the photoacoustic signals generated in the object; And
And a photoacoustic image post-processing unit for reinforcing the calcified tissue image according to the determination result of the calcified tissue determining unit and removing the surrounding image which is not the calcified tissue. The method of claim 10,
The photoacoustic image generating unit
And a calcified tissue determination unit configured to compare the magnitudes of the photoacoustic signals generated in the object to determine whether the calcified tissue is calcified.
The calcified tissue determination unit applies light energy belonging to a wavelength band of 680 nm to 710 nm to the object, and applies the magnitude of the photoacoustic signal generated from the object and light energy belonging to a wavelength band of 800 nm to 1000 nm to the object. And classify the calcified tissue in consideration of the ratio of the magnitude of the photoacoustic signal generated in the object. 15. The method of claim 14,
The photoacoustic signal receiver measures a first photoacoustic signal for a microcalcification-active wavelength band, a second photoacoustic signal for a microcalcification-inactive wavelength band,
If the first photoacoustic signal is greater than the second photoacoustic signal, the photoacoustic image post-processing unit reinforces the first photoacoustic signal, as a result of the determination of the calcification tissue determination unit.
And a photoacoustic image post-processing unit to remove the second photoacoustic signal when the first photoacoustic signal is smaller than the second photoacoustic signal. 15. The method of claim 14,
The photoacoustic signal receiver measures a first photoacoustic signal for a microcalcification-active wavelength band, a second photoacoustic signal for a microcalcification-inactive wavelength band,
The calcification tissue determination unit compares the first image generated from the first photoacoustic signal and the second image generated from the second photoacoustic signal,
The optoacoustic image post-processing unit removes a signal simultaneously appearing in the first image and the second image and uses a signal that appears only in the first image. A computer-readable recording medium storing a program for causing a computer to execute the method according to any one of claims 1 to 9.

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