JP2012070949A - Optoacoustic imaging device, method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To observe a deep part in an appropriate observation state without requiring a special operation concerning optoacoustic imaging.SOLUTION: An illumination means 13 irradiates the inner part of a subject with light from a light source 12. An ultrasonic probe 11 detects an optoacoustic signal generated inside the subject. An amplification means 15 amplifies the optoacoustic signal by gain corresponding to a position in a depth direction. A selection information acquisition means 17 acquires information, which affects an attenuation characteristic in the depth direction in the detected optoacoustic signal, as a gain selection information when the optoacoustic image is generated. A gain information storage means 19 stores the gain selection information and gain adjustment information by association. A gain control means 18 reads the gain adjustment information stored in association with the acquired gain selection information from the gain information storage means 19, and sets gain based on the read gain adjustment information in the amplification means 15.

Description

  The present invention relates to a photoacoustic imaging apparatus, method, and program, and relates to a photoacoustic imaging apparatus, method, and program that receive an acoustic signal generated by light irradiated in a subject and generate an image.

  An ultrasonic inspection method is known as a kind of image inspection method capable of non-invasively examining the state inside a living body. In the ultrasonic inspection, an ultrasonic probe capable of transmitting and receiving ultrasonic waves is used. When ultrasonic waves are transmitted from the ultrasonic probe to the subject, the ultrasonic waves travel inside the subject and are reflected at the tissue interface. By receiving the reflected sound wave with the ultrasonic probe and calculating the distance based on the time until the reflected ultrasonic wave returns to the ultrasonic probe, the internal state can be imaged.

  In addition, photoacoustic imaging is known in which the inside of a living body is imaged using a photoacoustic effect. In general, in photoacoustic imaging, a living body is irradiated with pulsed laser light such as a laser pulse. Inside the living body, the living tissue absorbs the energy of the pulsed laser light, and ultrasonic waves (photoacoustic signals) are generated by adiabatic expansion due to the energy. By detecting this photoacoustic signal with an ultrasonic probe or the like and constructing a photoacoustic image based on the detection signal, in-vivo visualization based on the photoacoustic signal is possible.

  Here, the ultrasonic diagnostic imaging apparatus has a function called STC (Sensitive Time Control) or TGC (Time Gain Control) for correcting attenuation of a signal from a deep part. Regarding STC processing, Patent Document 1 describes that a signal obtained from a probe is processed to form a reception beam signal corresponding to an ultrasonic beam, and the formed reception beam signal is subjected to STC processing. . Patent Document 1 describes that a plurality of STC data is stored in accordance with the type of probe and the application of the probe, and STC data is read from the STC data.

JP 2009-178277 A

  By the way, in the ultrasonic inspection method, the reflected sound wave with respect to the ultrasonic wave output from the ultrasonic probe is detected. In the photoacoustic imaging, the photoacoustic signal generated by the light emitted from the light irradiation unit is detected. The generation mechanism of ultrasonic waves (reflected sound waves and photoacoustic signals) detected by the ultrasonic probe is greatly different between the ultrasonic inspection method and the photoacoustic imaging. In the photoacoustic imaging, since the attenuation of the photoacoustic signal is added to the attenuation of the light, the signal level lowers deeply as compared with the ultrasonic inspection method. For this reason, in photoacoustic imaging, it is desirable to always apply STC at a certain level.

  Japanese Patent Application Laid-Open No. H10-228561 describes that in an ultrasonic image, STC data is selectively used according to the type and application of the probe. However, as described above, the generation mechanism of ultrasonic waves to be detected differs greatly between the ultrasonic inspection method and the photoacoustic imaging, and the technique described in Patent Document 1 cannot be directly applied to the photoacoustic imaging.

  In view of the above, an object of the present invention is to provide a photoacoustic imaging apparatus capable of observing a deep portion in an appropriate observation state without requiring a special operation in photoacoustic imaging.

  In order to achieve the above object, the present invention provides a light source, illumination means for irradiating the subject with light from the light source, and a photoacoustic signal generated in the subject by the light emitted from the illumination means. An ultrasonic probe for detecting the image, an image generation means for generating a photoacoustic image based on the photoacoustic signal, a photoacoustic signal input to the image generation means, or a pixel value in the photoacoustic image. Amplifying means for amplifying with a gain according to the position in the vertical direction and gain selection of information that affects the attenuation characteristics in the depth direction of the photoacoustic signal detected by the ultrasonic probe when generating the photoacoustic image The information stored in association with the gain selection information acquired by the selection information acquisition means from the selection information acquisition means acquired as information and the gain information storage means for storing the gain selection information and gain adjustment information in association with each other. Reads down adjustment information, provides a photoacoustic imaging apparatus characterized by a gain based on the read-out gain adjustment information and a gain control means for setting said amplifying means.

  In the photoacoustic imaging apparatus of the present invention, the illumination unit irradiates light in a switchable illumination range, and the gain selection information is an illumination range of light irradiated in the subject by the illumination unit. It is possible to adopt a configuration that includes light irradiation range information related to the.

  In the photoacoustic imaging apparatus of the present invention, the illumination unit includes a plurality of light irradiation units corresponding to divided areas obtained by dividing a portion of the subject to be imaged into a plurality of areas, and the light irradiation range. A configuration may be adopted in which the information includes information indicating which light irradiation unit of the plurality of light irradiation units is irradiated with light into the subject.

  The gain selection information may include measurement target tissue information related to a measurement target tissue instead of or in addition to the light irradiation range information. The measurement target tissue information may include one or both of designation information of the measurement target tissue and state information of the measurement target tissue.

  A configuration in which the amplifying unit amplifies the pixel value in the received photoacoustic signal or the photoacoustic image so as to compensate for the attenuation of the photoacoustic signal or the decrease in the pixel value according to the position in the depth direction. It can be.

  The gain information storage means may store the gain adjustment information as a LUT (Look Up Table) for each gain selection information. Instead of this, the gain information storage means may store a parameter of a predetermined function, which is a function in the depth direction, used when determining the gain as the gain adjustment information.

  The present invention also includes a step of detecting a photoacoustic signal generated in the subject by light irradiated in the subject, a step of generating a photoacoustic image based on the detected photoacoustic signal, When generating the photoacoustic image, the step of acquiring information that affects the attenuation characteristics in the depth direction of the detected photoacoustic signal as gain selection information, and the gain selection information and gain adjustment information are stored in association with each other. Reading out gain adjustment information stored in association with the acquired gain selection information from the gain information storage means, and a photoacoustic signal used in generating a photoacoustic image or a pixel value in the photoacoustic image A photoacoustic imaging method comprising a step of amplifying a signal with a gain according to a position in a depth direction based on the read gain adjustment information Subjected to.

  Furthermore, the present invention provides a computer for detecting a photoacoustic signal generated in the subject by light irradiated in the subject, and for generating a photoacoustic image based on the detected photoacoustic signal. And, in generating the photoacoustic image, associating the gain selection information with the procedure for obtaining information that affects the attenuation characteristics in the depth direction of the detected photoacoustic signal as gain selection information. A procedure for reading out gain adjustment information stored in association with the acquired gain selection information from the gain information storage means for storing the photoacoustic signal or the photoacoustic image used in generating the photoacoustic image And a procedure for amplifying the pixel value with a gain according to the position in the depth direction based on the read gain adjustment information.

  In the photoacoustic imaging apparatus, method, and program of the present invention, gain selection information and gain adjustment information are stored in the gain information storage means, and gain selection information is acquired and acquired when generating a photoacoustic image. The gain adjustment information stored in association with the gain selection information is read. By amplifying the photoacoustic signal or the pixel value in the photoacoustic image at the time of generating the photoacoustic image with a gain according to the position in the depth direction based on the read gain adjustment information, the user does not perform any special operation. Even in the photoacoustic image, the deep portion can be observed in an appropriate observation state.

  In particular, when the light irradiation range information is used as the gain selection information, even when the illumination range is narrow and the attenuation in the depth direction of the photoacoustic signal detected by the ultrasonic probe is large, for example, the position in the depth direction By amplifying the photoacoustic signal by the amplifying means so as to compensate for the attenuation of the photoacoustic signal corresponding to the depth, the deep portion can be observed in an appropriate observation state.

1 is a block diagram showing a photoacoustic imaging apparatus according to a first embodiment of the present invention. The perspective view which shows an illumination means and an ultrasonic probe. The graph which shows the attenuation characteristic of a photoacoustic signal. The graph which shows the relationship between an illumination range and μeff. The flowchart which shows an operation | movement procedure. The graph which shows the relationship between the illumination range for every measurement object structure | tissue, and μeff.

  Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 shows a photoacoustic imaging apparatus according to a first embodiment of the present invention. The photoacoustic imaging apparatus 10 includes an ultrasonic probe 11, a light source 12, an illumination unit 13, a signal processing unit 14, and a display unit 20. The light source 12 generates pulse laser light having a predetermined wavelength, for example. The illumination unit 13 irradiates the subject with the laser light from the light source 12. The range of light (illumination range) that the illumination unit 13 irradiates in the subject can be switched among a plurality of illumination ranges.

  The ultrasonic probe 11 detects an acoustic signal (hereinafter, also referred to as a photoacoustic signal) generated by irradiating a laser beam into the subject after the irradiation. Each of the ultrasonic probes 11 includes a plurality of ultrasonic transducers that detect photoacoustic signals and convert them into electrical signals. The plurality of ultrasonic transducers are arranged in a line along a predetermined direction, for example. The photoacoustic signal detected by the ultrasonic probe 11 is converted into a digital signal by an AD converter (not shown) or the like and then input to the signal processing means 14.

  The signal processing unit 14 includes an amplification unit 15, an image generation unit 16, a selection information acquisition unit 17, a gain control unit 18, and a gain information storage unit 19. The function of each part in the signal processing means 14 can be realized by a computer executing processing according to a predetermined program. Note that the gain information storage unit 17 may be referred to from the signal processing unit 14 and need not be provided in the signal processing unit 14.

  The amplification means 15 is means for performing STC processing. The amplifying unit 15 amplifies the photoacoustic signal detected by the ultrasonic probe 11 with a gain corresponding to the position in the depth direction. In other words, the amplifying unit 15 amplifies the photoacoustic signal with a gain corresponding to the elapsed time from the start of photoacoustic signal detection (start of sampling), that is, the position in the depth direction of the source of the photoacoustic signal. The amplifying unit 15 amplifies the photoacoustic signal so as to compensate the attenuation of the photoacoustic signal according to the position in the depth direction, for example.

  The image generation unit 16 generates a photoacoustic image based on the photoacoustic signal amplified by the amplification unit 15 according to the position in the depth direction. The display means 20 is a display device capable of displaying an image, such as a liquid crystal display device. The display unit 20 displays the photoacoustic image generated by the image generation unit 16 on the display screen.

  The selection information acquisition unit 17 acquires, as gain selection information, information that affects the attenuation characteristics in the depth direction of the photoacoustic signal detected by the ultrasound probe 11 when generating the photoacoustic image. In the present embodiment, the light irradiation range information related to the illumination range of the light irradiated by the illuminating means 13 into the subject is acquired as gain selection information. The illuminating unit 13 includes a plurality of light irradiation units corresponding to each of the divided areas obtained by dividing the part of the subject to be imaged into a plurality of areas. The selection information acquisition unit 17 acquires information indicating which light irradiation unit from among the plurality of light irradiation units has been irradiated with light as light irradiation range information.

  FIG. 2 shows the illumination means 13 and the ultrasonic probe 11. The illumination means 13 has six light irradiation parts 21a-21f, for example. The ultrasonic probe 11 has a plurality of ultrasonic transducers arranged in a line in the x direction. The light irradiation unit 21a and the light irradiation unit 21d are arranged at positions facing each other with the ultrasonic probe 11 sandwiched in the y direction. The light irradiation unit 21b and the light irradiation unit 21e are arranged at positions facing each other with the ultrasonic probe 11 sandwiched in the y direction. The light irradiation unit 21c and the light irradiation unit 21f are arranged at positions facing each other with the ultrasonic probe 11 sandwiched in the y direction. Light from the light source 12 (FIG. 1) is guided to the light irradiation units 21 a to 21 f using the optical fiber 22. It is assumed that the light powers irradiated to the subject by the light irradiation units 21a to 21f are the same.

  When generating the photoacoustic image, the six light irradiation units 21a to 21f included in the illumination unit 13 irradiate the subject with light in a desired pattern (combination). For example, in one aspect, the illuminating unit 13 irradiates the subject with light using a pair of the light irradiation unit 21a and the light irradiation unit 21d. In another aspect, in addition to the pair of the light irradiation unit 21a and the light irradiation unit 21d, the subject can be irradiated with light using the pair of the light irradiation unit 21b and the light irradiation unit 21e. In still another aspect, light may be irradiated into the subject using all of the light irradiation units 21a to 21f. The range (illumination range) of light irradiated in the subject changes according to the combination of the light irradiation units used when irradiating the subject with light.

  FIG. 3 shows the attenuation characteristics of the photoacoustic signal in the depth direction. Based on the simulation, the position and light in the depth direction of the sound source when the subject is irradiated with light of the same energy density in a total of five sizes from 8 cm (Φ8) to 0.3 cm (Φ0.3) in diameter. The relationship with the intensity of the acoustic signal was obtained. In the simulation, the light absorption coefficient μa was set to 0.1 and the light scattering coefficient μs was set to 10. The wavelength of the laser beam was 532 nm. In the graph of FIG. 3, the vertical axis represents the intensity of the photoacoustic signal, and the horizontal axis represents the position in the depth direction. The vertical axis shows a logarithmic scale.

  Referring to the graph shown in FIG. 3, it can be seen that the signal intensity of the photoacoustic signal becomes weaker as the position in the depth direction becomes deeper. That is, it can be seen that the attenuation of the photoacoustic signal increases as the position in the depth direction becomes deeper. Further, it can be seen that the intensity of the photoacoustic signal depends on the diameter of the irradiated light, and that the signal intensity of the optical signal increases as the diameter increases (the irradiation area of light increases). By compensating the attenuation characteristics shown in the graph of Fig. 3 for each light diameter and amplifying the photoacoustic signal so that the signal intensity is constant regardless of the position in the depth direction, deep observation is possible become.

  Returning to FIG. 1, the gain information storage unit 19 stores gain selection information and gain adjustment information in association with each other. For example, when the illumination unit 13 includes six light irradiation units 21a to 21f (FIG. 2), and the light is irradiated into the subject using any two, four, or six of them, the gain information storage unit 19 stores gain adjustment information corresponding to each of the three light irradiation ranges. Here, the gain adjustment information is information related to how the gain is adjusted when the amplifying unit 15 amplifies the photoacoustic signal with a gain corresponding to the position in the depth direction.

  For example, the gain adjustment information stored in association with the corresponding gain selection information when light is irradiated from the two light irradiation units 21 is irradiated with light from the two light irradiation units 21 using a simulation or the like. This can be determined by obtaining the attenuation characteristic of the photoacoustic signal in the depth direction. Similarly, gain adjustment information stored in association with gain selection information corresponding to when light is irradiated from the four light irradiation units 21 and when light is irradiated from the six light irradiation units 21 is also, for example, It can be determined by finding the attenuation characteristics of the photoacoustic signal in the depth direction using simulation etc.

  The gain information storage unit 19 can store gain adjustment information as a LUT (Look Up Table) for each gain selection information. For example, the gain information storage unit 19 stores an LUT for determining a gain for amplifying the photoacoustic signal at the position from the position in the depth direction corresponding to each of the three light irradiation range information. . Alternatively, the gain information storage unit 19 may store, as gain adjustment information, a parameter of a predetermined function that is a function in the depth direction and is used when determining the gain when the amplifying unit 15 amplifies the photoacoustic signal. Good. As a parameter of the function, a coefficient of the position in the depth direction in the exponent part when the signal intensity characteristic (FIG. 3) of the photoacoustic signal is approximated using an exponential function can be considered.

例えばΦ０．３の光が照射されたときの光音響信号の深さ方向の位置Ｚに対する信号強度Ｉ（Ｚ）は、
Ｉ（Ｚ）＝ｅ^{−２．７９×Ｚ}
で求めることができる。ゲイン情報記憶手段１９は、上記表１の各光照射範囲に対応するμｅｆｆをゲイン調整情報として記憶する。この場合、ゲインは、例えば１／Ｉ（Ｚ）とすることができる。 For example, the signal intensity characteristic of the photoacoustic signal in each light irradiation range shown in FIG.
I (Z) = e− ^{μeff × Z}
Approximate. When μeff is calculated for each light irradiation range by approximation up to a position of 2 cm in the depth direction using the attenuation characteristic shown in FIG. 3, the following Table 1 is obtained.

For example, the signal intensity I (Z) with respect to the position Z in the depth direction of the photoacoustic signal when the light of Φ0.3 is irradiated is
I (Z) = e- ^{2.79 × Z}
Can be obtained. The gain information storage means 19 stores μeff corresponding to each light irradiation range in Table 1 as gain adjustment information. In this case, the gain can be set to 1 / I (Z), for example.

In the above description, the light irradiation range and the parameter relating to gain adjustment are stored in association with each other. However, a calculation formula for obtaining a parameter for each light irradiation range may be stored in the gain information storage unit 19. FIG. 4 shows the relationship between the light irradiation range and μeff. As shown in FIG. 4, μeff in each light irradiation range shown in Table 1 is plotted on a graph, and the relationship between the light irradiation range and μeff is approximated by a curve passing through the plotted points. For example, in FIG. 4, the approximate curve is obtained as y = 1.266x− ^0.7956 . The gain information storage unit 19 may store this approximate curve (its parameters) as gain adjustment information.

  The gain control unit 18 reads the gain adjustment information stored in association with the gain selection information acquired by the selection information acquisition unit 17 from the gain information storage unit 19. The gain control unit 18 sets the gain based on the read gain adjustment information in the amplification unit 15. The amplifying unit 15 amplifies the photoacoustic signal with a gain according to the position in the depth direction based on the gain adjustment information set by the gain control unit 18.

  For example, when the gain adjustment information is represented by LUT, the gain control means 18 reads the LUT stored in association with the light irradiation range information acquired by the selection information acquisition means 17 from the gain information storage means 19 and reads the read LUT. Is set in the amplification means 15. The amplifying means 15 amplifies the photoacoustic signal with a gain corresponding to the position in the depth direction using the set LUT.

  When the gain adjustment information is represented by a parameter relating to gain adjustment, the gain control means 18 reads a parameter (μeff) stored in association with the light irradiation range information acquired by the selection information acquisition means 17 from the gain information storage means 19. . When a calculation formula for obtaining a parameter is stored in the gain information storage unit 19, the calculation formula is calculated using the light irradiation range information acquired by the selection information acquisition unit 17, and the parameter may be obtained. The amplifying unit 15 amplifies the photoacoustic signal with a gain corresponding to the position in the depth direction based on, for example, a parameter read from the gain information storage unit 19.

  For example, the amplifying unit 15 amplifies the photoacoustic signal so that the photoacoustic signal is constant regardless of the position in the depth direction. Alternatively, the amplifying unit 15 may amplify the photoacoustic signal so that the attenuation characteristic of the photoacoustic signal after amplification exhibits a predetermined attenuation regardless of the light irradiation range in which the subject is irradiated with light. For example, in any light irradiation range, the attenuation characteristic is equivalent to the attenuation characteristic of the photoacoustic signal of Φ8 in FIG. 3, that is, in any light irradiation range, the signal intensity of the photoacoustic signal in the case of Φ8 is equivalent. The photoacoustic signal may be amplified so that a high signal intensity can be obtained.

  FIG. 5 shows an operation procedure. The light source 12 receives a trigger from a control unit (not shown) and generates pulsed laser light. The illumination unit 13 irradiates the subject with pulsed laser light from some of the plurality of light irradiation units, for example (step S1). The ultrasonic probe 11 detects a photoacoustic signal generated in the subject by irradiation with pulsed laser light (step S2). The detected photoacoustic signal is input to the signal processing means 14 via an AD converter (not shown) or the like.

  The selection information acquisition means 17 acquires the light irradiation range information in the illumination means 13 (step S3). The gain control means 18 reads the gain adjustment information stored in association with the light irradiation range information acquired in step S3 from the gain information storage means 19 (step S4). The gain control unit 18 sets a gain adjustment value corresponding to the position in the depth direction in the amplification unit 15 based on the read gain adjustment information. For example, when the gain information storage unit 19 stores the LUT as gain adjustment information, the gain control unit 18 sets the LUT stored in association with the acquired light irradiation range information in the amplification unit 15.

  The amplification unit 15 amplifies the photoacoustic signal with the gain set by the gain control unit 18 (step S5). The image generation unit 16 generates a photoacoustic image based on the photoacoustic signal amplified by the amplification unit 15 with a gain corresponding to the position in the depth direction (step S6). The display means 20 displays the generated photoacoustic image on a display screen such as a display monitor (step S7).

  In the present embodiment, the light information range information (gain selection information) and gain adjustment information are stored in the gain information storage unit 19. The selection information acquisition unit 17 acquires, for example, light irradiation range information when generating a photoacoustic image, and the gain control unit 18 obtains gain adjustment information stored in association with the acquired light irradiation range information as gain information storage unit. 19 is read out. The amplifying unit 15 amplifies a photoacoustic signal used for photoacoustic image generation with a gain corresponding to the position in the depth direction based on the read gain adjustment value. In this embodiment, since the gain adjustment in the STC is performed according to the light irradiation range, the user can observe the deep portion in the photoacoustic image in an appropriate observation state without performing a special operation.

  Next, a second embodiment of the present invention will be described. The configuration of the photoacoustic imaging apparatus of the present embodiment is the same as that of the photoacoustic imaging apparatus of the first embodiment shown in FIG. In photoacoustic imaging, it is considered that light diffusion when light irradiated into a subject travels in the depth direction and light absorption in a living tissue change according to the tissue to be measured and its state. In addition, it is considered that the attenuation characteristic when the photoacoustic signal generated by the light absorber travels in the direction of the ultrasonic probe 11 changes depending on the biological tissue to be measured and its state. In this embodiment, in addition to the light irradiation range information used in the first embodiment, measurement target tissue information related to the measurement target tissue is used as gain selection information.

  The gain information storage unit 19 stores gain adjustment information in association with light irradiation range information and measurement target tissue information. As the measurement target tissue information, one or both of designation information of a measurement target region (tissue) and state information of the region can be used. For example, information such as skin, breast, and built-in information can be considered as the designation information of the tissue to be measured. The internal organs may be further subdivided into esophagus, stomach, large intestine and the like. As the state information of the part, for example, information indicating the presence or absence of melanosis can be considered. For example, when the ultrasonic probe 11 to be used differs depending on the region to be measured, the selection information acquisition unit 17 obtains the type information of the ultrasonic probe 11 to be used from the ultrasonic probe 11. The read type information may be used as the measurement target tissue information.

  FIG. 6 shows the relationship between the illumination range and μeff for each tissue to be measured. The method for obtaining μeff is the same as in the first embodiment. Simulation is performed by changing the light scattering coefficient and the light absorption coefficient according to the measurement target tissue, and μeff in a plurality of light irradiation ranges is obtained for each measurement target tissue. FIG. 6 shows approximate curves that approximate the relationship between the light irradiation range and μeff based on the obtained μeff for three cases of “esophagus”, “skin / stomach”, and “breast”. The gain information storage means 19 can store approximate curves obtained for “esophagus”, “skin / stomach”, and “breast”. In this case, for example, when the measurement target tissue information acquired by the selection information acquisition unit 17 indicates “stomach”, the approximate curve stored in association with “skin / stomach” is read, and the selection is performed using the approximate curve. The gain adjustment value may be determined by calculating μeff for the light irradiation range corresponding to the light irradiation range information acquired by the information acquisition means 17.

  In the present embodiment, measurement target tissue information is used for gain selection information. The gain information storage means 19 stores the measurement target tissue information and gain adjustment information in association with each other, and stores the gain adjustment information stored in association with the measurement target tissue information acquired at the time of photoacoustic image generation. By amplifying the photoacoustic signal with a gain corresponding to the position in the depth direction based on the read gain adjustment value, STC processing corresponding to the tissue to be measured can be realized. For this reason, the user can observe the deep part in the photoacoustic image in an appropriate observation state without performing a special operation for each tissue to be measured.

  In each of the above embodiments, the example in which the STC process is realized by amplifying the photoacoustic signal used by the amplifying unit 15 to generate the photoacoustic image has been described, but the present invention is not limited to this. For example, when the image generation unit 16 generates a photoacoustic image without the STC, and the amplification unit 15 displays the generated photoacoustic image on the display unit 20, the pixel value of the photoacoustic image is expressed in the depth direction. Amplification may be performed according to the position of Even in this case, for example, the pixel value of the dark portion displayed in the dark can be brightened by amplifying the pixel value with a gain corresponding to the position in the depth direction, and the deep portion is observed in an appropriate observation state in the photoacoustic image. Can do.

  Although 1st Embodiment demonstrated the example which calculates | requires one parameter (microeff) about one light irradiation range, it is not limited to this. For example, in the graph of the attenuation characteristic of the photoacoustic signal (FIG. 3), the position in the depth direction may be divided into a plurality of ranges, and μeff may be obtained for each divided range. Specifically, for each illumination range, μeff in the range from 0 cm to 2 cm in the depth direction and μeff in the range from 2 cm to 8 cm in the depth direction are obtained, and these are associated with the light irradiation range. May be stored in the gain information storage means 19. In the second embodiment, the measurement target tissue information is used in addition to the light irradiation range information. However, the measurement target tissue information may be used instead of the light irradiation range information.

  As mentioned above, although this invention was demonstrated based on the suitable embodiment, the photoacoustic imaging device of this invention, a method, and a program are not limited only to the said embodiment, From the structure of the said embodiment. Various modifications and changes are also included in the scope of the present invention.

10: Photoacoustic imaging apparatus 11: Ultrasound probe 12: Light source 13: Illumination means 14: Signal processing means 15: Amplification means 16: Image generation means 17: Selection information acquisition means 18: Gain control means 19: Gain information Storage means 20: Display means 21: Light irradiation unit 22: Optical fiber

Claims (10)

A light source;
Illumination means for irradiating the subject with light from the light source;
An ultrasonic probe for detecting a photoacoustic signal generated in the subject by light irradiated from the light irradiation means;
Image generating means for generating a photoacoustic image based on the photoacoustic signal;
Amplifying means for amplifying a photoacoustic signal input to the image generating means or a pixel value in the photoacoustic image with a gain according to a position in a depth direction;
Selection information acquisition means for acquiring, as gain selection information, information that affects the attenuation characteristics in the depth direction of the photoacoustic signal detected by the ultrasonic probe when generating a photoacoustic image;
The gain adjustment information stored in association with the gain selection information acquired by the selection information acquisition unit is read from the gain information storage unit that stores the gain selection information and gain adjustment information in association with each other, and the read gain adjustment A photoacoustic imaging apparatus comprising: gain control means for setting gain based on information in the amplification means.   The illumination means irradiates light in a switchable illumination range, and the gain selection information includes light irradiation range information related to an illumination range of light irradiated into the subject by the illumination means. The photoacoustic imaging apparatus according to claim 1.   The illuminating means includes a plurality of light irradiation units corresponding to each of the divided regions obtained by dividing a part to be imaged of the subject into a plurality of regions, and the light irradiation range information is included in the plurality of light irradiation units. The photoacoustic imaging apparatus according to claim 2, wherein the photoacoustic imaging apparatus includes information indicating from which light irradiation unit the light is irradiated into the subject.   The photoacoustic according to claim 2 or 3, wherein the gain selection information includes measurement target tissue information related to a measurement target tissue instead of or in addition to the light irradiation range information. Imaging device.   The photoacoustic imaging apparatus according to claim 4, wherein the measurement target tissue information includes one or both of designation information of a measurement target tissue and state information of the measurement target tissue.   The amplifying unit amplifies a pixel value in the received photoacoustic signal or the photoacoustic image so as to compensate for attenuation of the photoacoustic signal or a decrease in the pixel value according to the position in the depth direction. The photoacoustic imaging apparatus according to claim 1, wherein   The photoacoustic imaging according to any one of claims 1 to 6, wherein the gain information storage means stores the gain adjustment information as a LUT (Look Up Table) for each gain selection information. apparatus.   7. The gain information storage means stores a parameter of a predetermined function, which is a function in the depth direction, used when determining the gain as the gain adjustment information. The photoacoustic imaging apparatus in any one. Detecting a photoacoustic signal generated in the subject by light irradiated in the subject;
Generating a photoacoustic image based on the detected photoacoustic signal;
Obtaining the information that affects the attenuation characteristics in the depth direction of the detected photoacoustic signal when generating the photoacoustic image as gain selection information;
Reading gain adjustment information stored in association with the acquired gain selection information from gain information storage means for storing the gain selection information and gain adjustment information in association with each other;
Amplifying a photoacoustic signal used in generating a photoacoustic image or a pixel value in the photoacoustic image with a gain corresponding to a position in a depth direction based on the read gain adjustment information. The photoacoustic imaging method characterized by the above-mentioned. On the computer,
A procedure for detecting a photoacoustic signal generated in the subject by light irradiated in the subject;
Generating a photoacoustic image based on the detected photoacoustic signal;
When generating the photoacoustic image, a procedure for acquiring information that affects the attenuation characteristics in the depth direction of the detected photoacoustic signal as gain selection information;
A procedure for reading out gain adjustment information stored in association with the acquired gain selection information from gain information storage means for storing the gain selection information and gain adjustment information in association with each other;
Amplifying a photoacoustic signal used in generating the photoacoustic image or a pixel value in the photoacoustic image with a gain according to a position in the depth direction based on the read gain adjustment information; A program to be executed.

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