JP6501820B2 - Processing device, processing method, and program - Google Patents

Description

  The present invention relates to a signal processing apparatus and an object information acquiring method used for an object information acquiring apparatus which acquires object information by detecting a photoacoustic wave generated by irradiating light.

  In the medical field, in recent years, photoacoustic imaging (PAI: Photoacoustic Imaging) in which biological function information can be obtained using light and ultrasonic waves has been proposed as one of devices capable of non-invasive imaging of the inside of a living body, Development is in progress.

  In photoacoustic imaging, a photoacoustic effect is generated in which a pulse light generated from a light source is irradiated to a subject and absorption of light propagated and diffused in the subject generates a photoacoustic wave (typically, an ultrasonic wave). It is a technology that uses it to image the internal tissue that is the source of photoacoustic waves. Time-dependent changes in the received photoacoustic wave are detected at a plurality of points, and the obtained signal is mathematically analyzed, that is, reconstructed, and information related to the optical characteristic value inside the object is visualized in three dimensions Do.

  When near-infrared light is used for pulsed light, near-infrared light easily penetrates the water that makes up the majority of the living body, and it is likely to be absorbed by hemoglobin in the blood, so it is possible to image a blood vessel image it can. Furthermore, oxygen saturation in blood, which is functional information, can be measured by comparing blood vessel images of pulsed light of different wavelengths. Since blood around malignant tumors is considered to have lower oxygen saturation than blood around benign tumors, it is expected that it will be possible to distinguish between good and bad tumors by knowing oxygen saturation.

  Patent Document 1 discloses imaging the concentration distribution of a substance constituting a living body by photoacoustic imaging.

JP, 2010-35806, A

  However, as described in Patent Document 1, in photoacoustic imaging, when a photoacoustic wave is imaged, an artifact appearing at a position where the light absorber does not actually exist hinders observation of the light absorber.

  For example, when the subject is held by a holding plate whose acoustic impedance is different from that of the subject, photoacoustic waves generated in the subject are multiply reflected in the holding plate. Then, when the photoacoustic wave thus multiply reflected is detected and imaged, an artifact due to the multiple reflection appears. These artifacts make it difficult to distinguish the image of the light absorber actually present.

  Therefore, the present invention has an object to provide a signal processing apparatus used in an object information acquiring apparatus which makes it easy to distinguish an image of an optical absorber and an artifact and a signal processing method used in an object information acquiring method.

Processing apparatus according to the present invention, the image data to obtain image data indicating the distribution of the obtained, the subject of the optical characteristic value obtained on the basis of the photoacoustic wave detection signal generated by the light to the subject is irradiated Acquisition means, area information acquisition means for acquiring first area information indicating a first confidence area corresponding to an area sufficiently irradiated with light, inside the subject, image data, and first area information based on having the image data, the image data output means for displaying an image showing a first confidence region, and operating means capable of receiving an input from an operator on the display means.

  According to the present invention, it is possible to provide a signal processing apparatus used in an object information acquiring apparatus which makes it easy to distinguish an image of an optical absorber and an artifact, and a signal processing method used in an object information acquiring method.

Diagram for explaining the principle of the present invention A figure showing composition of a subject information acquisition device concerning a 1st embodiment The figure which shows the flowchart of the object information acquisition method based on 1st Embodiment. The figure which shows the example of 1st measurement conditions and 2nd measurement conditions based on 1st Embodiment. The figure which shows another example of 1st measurement conditions and 2nd measurement conditions based on 1st Embodiment. The figure which shows another example of 1st measurement conditions and 2nd measurement conditions based on 1st Embodiment. The figure which shows another example of 1st measurement conditions and 2nd measurement conditions based on 1st Embodiment. The figure which shows another example of 1st measurement conditions and 2nd measurement conditions based on 1st Embodiment. A diagram showing an example of a display device on which image data is displayed according to the first embodiment A diagram showing another example of a display device on which image data is displayed according to the first embodiment A figure showing a flow figure of a subject information acquisition method concerning a 2nd embodiment The figure which shows the example of the display apparatus which displayed image data and light quantity distribution based on 2nd Embodiment. The figure which shows another example of the display apparatus on which image data and light quantity distribution based on 2nd Embodiment were displayed. The figure which shows another example of the display apparatus on which image data and light quantity distribution based on 2nd Embodiment were displayed. The figure which shows the flowchart of the object information acquisition method based on 3rd Embodiment. A diagram showing an example of a display device on which image data and a trust region are displayed according to the third embodiment

  Because the artifacts are highly reproducible, they are observed the same way if they are measured in the same way. Therefore, it is difficult to distinguish the image of the light absorber from the artifact because the artifact appears in the same manner in the measurement.

  The present invention performs a plurality of measurements under different measurement conditions in photoacoustic imaging and displays the results so that they can be compared. This makes it possible to distinguish between the image of the light absorber and the artifact.

  First, the principle of the present invention will be described with reference to FIG. FIG. 1 shows an image of the positional relationship (measurement condition) between the irradiation light, the acoustic wave detector, and the object and an initial sound pressure distribution obtained in the positional relationship. Here, the subjects 130 and 131 have light absorbers 135 and 136 at the same position, respectively.

  Under the measurement conditions shown in FIG. 1A, the light 121 of the first measurement condition is irradiated on the surface of the object 130 acoustically connected to the detection surface of the acoustic wave detector 140.

  Further, under the measurement conditions shown in FIG. 1B, the light 122 of the second measurement condition is irradiated on the surface of the object 131 facing the acoustic wave detector 141. Further, in FIG. 1B, a part of the acoustic wave detector 141 is not acoustically connected to the subject 131.

  Furthermore, the initial sound pressure distribution obtained under the measurement conditions of FIG. 1 (a) is shown in FIG. 1 (c). The initial sound pressure distribution obtained under the measurement conditions of FIG. 1 (b) is shown in FIG. 1 (d).

  By comparing FIG. 1 (c) with FIG. 1 (d), it can be seen that the appearance positions of the artifacts 192 and 194 differ depending on the measurement conditions. On the other hand, it can be seen that the appearance positions of the light absorber images 191 and 193 are the same even if the measurement conditions are changed. This is because the generation process of the artifact differs depending on the measurement conditions. Hereinafter, the generation process of the artifact under each measurement condition will be described.

  Under the measurement condition of FIG. 1A, the light 121 under the first measurement condition partially turns around the surface of the acoustic wave detector 140 to generate a photoacoustic wave. Then, the photoacoustic wave generated on the surface of the acoustic wave detector 140 appears as an artifact 192 due to multiple reflection or the like in the acoustic matching layer of the acoustic wave detector 140 or the like.

  Further, under the measurement condition of FIG. 1B, the light of the second measurement condition in which the object 131 is moved to the portion of the acoustic wave detector 141 which is not acoustically connected to the object 131. 122 directly enters, and a photoacoustic wave is generated on the surface of the acoustic wave detector 141. Then, this photoacoustic wave appears as an artifact 194 due to multiple reflection at the acoustic matching layer of the acoustic wave detector 141 and the like.

  Thus, the image of the light absorber and the artifact can be determined by comparing FIG. 1 (c) and FIG. 1 (d), which are initial sound pressure distributions under different measurement conditions.

  As described above, by displaying image data obtained under a plurality of measurement conditions so as to be compared with each other, it is possible to provide an object information acquiring apparatus that can easily distinguish between an image of an optical absorber and an artifact.

  In the present invention, the image data refers to data for causing the display means to display information related to the optical characteristic value. Further, the optical characteristic value is related to the initial sound pressure and the light energy density obtained by reconstructing the detection signal, or the light absorption coefficient obtained by performing the light amount correction on them Including those that do.

  Hereinafter, embodiments of the present invention will be described.

First Embodiment
FIG. 2 is a block diagram showing the configuration of the object information acquiring apparatus according to the present embodiment, and a light source 210, an optical system 220, an optical system scanning mechanism 221, an object 230, an acoustic wave detector 240, an acoustic wave detector The scanning mechanism 241, the signal processing device 250, the memory 260, and the display device 280 are included. The signal processing apparatus 250 according to the present embodiment includes a measurement condition setting module 251 as a measurement condition setting unit, an image data acquisition module 252 as an image data acquisition unit, an image data output module 253 as an image data output unit, and light intensity distribution acquisition. A light amount distribution acquisition module 254 as a part and a trust area acquisition module 255 as a trust area acquisition part are provided.

  And FIG. 3 is a figure which shows the flow of the object information acquisition method using the object information acquisition apparatus which concerns on this embodiment shown in FIG.

  First, the measurement condition setting module 251 controls the light source 210, the optical system 220, and the acoustic wave detector 240 to set the first measurement condition, and the object 230 is irradiated with light of the first measurement condition (see FIG. S10). Then, the acoustic wave detector 240 detects the first photoacoustic wave generated in the subject 230 by the light of the first measurement condition, and obtains a first detection signal (S20).

  Next, the image data acquisition module 252 as a first image data acquisition unit performs reconstruction processing using this first detection signal to obtain a first initial sound pressure distribution as first image data. Are stored in the memory 260 (S30).

  Subsequently, the measurement condition setting module 251 sets the light source 210, the optical system 220, and the acoustic wave detector 240 to the second measurement condition, and the object 230 is irradiated with the light of the second measurement condition (S40) . Then, the acoustic wave detector 240 detects the second photoacoustic wave generated in the subject 230 by the light of the second measurement condition, and obtains a second detection signal (S50).

  Next, the image data acquisition module 252 as a second image data acquisition unit performs a reconstruction process using this second detection signal to obtain a second initial sound pressure distribution as second image data. Are stored in the memory 260 (S60).

  Next, the first image data and the second image data stored in the memory 260 can be compared so that the image data output module 253 can compare the first image data and the second image data on the display device 280. It outputs to the display apparatus 280 (S70).

  Then, the first image data and the second image data are displayed on the display device 280 so that the first image data and the second image data output to the display device 280 can be compared.

  Note that the image data acquisition module 252 can perform reconstruction using a known reconstruction method such as a universal back projection method in which the differentially processed signals are superimposed, and acquire an initial sound pressure distribution.

  Also, the program including the above steps may be executed by the signal processing device 250 as a computer.

(S10, S40: Process of setting measurement conditions)
Next, setting of measurement conditions shown in S10 and S40 of FIG. 3 will be described in detail.

  Hereinafter, an example in which the measurement condition setting module 251 sets measurement conditions will be described. The measurement condition in the present invention is a concept including the irradiation condition (irradiation position, irradiation angle, irradiation intensity) of the irradiation light and the detection position of the acoustic wave detector.

  First, an example of changing the irradiation condition of the irradiation light as the measurement condition will be described.

(1. Example of irradiating light to different positions on the surface of the subject)
First, an example of measurement conditions in which the light of the first measurement condition and the light of the second measurement condition are irradiated to different positions on the surface of the object will be described with reference to FIGS. 4 and 5.

  Under the first measurement condition shown in FIG. 4A, light 425 of the first measurement condition from the optical system 420 is applied to the surface of the object 430 acoustically connected to the detection surface 445 of the acoustic wave detector 440. Irradiate. Next, under the second measurement condition shown in FIG. 4B, from the optical system 421 on the surface opposite to the surface of the object 431 acoustically connected to the detection surface 446 of the acoustic wave detector 441 The light 426 of the second measurement condition is irradiated.

  As described above, when light is irradiated to different positions on the surface of the object under each measurement condition and each measurement result is used as image data, artifacts appear at different positions because the artifact generation process is different. Therefore, the image of the light absorber and the artifact can be discriminated by displaying the image data obtained by irradiating light to different positions on the surface of the subject so as to be comparable.

  The present invention can also be applied under the measurement conditions as shown in FIG. The first measurement condition shown in FIG. 5 (a) is the same as the measurement condition shown in FIG. 4 (a). On the other hand, the second measurement condition shown in FIG. 5 (b) is the light 525 under the same measurement condition as that shown in FIG. 4 (a) and the light under the same measurement condition as that shown in FIG. 4 (b). The surface of the object 531 is irradiated with 526.

  Thus, even when light of the second measurement condition includes light irradiated to a position on the surface of the subject different from the light of the first measurement condition in addition to the light of the first measurement condition, an artifact Because the position and the intensity at which they occur are different, it is possible to distinguish the image of the light absorber from the artifact.

  The irradiation position on the object surface may be changed by changing the beam profile of light on the object surface under each measurement condition.

  Further, as the position irradiated to the surface of the object largely varies depending on the measurement condition, the generation position of the artifact also largely varies, so it is preferable to largely vary the irradiation position depending on the measurement condition.

(2. Example of irradiating light at different angles between the surface of the object and the irradiation direction)
Next, an example of measurement conditions in which the irradiation angle, which is the angle between the surface of the object and the irradiation direction of light, is different will be described using FIG.

  The first measurement conditions shown in FIG. 6 (a) are the same as the measurement conditions shown in FIG. 4 (a). On the other hand, the second measurement condition shown in FIG. 6B is the light from the optical system 621 under the first measurement condition at the same position as the irradiation position of the light 625 under the first measurement condition shown in FIG. The light 626 of the second measurement condition is irradiated at an irradiation angle different from 625.

  Also in this case, when the image data obtained under the measurement conditions shown in FIG. 6A is compared with the image data obtained under the measurement conditions shown in FIG. 6A, the position where the artifact appears is different.

  Therefore, the light absorber and the artifact can be discriminated by displaying so that image data obtained under a plurality of measurement conditions where the angle between the surface of the object and the irradiation direction is different can be compared.

  In addition, since the generation | occurrence | production position of an artifact will also differ widely, so that the irradiation angle largely changes with measurement conditions, it is preferable to make an irradiation angle differ largely by measurement conditions.

(3. Example of irradiating light of different irradiation intensity)
Next, an example of measurement conditions in which the irradiation intensity of light of each measurement condition is different will be described with reference to FIG.

  Under the measurement conditions shown in FIG. 7, the optical system includes a plurality of light irradiation units, and a plurality of lights are irradiated from different light irradiation units to different positions on the surface of the object.

  Here, the light 725 of the first measurement condition shown in FIG. 7A and the light 727 of the second measurement condition shown in FIG. 7B are irradiated with light at the same position, and are shown in FIG. 7A. The light 726 of the first measurement condition and the light 728 of the second measurement condition shown in FIG. 7B are irradiated with light at the same position.

  Under the measurement conditions shown in FIG. 7A, the surface of the object 730 acoustically connected to the acoustic wave detector 740 is irradiated with the light 725 of weak intensity, and the light 725 is strong on the surface of the object 730 opposed thereto. The light 726 of intensity is emitted.

  On the other hand, under the measurement conditions shown in FIG. 7B, the surface of the object 731 acoustically connected to the acoustic wave detector 741 is irradiated with light 727 of high intensity, and the surface of the object 731 opposed thereto is irradiated. Is irradiated with light 728 of weak intensity.

  When light is irradiated from the plurality of light irradiation units, photoacoustic waves corresponding to the respective irradiation lights from the respective light irradiation units are generated. Then, artifacts corresponding to the intensities of the respective illumination light appear, and image data in which the artifacts are added is obtained. Therefore, since the ratio of the intensity of the image of the light absorber to the intensity of the artifact varies depending on the measurement conditions, the image of the light absorber can be distinguished from the artifact.

  As a method of changing the irradiation intensity of light of each measurement condition, a method of providing an optical system with a filter for attenuating light, a method of adjusting an output of a light source corresponding to light of each measurement condition, etc. can be considered. Any other method may be used as long as the irradiation intensity of light of each measurement condition can be changed.

  As described above, the method of changing the measurement conditions by changing the plurality of irradiation intensities can reduce the drive of the optical system compared to the method of changing the irradiation position and the irradiation angle. In particular, when adjusting the output of the light source, the drive of the optical system can be significantly reduced. Therefore, mechanical movement of the apparatus can be reduced, and automation of measurement can be easily realized.

  In addition, when irradiating light from several light irradiation parts, it is preferable to differ irradiation intensity in each measurement conditions in the state which fixed the optical system. By fixing the optical system, the accuracy of the irradiation position can be improved.

  In the present invention, when the irradiation intensity of the light of the first measurement condition and the irradiation intensity of the light of the second measurement condition are different, when there is one light emitting portion of the optical system, the light of each of the measurement conditions is It simply means that the radiation intensity of Further, in the case where there are a plurality of light emitting portions of the optical system, it means that the irradiation intensity of at least one of the plurality of lights from the plurality of light emitting portions is different.

  Next, an example of changing the detection position of the acoustic wave detector as the measurement condition will be described with reference to FIG.

(4. Example of detecting photoacoustic wave at different positions of detection surface of acoustic wave detector)
The first measurement conditions shown in FIG. 8 (a) are the same as the measurement conditions shown in FIG. 4 (a).

  On the other hand, under the second measurement condition shown in FIG. 8B, the irradiation condition of the light 826 of the second measurement condition is the same as the irradiation condition of the light 825 of the first measurement condition, but the acoustic wave detector The position of the detection surface 846 of 841 is different from the position of the detection surface 845 of the acoustic wave detector 840 under the first measurement condition.

  Then, as shown in FIG. 8, even when the position of the detection surface of the acoustic wave detector differs depending on each measurement condition, an artifact appears at a different position depending on each measurement condition.

  This is because the presence or absence of multiple reflections generated when light is irradiated to the surface of the acoustic wave detector, the propagation path of the photoacoustic wave, and the like depend on the position of the acoustic wave detector. Therefore, depending on the position of the acoustic wave detector, the appearance position of the artifact depends on the position of the detection surface of the acoustic wave detector. Therefore, the image of the light absorber and the artifact can be determined by comparing and displaying a plurality of image data obtained by changing the position of the detection surface of the acoustic wave detector according to the measurement conditions.

  Even when the angle formed by the detection surface of the acoustic wave detector and the object is changed under each measurement condition, the position where the artifact appears differs depending on each measurement condition. In this case, by changing the angle formed by the detection surface of the acoustic wave detector and the object surface, the position of the detection surface of the acoustic wave detector changes as a result under each measurement condition. That is, in the present invention, that the position of the detection surface of the acoustic wave detector is different includes that the angle formed by the detection surface of the acoustic wave detector and the surface of the object is different.

  In the processes of S10 and S40, when light is irradiated to a plurality of positions or when light is irradiated from a plurality of light irradiation units, those lights may not be simultaneously irradiated. That is, light may be sequentially irradiated to each irradiation position or light may be sequentially irradiated from each irradiation unit.

  When light is irradiated to a plurality of different positions, it is preferable to scan the optical system by the optical system scanning mechanism. At this time, the measurement condition setting module may control the optical system scanning mechanism to scan the optical system.

  In addition, when the detection surface of the acoustic wave detector detects photoacoustic waves at a plurality of positions, the photoacoustic waves may be detected at a plurality of positions using a plurality of acoustic wave detectors. The wave detector may be scanned by an acoustic detector scanning mechanism to detect photoacoustic waves at a plurality of positions. At this time, the measurement condition setting module may control the acoustic wave detector scanning mechanism to scan the acoustic wave detector.

  In addition, the optical system and the acoustic wave detector may be scanned while maintaining the relative positional relationship between the optical system and the acoustic wave detector.

  In the present embodiment, the measurement condition setting module controls the drive of the light source or the optical system to set the first measurement condition and the second measurement condition. It may be set so as to be the measurement condition of and the second measurement condition.

  Moreover, when comparing a plurality of measurement conditions, if the display of the image data having different measurement conditions is increased, the determination accuracy between the image of the light absorber and the artifact is enhanced, so it is preferable to increase the measurement conditions.

(S70: Step of comparing and displaying the first image data and the second image data)
Next, an example of a method of displaying the first image data and the second image data shown in S70 of FIG. 3 so as to be compared with each other will be described.

  Hereinafter, an example in which parallel display, superimposed display, and alternate display are performed on the display device will be described.

(1. Example of displaying first image data and second image data in parallel)
First, a method of arranging and displaying the first image data and the second image data will be described with reference to FIG.

  A display device 980 shown in FIG. 9 includes a first display area 981 and a second display area 982. Then, the image data output module 253 outputs the first image data 991 to the first display area 981 and outputs the second image data to the second display area 982. As a result, the first image data 991 is displayed in the first display area 981, and the second image data is displayed in the second display area 982.

  In addition, the display device 980 includes a first operation unit 983 corresponding to the first display area 981 and a second operation unit 984 corresponding to the second display area 982. However, one operation unit may correspond to a plurality of display areas.

  Further, in the display device 980, the first pointer 985 in the first display area 981 is moved using the first operation unit 983, and the coordinates of the position designated by the first pointer 985 and the data of the coordinates are Information 987 such as values can be displayed.

  In addition, in order to make it easy to compare the image data displayed in the first display area 981 and the second display area 982, for example, when a certain coordinate in the first display area 981 is designated by the first pointer 985 , And a second pointer 986 is displayed at a position corresponding to the first pointer 985 in the second display area 982.

  Further, although it is preferable that the first display area 981 and the second display area 982 be displayed in the same place, range, and dynamic range in conjunction with each other, they may be adjusted individually.

  In addition, although it is preferable that the display area and the operation unit be provided in one display device, a plurality of display devices provided with the display area and the operation unit may be prepared.

  Thus, by displaying image data of different measurement conditions side by side, each image data can be diagnosed independently, so that the visibility of each image data is good. Therefore, the image of the light absorber and the artifact can be discriminated.

(2. Example of displaying first image data and second image data in a superimposed manner)
Next, an example of a method of superimposing and displaying the first image data and the second image data will be described with reference to FIG.

  The display device 1080 illustrated in FIG. 10 includes one display area 1081. Then, the image data output module 253 outputs the first image data 1091 and the second image data 1092 to one display area 1081. As a result, the first image data 1091 and the second image data 1092 are displayed superimposed on the display area 1081.

  In addition, the display device 1080 includes a first operation unit 1083 corresponding to the first image data 1091 and a second operation unit 1084 corresponding to the second image data 1092. Here, in order to correspond to two image data, two operation units are provided, but one operation unit may correspond to a plurality of image data.

  As shown in FIG. 10, when the image data is superimposed and displayed, the degree of transparency of each image data is changed and displayed so that each image data can be viewed even when a plurality of image data overlap. May be

  In addition, a color may be assigned to each piece of image data, and the intensity of the image data may be displayed by the shade of the color. Alternatively, shading may be assigned to each piece of image data, and the intensity of the image data may be represented by a color.

  In addition, it is preferable that the operation unit provided in the display device be used so that the operator can interactively set the transparency, the color, the gradation, and the like.

  Further, among the plurality of image data, only arbitrary image data may be superimposed and displayed. At this time, it is preferable that any image data can be selected by the operation unit.

  As described above, by superimposing and displaying a plurality of image data, it becomes easy to compare the coordinates, shape, size, etc. of the images, and it is easy to determine whether it is an image of an optical absorber or an artifact. Become.

(Example of alternately displaying the first image data and the second image data)
Next, an example of a method of alternately displaying the first image data and the second image data on the same coordinates in time will be described.

  The image data output module outputs each of the plurality of image data stored in the memory to one display area of the display device at different timings. Then, in one display area, a plurality of image data are switched and displayed at different timings.

  At this time, it is preferable that the image data output module output the respective image data at an arbitrary timing of the operator by the operation of the operation unit, but the output timing is determined in advance, and is automatically performed. You may output it. In the case of automatic output, when the last image data is output, the first output image data may be output.

  As described above, by alternately displaying each piece of image data in one display area, it is reduced that the respective pieces of image data are overlapped and hard to be seen, and it becomes easy to distinguish the image of the light absorber from the artifact.

  Note that, prior to the step of comparing and displaying the image data shown in S70, the signal processing device may perform preprocessing such as blurring processing and enhancement processing on the image data.

  Here, the blurring process is a process of blurring the image data, which removes high frequency random noise and lowers the sensitivity to the positional deviation between the measurement conditions. As the blurring process, specifically, a Gaussian filter, a spatial frequency low pass filter, a moving average filter or the like can be used.

  Further, the emphasizing process is a process of emphasizing a portion of the image data that matches the pattern unique to the light absorber. Specifically, a pattern unique to the light absorber may be used as a template, and a template matching method may be used for image data. Alternatively, a template matching method may be used with an artifact or a pattern unique to random noise as a template. At this time, processing is performed to increase or decrease the intensity of the image data of the region extracted by the template matching method, or to increase or decrease the intensity of image data of the region other than the region extracted by the template matching method. May be

  Thus, the image data of each measurement condition subjected to the pre-processing is image of light absorber or image data in which an artifact is emphasized. Therefore, by pre-processing the image data, when comparing the image data of the respective measurement conditions, it is possible to more easily distinguish between the light absorber and the artifact.

  As described above, the image of the light absorber and the artifact can be easily distinguished by comparing the image data obtained under different measurement conditions.

Second Embodiment
The present embodiment is different from the other embodiments in that the light intensity distribution in the subject under each measurement condition is displayed in addition to the image data obtained under each measurement condition. Here, the light amount distribution includes data to be displayed on a display device obtained by performing luminance value conversion or the like on the light amount distribution.

By the way, the initial sound pressure P ₀ of the photoacoustic wave depends on the light amount Φ as represented by the relation of equation (1).
P ₀ = Γ · φ · μ _a Formula (1)
Here, Γ is the Gruneisen constant, and μa is the light absorption coefficient. As represented by the equation (1), if the amount of light irradiated to the light absorber is a large value, the initial sound pressure of the generated photoacoustic wave also increases. That is, the SN ratio of the detection signal corresponding to the area irradiated with a large amount of light increases. Therefore, the image data of the area irradiated with a large amount of light is image data obtained from the detection signal having a large SN ratio, and therefore the reliability is high. On the contrary, the reliability of the image data in the area where the light quantity is not sufficiently irradiated is low. Therefore, in the present embodiment, by displaying the light quantity distribution in the subject of each measurement condition in addition to the image data obtained under each measurement condition, the image data of each measurement condition is highly reliable. The area can be determined.

  Below, the method to display light quantity distribution is demonstrated using the flowchart shown in FIG. The same processes as those in the flowchart shown in FIG. 3 are assigned the same process numbers and descriptions thereof will be omitted. Further, description will be made using the object information acquisition apparatus shown in FIG.

(S21, S51: step of acquiring light amount distribution)
First, the light quantity distribution acquisition module 254 of the signal processing device 250 acquires a first light quantity distribution based on the light of the first measurement condition, and acquires a second light quantity distribution based on the light of the second measurement condition Do.

  Here, the method of acquiring the light amount distribution may use a method of acquiring the light amount distribution in the object by calculating the light propagation in the object from the beam profile of the irradiation light to the object. Alternatively, the beam profile of the irradiation light to the object and the beam profile of the outgoing light exiting from the object may be measured, and the light quantity distribution in the object may be acquired from the relationship between the two. The beam profile of the irradiation light to the object may be the same if the irradiation setting does not change, so beam profile data stored in advance in the memory may be used.

(S71: Step of displaying image data and light quantity distribution)
Next, the image data output module 253 outputs the first light intensity distribution and the second light intensity distribution to the display 280, and causes the display 280 to display the first light intensity distribution and the second light intensity distribution. Hereinafter, display examples of the light amount distribution will be described with reference to FIGS.

  First, as shown in FIG. 12, an example will be described in which the image data of each measurement condition and the light quantity distribution are output to different display areas, and the respective display areas are displayed side by side.

  First, the image data output module 253 outputs the first image data 1291 to the first display area 1281, and outputs the second image data 1292 to the second display area 1282, and then to the third display area 1283. The first light amount distribution 1293 is output, and the second light amount distribution 1294 is output to the fourth display area 1284. Then, as shown in FIG. 12, on the display device 1280, each image data and each light amount distribution are displayed side by side.

  Thus, the visibility of each light quantity distribution can be made high by displaying each light quantity distribution in a separate display area.

  Next, as shown in FIG. 13, an example will be described in which the light quantity distribution of each measurement condition is superimposed on the image data corresponding to each light quantity distribution and displayed.

  First, the image data output module 253 outputs the first image data 1391 and the first light quantity distribution 1393 to the first display area 1381, and the second image data 1392 and the second light quantity distribution 1394 Output to the second display area 1382. Then, as shown in FIG. 13, the first image data 1391 and the first light quantity distribution 1393 are superimposed and displayed in the display area 1381, and the second image data 1392 and the second light quantity distribution are displayed in the display area 1382. The display is superimposed on 1394.

  Next, as shown in FIG. 14, an example will be described in which each image data and each light amount distribution are superimposed on one display area and displayed.

  First, the image data output module 253 outputs the first image data 1491, the second image data 1492, the first light amount distribution 1493, and the second light amount distribution 1494 to one display area 1481. Then, the first image data 1491, the second image data 1492, the first light amount distribution 1493, and the second light amount distribution 1494 are superimposed and displayed in the display area 1481.

  As for the display of the light quantity distribution, it is preferable to be able to set the transmittance, the color, the gradation, etc. as in the display of the image data according to the first embodiment. At this time, it is further preferable that the operation unit be configured so that the operator can operate interactively.

  In addition, the image data output module 253 may output the sensitivity distribution of the acoustic wave detector 240 to the display device 280 and cause the display device 280 to display the same as the light amount distribution described in the present embodiment. In the region where the sensitivity of the acoustic wave detector 240 is high, the SN ratio of the detection signal is high. Therefore, by displaying the sensitivity distribution of the acoustic wave detector 240 on the display device in addition to the image data, SN of the image data A highly reliable region obtained from the detection signal with a high ratio can be determined. In the present invention, the sensitivity of the acoustic wave detector includes the attenuation of the acoustic wave in the propagation path from the sound source to the acoustic wave detector, and the directivity angle of the acoustic wave detector.

Third Embodiment
The present embodiment is different from the other embodiments in that in the light amount distribution, a reliable region which is a region irradiated with sufficient light is acquired. Here, the term "reliable area" includes data to be displayed on display means obtained by performing luminance value conversion or the like on the reliable area.

  In photoacoustic imaging, it is preferable to emphasize and display the area | region to which light is fully irradiated among the light quantity distributions acquired in 2nd Embodiment. So, in this embodiment, the discriminability of the image of an optical absorber and an artifact is improved more using the reliability area | region which is an area | region to which light is fully irradiated among light quantity distributions.

  Hereinafter, a method of acquiring subject information using a confidence region will be described using a flow chart shown in FIG. The same processes as those in the flowchart shown in FIG. 3 are assigned the same process numbers and descriptions thereof will be omitted. Further, description will be made using the object information acquisition apparatus shown in FIG.

(S22, S52: step of acquiring a trust region)
First, the reliability area acquisition module 255 of the signal processing device 250 sets a threshold that is considered to be sufficient for each light quantity distribution.

  Next, the confidence region acquisition module 255 performs processing for increasing the light amount value in the region where the light amount value is larger than the threshold value or processing for decreasing the light amount value in the region where the value is smaller than the threshold value, and light is sufficiently irradiated. Acquire a trust region with the highlighted region. That is, the trust area acquisition module 255 acquires the first trust area based on the first light quantity distribution, and acquires the second trust area based on the second light quantity distribution. Here, it is preferable to set a desired level on the basis of the S / N ratio and the threshold at which a sufficient signal can be obtained.

  The trust area acquisition module 255 may acquire the trust area by binarizing the light quantity distribution based on the threshold.

  In addition, the trust area acquisition module 255 may take the logical product of the trust areas in each measurement condition and use it as the trust area.

(S72: Step of displaying image data and a confidence region)
Next, the image data output module 253 outputs the confidence region acquired in S22 or S55 to the display device 280, and causes the display device 280 to display the confidence region. In this process, the image data and the light amount distribution described above can be superimposed and displayed, or the image data and the light amount distribution can be displayed side by side.

  In this embodiment, as an example, an example shown in FIG. 16 in which a confidence region is superimposed and displayed on image data shown in FIG. 9 will be described.

  First, the image data output module 253 outputs the first image data 1691 and the first confidence region 1695 to the first display region 1681, and the second image data 1692 and the second confidence region 1696 as the second. Output to the display area 1682 of Then, the first image data 1691 and the first confidence region 1695 are superimposed and displayed in the first display region 1681, and the second image data 1692 and the second confidence region are displayed in the second display region 1682. 1696 is displayed superimposed.

  In the case where the image data and the confidence region are superimposed and displayed, it is preferable to change the degree of transparency of the image data or the confidence region. Preferably, the image data and the trust area are displayed in different colors. Furthermore, it is preferable to change the color for each measurement condition.

  In addition, when the light amount distribution is binarized and the confidence region is acquired, the outer periphery of the confidence region may be surrounded by a line. However, even when the confidence region is not obtained by binarization, predetermined values of the confidence region may be connected by a line to form the outer periphery of the confidence region.

  As described above, by displaying the reliable region to which light is sufficiently applied in addition to the image data, it is possible to easily compare the image data of the highly reliable region of the image data of each measurement condition. .

  Further, the trust area acquisition module 255 may acquire the trust area based on the sensitivity distribution of the acoustic wave detector 240, as in the case of the trust area based on the light quantity distribution described in the present embodiment. In this case, the image data output module 253 outputs the confidence region based on the sensitivity distribution of the acoustic wave detector 240 to the display device 280 and causes the display device 280 to display it.

  The confidence region based on the sensitivity distribution of the acoustic wave detector 240 is image data in which the region where the sensitivity of the acoustic wave detector 240 is high is emphasized. Therefore, the confidence region based on the sensitivity of the acoustic wave detector 240 also indicates a region obtained from the detection signal having a high SN ratio, like the confidence region based on the light quantity distribution.

  Therefore, by displaying a confidence region based on the sensitivity distribution of acoustic wave detector 240 on display 280 in addition to the image data, the reliability obtained from the detection signal having a high SN ratio among the plurality of image data High areas can be easily compared.

Fourth Embodiment
The present embodiment is different from the other embodiments in that image data is obtained based on the detection signal obtained by the acoustic wave detector and the confidence region obtained in the third embodiment.

  In the present embodiment, the image data acquisition module 252 acquires the image data in which the highly reliable area is emphasized by weighting the trust area to the optical characteristic value distribution obtained based on the detection signal.

  The confidence region may be weighted on the detection signal under each measurement condition. In this case, the confidence region is weighted to the signal strength of the detection time corresponding to the confidence region. Then, based on the detection signal weighted by the confidence region, it is possible to obtain image data in which a region with high reliability is emphasized.

  However, when the confidence region is binarized, only the signal strength of the detection time corresponding to the confidence region having a low value may be reduced. Also, even when the confidence region is not binarized, the signal strength of the detection time corresponding to the confidence region less than or equal to a predetermined value may be reduced.

  Here, as a method of weighting, for example, a method of multiplying an optical characteristic value distribution or a similarity distribution with a confidence region can be used. Note that processing other than multiplication may be performed as long as it is a method that can acquire a similarity distribution in which a highly reliable region is emphasized.

  Hereinafter, a method for acquiring object information according to the present embodiment will be described using the object information acquiring apparatus shown in FIG.

  For example, the image data acquisition module 252 acquires the initial sound pressure distribution by performing reconstruction processing on the first detection signal. Then, first image data is acquired by multiplying the initial sound pressure distribution by the first confidence region based on the first light amount distribution.

  Similarly, the image data acquisition module 252 acquires second image data by multiplying the second detection signal by the second confidence region based on the second light amount distribution.

  Then, the image data output module 253 displays the first image data and the second image data so that they can be compared by the display method described in the first embodiment.

  Since the image data displayed in this manner emphasizes the optical characteristic value of the region where the light quantity is sufficiently irradiated or the region where the sensitivity of the acoustic wave detector is high, the optical characteristic value with high reliability is high. Can be easily determined. Therefore, highly reliable optical characteristic values can be compared with each other to easily distinguish the image of the light absorber from the artifact.

Fifth Embodiment
Since many functional information obtained by photoacoustic imaging is information related to the light absorption coefficient, it is preferable that image data obtain information related to the light absorption coefficient.

  Therefore, in the present embodiment, information related to the light absorption coefficient distribution obtained by performing the light amount correction on the initial sound pressure distribution and the light energy density distribution is handled as the image data. That is, in the present embodiment, the image data is, for example, a light absorption coefficient distribution or an oxygen saturation distribution.

  Hereinafter, an example of the method for acquiring subject information according to the present embodiment will be described using a flowchart shown in FIG. The configuration will be described using the configuration of the object information acquisition apparatus shown in FIG.

  For example, in S30 according to the present embodiment, first, the image data acquisition module 252 uses the first detection signal acquired in S20 and the second light intensity distribution acquired in S21 based on Equation (1). , The first light absorption coefficient distribution as the first image data is acquired. Similarly, in S60 according to the present embodiment, the second image data is acquired using the second detection signal acquired in S50 by the image data acquisition module 252 and the second light quantity distribution acquired in S51. Obtain a second light absorption coefficient distribution as

  Then, the image data output module 253 outputs the first light absorption coefficient distribution and the second light absorption coefficient distribution to the display 280 so that the first light absorption coefficient distribution and the second light absorption coefficient distribution can be compared. The coefficients are displayed on the display 280.

  Thus, in the light absorption coefficient distribution in which the light quantity correction is performed on the initial sound pressure distribution, not only are the positions of the images of the light absorber under the respective measurement conditions identical, but also the intensities of the images of the light absorber It becomes the same under the measurement conditions of.

  On the other hand, the artifact can not be removed even if the light amount correction is performed, so the artifact appears at different positions depending on each measurement condition.

  Therefore, as in the present embodiment, by displaying image data based on information subjected to light amount correction under each measurement condition so as to be comparable, an image existing at the same position and with the same intensity as the image of the light absorber It can be determined. Therefore, discrimination between the image of the light absorber and the artifact can be easily performed.

  In the case where optical property values obtained by multiple measurements are used as image data, such as oxygen saturation, multiple times for acquiring a first oxygen saturation distribution as first image data Measurement of the first measurement condition. Then, different measurements may be taken as measurement of the second measurement condition, and a second oxygen saturation distribution as second image data may be acquired. Here, the different plural measurements refer to measurements in which the measurement conditions of at least one of the plural measurements are changed.

  The basic configuration of the subject information acquiring apparatus shown in FIG. 2 will be described below.

(Light source 210)
The light source 210 is a device that generates pulsed light. Although a laser is preferable as the light source 210 in order to obtain a large output, a light emitting diode or the like may be used. In order to effectively generate the photoacoustic wave, light must be irradiated for a sufficiently short time according to the thermal characteristics of the subject 230. When the subject 230 is a living body, the pulse width of pulse light generated from the light source 210 is preferably several tens nanoseconds or less. Moreover, the wavelength of pulsed light is a near-infrared area | region called the window of a biological body, and about 700 nm-1200 nm are preferable. The light in this region can reach relatively deep parts of the living body, and deep information can be obtained. Furthermore, it is preferable that the wavelength of the pulsed light has a light absorption coefficient higher than that of the observation target.

(Optical system 220)
The optical system 220 is a device for guiding the pulsed light generated by the light source 210 to the subject 230. Specifically, the optical system 220 is an optical device such as an optical fiber, a lens, a mirror, or a diffusion plate.

  In the present invention, the measurement conditions such as the irradiation shape of the pulsed light, the light density, and the irradiation direction to the object may be changed by using these optical devices at the required plural times of measurement. Also, these may be adjusted by the light source 210.

  Further, in order to acquire data in a wide range, the optical system scanning mechanism 221 configured to scan the optical system 220 may scan the optical system 220 to scan the irradiation position of the pulsed light. At this time, scanning may be performed in conjunction with the acoustic wave detector 240.

  Further, the optical system 220 is not limited to those listed above, and may be any type as long as it satisfies such a function.

(Subject 230)
The subject 230 is to be measured. As the subject 230, a living body or a phantom simulating a living body can be used.

  For example, when the subject 230 is a living body, the subject information acquiring apparatus according to the present invention can image a blood vessel or the like as a light absorber present inside the subject 230. Moreover, as a light absorber, hemoglobin, water, melanin, collagen, a lipid etc. with a comparatively large light absorption coefficient in a living body, and a biological tissue comprised from these are mentioned.

  Further, in the case of a phantom, a substance simulating the optical characteristics of the light absorber listed above may be enclosed inside the phantom.

(Acoustic wave detector 240)
The acoustic wave detector 240 detects the photoacoustic wave and converts it into an electrical signal.

  An acoustic wave detector scanning mechanism 241 configured to scan the acoustic wave detector 240 scans a single acoustic wave detector to move to a plurality of positions in order to detect a photoacoustic wave at a plurality of positions. Alternatively, multiple acoustic wave detectors may be installed at different places.

  Further, in the photoacoustic imaging, since the photoacoustic wave generated from the inside of the subject 230 is received by the acoustic wave detector 240, the acoustic wave detector 240 is made to prevent reflection and attenuation of the generated photoacoustic wave. Are required to be acoustically coupled to the subject 230. For example, an acoustic matching material such as acoustic matching GEL, water, or oil may be provided between the acoustic wave detector 240 and the subject 230.

  The acoustic wave detector 240 preferably has high sensitivity and a wide frequency band, and specifically, an acoustic wave detector using a PZT, PVDF, cMUT, Fabry-Perot interferometer, etc. may be mentioned. However, the present invention is not limited to the ones listed here, but may be anything as long as the function is satisfied.

(Signal processing device 250)
The signal processing device 250 performs amplification of the electrical signal obtained by the acoustic wave detector 240, conversion to a digital signal, and the like. Then, the converted digital signal is processed to obtain image data, and the image data is output to the display device 280. The signal processing apparatus 250 includes an AD converter (ADC), a measurement condition setting module 251, an image data acquisition module 252, an image data output module 253, a light quantity distribution acquisition module 254, a confidence region acquisition module 255, and the like.

  The modules included in the signal processing device 250 according to the present embodiment may be provided as independent configurations.

  When the module is configured as hardware, it can be configured as an FPGA, an ASIC, or the like. Also, each module may be configured as a program that causes a computer to execute each process.

  Specifically as a signal processing device, a computer, an electric circuit, etc. are mentioned. In order to obtain data efficiently, it is preferable to provide AD converters (ADCs) as many as the number of receiving elements of the acoustic wave detector 240, but one ADC may be used in sequence .

(Memory 260)
The memory 260 holds image data processed by the signal processing device 250. The memory holds image data obtained under different measurement conditions. It is preferable that the memory be prepared for the number of measurement conditions.

  Although the memory temporarily holds the image data so that a flexible display method can be performed, the signal processing device 250 sends the image data directly to the display device 280 without using the memory. It is also good.

  The signal processing device 250 may include the memory 260, and the display device 280 may include the memory 260.

(Display 280)
The display device 280 includes a display area for displaying image data. The display device 280 may also include a plurality of display areas. In the present invention, the display means refers to one display device or a plurality of display devices.

  In addition, the display device 280 preferably includes an operation unit used to operate display conditions and a pointer. Furthermore, it is preferable that one operation unit be provided in each display area. Further, the operation unit may be a touch panel or may be a hard operation such as a mechanical switch. The operation unit may be provided in a device other than the display device 280, for example, the signal processing device 250. Further, the operation unit may be an independent device.

  In addition, although it is preferable that the first display area and the second display area are interlocked and displayed in the same place, range, and dynamic range, they may be adjusted individually. The image processing required for such adjustment may be performed by an image data output module.

  In addition, the signal processing device 250 and the display device 280 may be integrally provided.

230 object 240 acoustic wave detector 250 signal processing device 252 image data acquisition module 253 image data output module 280 display device

Claims (20)

An image data acquisition unit for acquiring image data indicating a distribution of optical characteristic values of the subject obtained based on a detection signal of a photoacoustic wave generated by irradiating the subject with light;
Area information acquiring means for acquiring first area information indicating a first confidence area corresponding to the area sufficiently irradiated with the light inside the subject;
Image data output means for causing display means to display the image data, an image showing the first confidence region, and operation means capable of accepting an input from the operator based on the image data and the first area information When,
Processing equipment characterized by having. A light quantity distribution acquiring unit for acquiring a light quantity distribution of the light irradiated to the subject within the subject;
The area information acquisition means acquires the first area information in which the area in which the light quantity is included in a predetermined numerical range in the light quantity distribution is the first confidence area. Processing apparatus as described. A light quantity distribution acquiring unit for acquiring a light quantity distribution of the light irradiated to the subject within the subject;
The said area | region information acquisition means acquires the said 1st area | region information which made the said 1st reliability area the area | region whose light quantity is more than a predetermined | prescribed threshold value among the said light quantity distribution, It is characterized by the above-mentioned. Processing unit. The processing apparatus according to any one of claims 1 to 3, wherein the image data output unit causes the display unit to display the image data and an image indicating the first confidence region in a superimposed manner. . The process according to any one of claims 1 to 4, wherein the image data output means causes the display means to display the image data and an image indicating the first confidence region in different colors. apparatus. A light quantity distribution acquiring unit for acquiring a light quantity distribution of the light irradiated to the subject within the subject;
The processing device according to any one of claims 1 to 5, wherein the image data acquisition unit acquires the image data based on the detection signal of the photoacoustic wave and the light quantity distribution. The processing apparatus according to any one of claims 1 to 6, wherein the image data output unit causes the display unit to display a line indicating the first confidence region and the image data in an overlapping manner. . The processing device according to any one of claims 1 to 7, wherein the image data acquisition unit acquires an initial sound pressure, a light absorption coefficient, or a distribution of oxygen saturation as the image data. The image data output unit changes at least one of transparency, color, and gradation of an image displayed on the display unit based on input information from the user by the operation unit. The processor according to any one of 1 to 8. A processing device according to any one of the preceding claims,
A light source generating the light;
Detection means for acquiring the detection signal by detecting the photoacoustic wave;
An object information acquiring apparatus characterized by having: Acquiring image data indicating a distribution of optical characteristic values of the subject obtained based on a detection signal of a photoacoustic wave generated by irradiating the subject with light;
Acquiring first area information indicating a first confidence area corresponding to an area sufficiently irradiated with the light inside the subject;
Displaying, on a display means, the image data, an image indicating the first confidence region, and an operation means capable of receiving an input from an operator based on the image data and the first area information;
Processing method characterized by having. Acquiring a light quantity distribution of the light irradiated to the subject inside the subject;
In the step of acquiring the first area information, the first area information is acquired with the area having a light quantity included in a predetermined numerical range in the light quantity distribution as the first confidence area. The processing method according to claim 11. Acquiring a light quantity distribution of the light irradiated to the subject inside the subject;
In the step of acquiring the first area information, the first area information is acquired by setting an area having a light amount equal to or more than a predetermined threshold in the light quantity distribution as the first reliability area. The processing method according to claim 11. The process according to any one of claims 11 to 13, wherein in the step of displaying on the display means, the image data and an image showing the first confidence region are superimposed and displayed on the display means. Processing method. The process according to any one of claims 11 to 14, wherein in the step of displaying on the display means, the image data and the image showing the first confidence region are displayed on the display means in different colors. How to handle Acquiring a light quantity distribution of the light irradiated to the subject inside the subject;
The process according to any one of claims 11 to 15, wherein, in the step of acquiring the image data, the image data is acquired based on the detection signal of the photoacoustic wave and the light amount distribution. Method. The process according to any one of claims 11 to 16, wherein in the step of displaying on the display means, a line indicating the outer periphery of the first confidence region and the image data are superimposed and displayed on the display means. Processing method described. The processing method according to any one of claims 11 to 17, wherein in the step of acquiring the image data, a distribution of initial sound pressure, light absorption coefficient, or oxygen saturation is acquired as the image data. . 19. The apparatus according to any one of claims 11 to 18, wherein the operation means is capable of receiving an input for changing at least one of transparency, color, and shade of an image displayed on the display means. Processing method described in Section.   A program for causing a computer to execute the processing method according to any one of claims 11 to 19.

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