JP2017144047A - Imaging apparatus and driving method therefor, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mechanism capable of determining the reliability of a blood flow information cross-sectional image when the blood flow information cross-sectional image is generated using an optical coherence tomographic image of a substantially identical cross-section of a measurement object in which a blood vessel exists.SOLUTION: A correlation degree between each individual optical coherence tomographic image of an optical coherence tomographic image group 802 in a substantially identical cross section of a measurement target in which a blood vessel exists is calculated to select a high-correlation optical coherence tomographic image with a correlation degree equal to or greater than a predetermined threshold value from the optical coherence tomographic image group 802. A blood flow information cross-sectional image 805 is then generated using the selected optical coherence tomographic image, and a reliability index of the blood flow information cross-sectional image 805 is determined based on the selected optical coherence tomographic image.SELECTED DRAWING: Figure 8

Description

  The present invention relates to an imaging apparatus that performs imaging using optical coherence tomography, a driving method thereof, and a program for causing a computer to execute the driving method.

  Optical coherence tomography (hereinafter referred to as “OCT”) has been put into practical use as a method for non-destructively and non-invasively acquiring a tomographic image of a measurement target such as a living body. An imaging apparatus (hereinafter referred to as an “OCT apparatus”) that performs imaging using OCT is widely used particularly in the case of obtaining a tomographic image of the retina on the fundus of the eye to be examined in the ophthalmic region and performing ophthalmic diagnosis of the retina. It's being used.

  In this OCT apparatus, the tomographic image of the measurement target is obtained by causing the light reflected from the measurement target to interfere with the reference light and analyzing the time dependence or wave number dependence of the intensity of the interfered light. Examples of such an OCT apparatus include a time domain OCT apparatus that obtains depth information of a measurement object by changing the position of a reference mirror, and a spectral domain OCT (Spectral Domain OCT using a broadband light source: hereinafter, “SD-OCT”. And a swept source optical coherence tomography (hereinafter referred to as “SS-OCT”) device using a tunable light source device capable of changing the oscillation wavelength as a light source. . SD-OCT and SS-OCT are collectively referred to as FD-OCT (Fourier Domain OCT).

  In recent years, angiography using FD-OCT has been proposed, which is called OCT Angiography (hereinafter referred to as “OCTA”).

  Fluorescence contrast, which is a common angiography method in modern clinical medicine, requires injection of a fluorescent dye (for example, fluorescein or indocyanine green) into the body, and displays blood vessels that pass through the fluorescent dye in two dimensions. Is. However, there may be side effects on the contrast agent, nausea, rash, coughing, and in rare cases shock symptoms, and this fluorescence imaging is risky. On the other hand, OCTA enables angiography non-invasively and can display a blood vessel network three-dimensionally. Furthermore, OCTA attracts attention because it can depict microvessels when, for example, the measurement target is the fundus of the subject's eye.

  As for this OCTA, a plurality of methods have been conventionally proposed due to the difference in the detection method of the blood vessel region. For example, Patent Literature 1 and Patent Literature 2 propose a method using intensity variation due to blood flow. Further, for example, Patent Document 3 proposes a method that utilizes changes in phase and intensity due to blood flow.

US Patent Application Publication No. 2014/0228681 US Patent Application Publication No. 2014/0221827 U.S. Pat. No. 8,433,393

  OCTA is a technique for identifying a blood vessel region by repeatedly photographing substantially the same cross section of a measurement target and extracting a difference in signals acquired between the respective photographings. In order to generate a blood flow information cross-sectional image, at least two or more optical coherence tomographic images having substantially the same cross-section are required. Therefore, positional accuracy for each imaging is important. However, in order to generate three-dimensional blood flow information, a plurality of volume data of optical coherence tomographic images must be acquired (that is, a plurality of blood flow information cross-sectional images in a plurality of cross sections must be acquired). As time increases, it is difficult to obtain an image with stable fixation when the subject to be measured is the eye to be examined.

  For example, when acquiring an optical coherence tomographic image of substantially the same cross-section of the eye to be measured, when obtaining an optical coherence tomographic image with poor correlation (low correlation) due to poor fixation or blinking, usually The optical coherence tomographic image is discarded, and a blood flow information cross-sectional image is generated using another optical coherence tomographic image. Therefore, it is difficult to acquire the same number of optical coherence tomographic images in substantially the same cross section to be acquired in each cross section. That is, it is not always possible to generate a plurality of blood flow information sectional images for generating three-dimensional blood flow information from the same number of optical coherence tomographic images, and the number of optical coherence tomographic images to be used may differ depending on each cross section. is there. In general, the smaller the number of optical coherence tomographic images used, the lower the accuracy of blood vessel extraction in the blood flow information cross-sectional image (the reliability of the blood flow information cross-sectional image will decrease). Until now, there has been no reliability index indicating how many optical coherence tomographic images are composed of blood flow information cross-sectional images. Similarly, there is no index indicating a reliability index of the generated three-dimensional blood flow information.

  In Patent Document 1, a substantially identical cross section of a measurement target is scanned a plurality of times, an OCT interference signal is divided into M spectrum bands, an optical coherence tomographic image is generated from the divided spectrum, and correlation between optical coherence tomographic images is obtained. A technique for obtaining blood flow information by obtaining a value is described. However, Patent Document 1 does not consider the reliability of blood flow information.

  Also, in other Patent Documents 2 to 3, a method for generating blood flow information is described, but the reliability of blood flow information is not considered as in Patent Document 1.

  That is, in the conventional technology, when generating a blood flow information cross-sectional image using an optical coherence tomographic image in a substantially identical cross section of a measurement target in which a blood vessel exists, a highly reliable blood flow information cross-sectional image is generated. In addition, there is a problem that it is difficult to grasp the reliability.

  The present invention has been made in view of such problems, and grasps its reliability when generating a blood flow information cross-sectional image using a tomographic image at a substantially identical cross-section of a measurement target in which a blood vessel exists. The purpose is to provide a mechanism that can do this.

The imaging apparatus of the present invention is an imaging apparatus that performs imaging using optical coherence tomography, based on imaging means for repeatedly imaging substantially the same cross section of a measurement target in which blood vessels are present, and repeated imaging by the imaging means. A first generating unit that generates a plurality of tomographic images in the substantially same cross section; a calculating unit that calculates a degree of correlation of each tomographic image in the plurality of tomographic images; and the correlation among the plurality of tomographic images. A selection unit that selects a tomographic image having a degree equal to or higher than a predetermined threshold; a second generation unit that generates a blood flow information cross-sectional image in the substantially same cross section using the tomographic image selected by the selection unit; 1st determination means which determines the 1st reliability parameter | index which is a parameter | index which shows the reliability of the said blood-flow information cross-sectional image based on the tomographic image selected by the said selection means.
The present invention also includes a driving method for the above-described photographing apparatus and a program for causing a computer to execute the driving method.

  According to the present invention, when a blood flow information cross-sectional image is generated using a tomographic image in a substantially identical cross-section of a measurement target in which a blood vessel exists, the reliability can be grasped. Furthermore, according to the present invention, when generating three-dimensional blood flow information using a plurality of blood flow information cross-sectional images, the reliability can be grasped.

It is a figure which shows an example of schematic structure of the imaging device which concerns on embodiment of this invention. It is a figure which shows an example of the imaging | photography screen displayed on a display part at the time of imaging | photography of the imaging device which concerns on embodiment of this invention. It is a figure for demonstrating an example of the scan pattern in imaging | photography of the imaging device which concerns on embodiment of this invention. It is a flowchart which shows the drive method of the imaging device which concerns on embodiment of this invention, and shows an example of the specific process sequence of an interference signal acquisition process. 5 is a flowchart illustrating an example of a specific signal processing procedure of an interference signal, illustrating a method for driving an imaging device according to an embodiment of the present invention. It is a figure which shows embodiment of this invention and shows an example of the segmentation result in FIG.5 S216. It is a figure which shows embodiment of this invention and shows an example of the en-face image of OCTA produced | generated in step S217 of FIG. It is a figure which shows embodiment of this invention and shows an example of the display method of the 1st reliability parameter | index in a blood-flow information cross-sectional image, and the 2nd reliability parameter | index in three-dimensional blood-flow information. It is a figure which shows embodiment of this invention and shows an example of the display in the en-face image of OCTA. It is a figure which shows embodiment of this invention and shows an example of the OCTA imaging | photography result screen displayed on a display part. The embodiment of this invention is shown, and an example of a display of the 1st reliability parameter | index in the blood-flow information cross-sectional image which concerns on each cross-section corresponding to each site | part corresponding to each site | part of the said three-dimensional blood flow information is shown. FIG.

  Hereinafter, embodiments (embodiments) for carrying out the present invention will be described with reference to the drawings.

[Schematic configuration of the camera]
FIG. 1 is a diagram illustrating an example of a schematic configuration of a photographing apparatus 100 according to an embodiment of the present invention. Here, the imaging apparatus 100 according to the present embodiment is an imaging apparatus (OCT apparatus) that performs imaging using optical coherence tomography (OCT). Specifically, for example, an SD-OCT apparatus or an SS-OCT apparatus can be applied as the imaging apparatus 100 according to the present embodiment, but an SS-OCT apparatus is used as the imaging apparatus 100 described below. An example of application will be described. In the following description, an example in which the fundus oculi Er of the eye E is applied as a measurement target with blood vessels will be described. However, the present invention is not limited to this, and the measurement target with blood vessels is used. Any one is applicable. FIG. 1 also shows the crystalline lens El of the eye E.

  As shown in FIG. 1, the imaging apparatus 100 according to the present embodiment includes a wavelength swept light source 11, an SLO light source 12 for a scanning laser opthalmoscope (hereinafter referred to as “SLO”), and an OCT interference unit 20. , Detection unit 30, computer 40, measurement arm 50, reference arm 60, display unit 70, SLO optical system 80, anterior ocular segment imaging unit 90, dichroic mirror 105, objective lens 106, illumination light source 107, and internal fixation lamp 110.

  The wavelength swept light source 11 is a light source in which the frequency of emitted light is swept. The SLO light source 12 is not an indispensable light source in the photographing apparatus 100 according to the present embodiment, but is provided for acquiring an SLO image.

  The OCT interference unit 20 is configured to generate interference light. The detection unit 30 is configured to detect the interference light generated by the OCT interference unit 20. The computer 40 comprehensively controls driving in the photographing apparatus 100 and performs various types of information processing. For example, the computer 40 acquires information about the fundus Er of the eye E based on the interference light detected by the detection unit 30. The display unit 70 is based on the control of the computer 40. Various information and various images are displayed.

  The SLO optical system 80 is configured to obtain reflected light from the fundus Er of the eye E. The anterior segment imaging unit 90 is configured to capture the anterior segment of the eye E.

<Configuration of OCT measurement system>
The OCT interference unit 20 includes couplers 21 and 22.
First, the coupler 21 branches the light emitted from the wavelength swept light source 11 into measurement light and reference light that irradiates the fundus Er of the eye E to be examined. Here, in this example, the branching ratio is about 2: 8, and measurement light: reference light = 2: 8.

  The measurement light branched by the coupler 21 is irradiated to the fundus Er of the eye E via the measurement arm 50. More specifically, the measurement light incident on the measurement arm 50 is adjusted in polarization state by the polarization controller 51 and then emitted from the collimator 52 as spatial light. Thereafter, the measurement light passes through the X scanning scanner 53, the lenses 54 and 55, the Y scanning scanner 56, the dichroic mirror 103, the lens 57, the focus lens 58 fixed to the focus stage 59, and the objective lens 106. The fundus Er is irradiated. The X scanning scanner 53 and the Y scanning scanner 56 are scanning means having a function of scanning the fundus Er of the eye E with the measurement light. By this scanning means, the irradiation position of the measurement light onto the fundus Er can be changed. The dichroic mirror 103 has a characteristic of reflecting light having a wavelength of 1000 nm to 1100 nm and transmitting other light. Then, the backscattered light (reflected light) from the fundus Er of the eye E is again emitted from the measurement arm 50 along the optical path described above. Then, the light enters the coupler 22 via the coupler 21. At this time, 80% of the return light from the fundus Er is guided to the coupler 22 in accordance with the branching ratio described above.

  On the other hand, the reference light branched by the coupler 21 enters the coupler 22 via the reference arm 60. More specifically, the reference light incident on the reference arm 60 is adjusted in the polarization state by the polarization controller 61 and then emitted from the collimator 62 as spatial light. Thereafter, the reference light passes through the dispersion compensation glass 63, the optical path length adjustment optical system 64, and the dispersion adjustment prism pair 65, enters the optical fiber via the collimator lens 66, exits from the reference arm 60, and enters the coupler 22.

  The reflected light of the eye E that has passed through the measurement arm 50 at the coupler 22 interferes with the reference light that has passed through the reference arm 60. Then, the interference light is detected by the detection unit 30. The detection unit 30 includes a differential detector 31 and an A / D converter 32.

  First, in the detection unit 30, the interference light that has been demultiplexed immediately after the interference light is generated by the coupler 22 is detected by the differential detector 31. Then, the OCT interference signal converted into the electric signal by the differential detector 31 is converted into a digital signal by the A / D converter 32. Here, in the imaging apparatus 100 of FIG. 1, sampling of the interference light is performed at equal optical frequency (equal wave number) intervals based on the k clock signal transmitted from the k clock generation unit incorporated in the wavelength swept light source 11. Is called. The digital signal output from the A / D converter 32 is sent to the computer 40.

  The above is an acquisition process of information regarding a tomography at a certain point of the eye E, and acquiring information regarding a tomography in the depth direction of the eye E in this way is referred to as “A-scan”. In addition, the information about the tomography of the eye E in the direction orthogonal to the A-scan, that is, the scanning direction for acquiring the two-dimensional image is “B-scan”, and any one of the scanning directions of A-scan and B-scan Scanning in a direction orthogonal to both is called “C-scan”. This is because, when acquiring a three-dimensional tomographic image, when performing two-dimensional raster scanning within the fundus Er, the high-speed scanning direction is B-scan, and the low-speed scanning direction is performed by scanning the B-scan in the orthogonal direction. Becomes C-scan. A two-dimensional tomographic image is obtained by performing A-scan and B-scan, and a three-dimensional tomographic image is obtained by performing A-scan, B-scan, and C-scan. B-scan and C-scan are performed by the X scanning scanner 53 and the Y scanning scanner 56 described above.

  Note that each of the X scanning scanner 53 and the Y scanning scanner 56 is configured by a deflecting mirror disposed so that the rotation axes thereof are orthogonal to each other. The X scanning scanner 53 performs scanning in the X axis direction, and the Y scanning scanner 56 performs scanning in the Y axis direction. The X-axis direction and the Y-axis direction are directions perpendicular to the eye axis direction of the eyeball of the eye E and are perpendicular to each other. Further, the line scanning direction such as B-scan and C-scan may not coincide with the X-axis direction or the Y-axis direction. For this reason, the B-scan and C-scan line scanning directions can be appropriately determined according to a two-dimensional tomographic image or a three-dimensional tomographic image to be photographed.

<Configuration of SLO measurement system>
The light emitted from the SLO light source 12 is applied to the fundus Er of the eye E through the SLO optical system 80. More specifically, the light incident on the SLO optical system 80 is emitted from the collimator 81 to the space as parallel light. Thereafter, it passes through the perforated part of the perforated mirror 101 and reaches the dichroic mirror 102 via the lens 82, the X scanning scanner 83, the lenses 84 and 85, and the Y scanning scanner 86. Note that the X scanning scanner 83 and the Y scanning scanner 86 are examples of SLO scanning means, and the OCT X scanning scanner 53 and the Y scanning scanner 56 may be configured as a common XY scanning scanner. The dichroic mirror 102 has a characteristic of reflecting light of 760 nm to 800 nm and transmitting other light. The light reflected by the dichroic mirror 102 reaches the fundus Er of the eye E through an optical path similar to that in the OCT measurement system.

  The measurement light irradiated on the fundus Er of the eye E is reflected and scattered by the fundus Er, and reaches the perforated mirror 101 along the optical path described above. The light reflected by the perforated mirror 101 is received by an avalanche photodiode (hereinafter referred to as “APD”) 88 through a lens 87, converted into an electrical signal, and sent to the computer 40. Here, the position of the perforated mirror 101 is conjugate with the pupil position of the eye to be examined Er, and the pupil peripheral part of the eye to be examined E out of the light reflected and scattered by the measurement light irradiated on the fundus Er. The light passing therethrough is reflected by the perforated mirror 101.

<Configuration of anterior segment measurement system>
The anterior ocular segment measurement system irradiates the anterior ocular segment of the eye E with an illumination light source 107 including an LED that emits illumination light having a wavelength of about 860 nm. The light reflected by the anterior segment of the eye E reaches the dichroic mirror 105 via the objective lens 106. The dichroic mirror 105 has a characteristic of reflecting light of 820 nm to 920 nm and transmitting other light. The light reflected by the dichroic mirror 105 is received by the anterior eye camera 94 through the lenses 91, 92, and 93 of the anterior eye photographing unit 90. The light received by the anterior eye camera 94 is converted into an electrical signal and sent to the computer 40.

<Internal fixation lamp 110>
The internal fixation lamp 110 includes an internal fixation lamp display unit 111 and a lens 112. As the internal fixation lamp display unit 111, a display in which a plurality of light emitting diodes (LD) are arranged in a matrix is used. The lighting position of the light emitting diode is changed in accordance with the part to be photographed. The light from the internal fixation lamp display unit 111 is guided to the eye to be examined Er via the lens 112. The light emitted from the internal fixation lamp display unit 111 is about 520 nm, and a set desired pattern is displayed.

<Computer 40>
The computer 40 processes the interference signal converted into a digital signal, and generates a front image including the above-described optical coherence tomographic image, blood flow information cross-sectional image, three-dimensional blood flow information, so-called en-face image. Here, the computer 40 that performs the process of generating the optical coherence tomographic image constitutes a first generation unit. In addition, the computer 40 that performs the process of generating the blood flow information cross-sectional image constitutes a second generation unit. The computer 40 that performs the process of generating the three-dimensional blood flow information constitutes a third generation unit. The computer 40 that performs the process of generating the front image constitutes a fourth generation unit. Details of specific signal processing performed by the computer 40 will be described later.

  Further, the computer 40 processes the fundus signal of the SLO converted into the digital signal sent from the APD 88, and generates an SLO image. In addition, the computer 40 processes a signal sent from the anterior eye camera 94 and generates an anterior eye image.

  Information such as an optical coherence tomographic image, blood flow information cross-sectional image, three-dimensional blood flow information, front image, SLO image, and anterior eye image obtained as a result of signal processing by the computer 40 is displayed by the display unit 70. The

[OCTA scan area setting]
FIG. 2 is a diagram illustrating an example of a shooting screen 200 displayed on the display unit 70 during shooting by the shooting apparatus 100 according to the embodiment of the present invention. An anterior ocular segment image 202, an SLO image (fundus image) 203 and an optical coherence tomographic image 206 generated by the computer 40 are displayed in the display area 201 of the imaging screen 200.

  First, based on the anterior segment image 202, the imaging apparatus 100 is aligned with the eye E to be examined in the optical axis direction of the measurement light. At this time, the alignment may be performed manually by the examiner or automatically by the computer 40 while recognizing the anterior segment image 202.

  Next, focus adjustment is performed so that the SLO image 203 is optimized. At this time, the focus adjustment may be performed manually by the examiner using the focus adjustment unit 205, or may be automatically performed by the computer 40 based on the SLO image 203.

  In addition, the OCTA scan area can be specified by, for example, the guide 204 displayed on the SLO image 203 that is a fundus image. The guide 204 can be set to an arbitrary size, shape, and position. For example, a 6 mm × 6 mm square, a radial pattern inscribed in a circle with a diameter of 5 mm, a line pattern of 16 mm, and the like can be selected. For example, the computer 40 displays an arbitrary tomographic image of the OCTA scan area designated by the guide 204 as the optical coherent tomographic image 206.

  Thereafter, gate adjustment is performed so that the optical coherence tomographic image 206 is optimized. At this time, the gate adjustment may be manually performed by the examiner using the gate adjustment unit 207, or may be automatically performed by the computer 40 based on the optical coherence tomographic image 206.

[Scan Pattern]
FIG. 3 is a diagram for explaining an example of a scan pattern in photographing by the photographing apparatus 100 according to the embodiment of the present invention.
In OCTA, since the time change of the OCT interference signal due to blood flow is measured, multiple measurements are required at the same location of the measurement target where the blood vessel exists. In imaging by the imaging apparatus 100 according to the present embodiment, a scan that moves to n Y positions is performed while repeating B scans at the same location of the measurement target where blood vessels exist, m times. FIG. 3 shows this specific scan pattern.

  As illustrated in FIG. 3, the imaging apparatus 100 according to the present embodiment repeatedly performs B scans m times each for n Y positions y1 to yn on the fundus plane. At this time, if the value of m is large, the number of times of measurement at the same place increases, so that blood flow detection accuracy is improved. On the other hand, the scan time becomes long, and there arises a problem that motion artifacts are generated in the image due to the movement of the eye E during the scan (fixation fine movement) and a problem that the burden on the subject increases. In this embodiment, m = 5 is performed in consideration of the balance between the two. Note that the value of m may be freely changed and set according to the A scan speed of the imaging apparatus 100 and the amount of movement of the eye E.

  In FIG. 3, p indicates the number of samplings of A scan in one B scan. That is, the plane image size is determined by p × n. If p × n is large, scanning can be performed over a wide range at the same measurement pitch, but on the other hand, the scanning time becomes long, and the above-mentioned problem of motion artifacts and the burden on the subject increase. In FIG. 3, Δx is an interval between adjacent X positions (x pitch), and Δy is an interval between adjacent Y positions (y pitch). In the present embodiment, the x pitch indicated by Δx in FIG. 3 is set as ½ of the beam spot diameter (fundus beam spot diameter) of the irradiation light on the fundus Er, for example, 10 μm. At this time, even if the x pitch is made smaller than ½ of the fundus beam spot diameter, the effect of increasing the definition of the generated image is small. Further, the y pitch indicated by Δy in FIG. 3 is set to 20 μm, for example, in order to shorten the scan time.

  Regarding the x pitch and the y pitch, when the fundus beam spot diameter is increased, the definition deteriorates, but a wide range of images can be acquired with a small data capacity. The x pitch and y pitch may be freely changed and set according to clinical requirements.

[Interference signal acquisition procedure]
FIG. 4 is a flowchart illustrating an example of a specific processing procedure of the interference signal acquisition process, which illustrates the driving method of the imaging apparatus 100 according to the embodiment of the present invention.

  First, in step S101, the computer 40 defines (sets) the index i of the position yi shown in FIG.

  Subsequently, in step S102, the computer 40 performs control to move the scan position to the position yi and start the X scan.

  Subsequently, in step S103, the computer 40 defines (sets) an index j of repeated B-scans corresponding to repeated imaging of substantially the same cross section of the measurement target in which blood vessels are present.

  Subsequently, in step S104, the computer 40 sets the number of repeated B scans to m.

  Subsequently, in step S105, the computer 40 performs control to acquire a B scan signal. Specifically, when the differential detector 31 detects an interference signal for each A scan, the computer 40 acquires the interference signal via the A / D converter 32. The computer 40 acquires the p-sample interference signal for the A scan, and sets this as an interference signal for one B scan.

  Subsequently, in step S106, the computer 40 determines whether or not the index j has reached a predetermined number (m). That is, it is determined whether or not the B scan at the position yi has been repeated m times. As a result of the determination, if the index j has not reached the predetermined number (m) and the B scan at the position yi has not yet been repeated m times, the process returns to step S104 and the index B of the repeated B scan is set. After incrementing, the process proceeds to step S105.

On the other hand, as a result of the determination in step S106, if the index j reaches the predetermined number (m) and the B scan at the position yi is repeated m times, the process proceeds to step S107.
In step S107, the computer 40 determines whether or not the index i has reached a predetermined number (n) of measurement lines, that is, determines whether or not a B scan has been performed at all y positions. . As a result of this determination, if the index i has not reached the predetermined number of measurement lines (n), the process returns to step S102, the index i of the position yi is incremented, and then the process proceeds to step S103.

On the other hand, as a result of the determination in step S107, if the index i has reached a predetermined number of measurement lines (n), the process proceeds to step S108.
In step S108, the computer 40 performs control to acquire background data. Specifically, the photographing apparatus 100 measures, for example, 100 A scans with the shutter 104 closed, and the computer 40 averages and stores data obtained by the 100 A scans. The number of background measurements is not limited to 100 times.

  When the process of step S108 ends, the process of the flowchart of FIG. 4 related to the interference signal acquisition process ends.

[Signal processing procedure]
FIG. 5 is a flowchart illustrating an example of a specific signal processing procedure for an interference signal, illustrating a method for driving the imaging apparatus 100 according to the embodiment of the present invention. Specifically, FIG. 5 shows that the computer 40 to which the interference signal is input obtains three-dimensional blood flow information as a result of signal processing of the interference signal, and an en-face image (hereinafter referred to as “OCTA_en−”) of the blood flow information. 5 is a flowchart until the output of “face image”. The en-face image here is an image that two-dimensionally represents a specific retinal layer of the eye E.

  In the present embodiment, it is necessary to calculate a motion contrast feature amount in order to generate an OCTA en-face image. Here, the motion contrast is defined as a contrast between a tissue having a flow (for example, blood) and a tissue having no flow in the subject tissue. Then, a feature amount expressing the motion contrast is defined as a motion contrast feature amount. This motion contrast feature amount will be described later.

Hereinafter, the description of FIG. 5 will be given.
First, in step S201, the computer 40 defines (sets) the index i of the position yi shown in FIG.

  Subsequently, in step S202, the computer 40 performs a process of extracting interference signals (for m sheets) by repeated B scans at the position yi.

  Subsequently, in step S203, the computer 40 repeatedly defines (sets) an index j for B scan.

  Subsequently, in step S204, the computer 40 performs a process of extracting the j-th B scan data.

  Subsequently, in step S205, the computer 40 subtracts the background data acquired in step S108 of FIG. 4 from the above-described interference signal.

  Subsequently, in step S206, the computer 40 performs a Fourier transform on the interference signal obtained by subtracting the background data in step S205. In this case, in the present embodiment, Fast Fourier Transform (FFT) is used.

  Subsequently, in step S207, the computer 40 calculates the square of the absolute value of the signal obtained by the Fourier transform executed in step S206. The value obtained by this calculation is the intensity of the tomographic image of the B scan.

  Subsequently, in step S208, the computer 40 determines whether or not the index j has reached a predetermined number (m). That is, it is determined whether or not the B-scan intensity calculation at the position yi has been repeated m times. As a result of the determination, if the index j has not reached the predetermined number (m) and the B-scan Intensity calculation at the position yi has not yet been repeated m times, the process returns to step S204, and at the same Y position. Repeat the B-scan Intensity calculation.

On the other hand, as a result of the determination in step S208, if the index j reaches the predetermined number (m) and the B-scan intensity calculation at the position yi is repeated m times, the process proceeds to step S209.
In step S209, the computer 40 calculates image similarity in m frames of repeated B scans at a certain position yi. Specifically, for example, the computer 40 selects an arbitrary frame from m frames of repeated B scans at a certain position yi as a template, and the remaining m−1 frames not selected as the template. The degree of correlation with is calculated. At this time, the degree of correlation in one frame selected as a template can be set to 100% (1.0), for example. In the above processing, one optical coherence tomographic image is selected from a plurality of optical coherence tomographic images on substantially the same cross section, and the one optical coherence tomographic image and the remaining optical coherence tomographic images not selected are selected. This is equivalent to calculating the correlation degree of each optical coherence tomographic image by calculating the correlation degree. At this time, the computer 40 may perform a layer recognition process for recognizing a layer for each optical coherence tomographic image, and calculate a correlation degree based on the recognition result of the layer.

  Subsequently, in step S210, the computer 40 determines that the correlation degree is a predetermined threshold value from m frames (a plurality of optical coherence tomographic images) of repeated B scan at a certain position yi based on the correlation value calculated in step S209. The above highly correlated frame (optical coherence tomographic image) is selected. At this time, the predetermined threshold value can be arbitrarily set, but is set so as to be able to remove a frame whose correlation as an image has decreased due to the subject's blinking or fixation micromotion.

  As described above, OCTA is a technique for distinguishing the contrast between a flowable tissue (for example, blood) and a flowless tissue among subject tissues based on a correlation value between images. That is, tissue with no flow is extracted based on the premise that the correlation between images is high, so if the correlation is low as an image, it becomes a false detection when calculating the motion contrast feature amount, as if the entire image Is judged as if it is a flowing organization. In this step 210, in order to avoid such erroneous detection, images with low correlation are removed in advance, and only images with high correlation are selected. As a result of this image selection, the m-frame images acquired at the same position yi are appropriately selected and become q-frame images. Here, a possible value of q is 1 ≦ q ≦ m.

  Subsequently, in step S211, the computer 40 aligns q frames with high correlation selected from m frames of repeated B scans at a position yi in step S210.

  Specifically, first, the computer 40 selects any one frame from the selected q frames as a template. Here, correlations may be calculated for all combinations of the selected q frames, the sum of correlation coefficients may be obtained for each frame, and the frame that maximizes the sum may be selected.

  Next, the computer 40 performs collation for each frame with the template to obtain the positional deviation amount (δX, δY, δθ). More specifically, the computer 40 calculates Normalized Cross-Correlation (NCC), which is an index representing similarity, while changing the position and angle of the template image, and calculates the difference in image position when this value is maximized. Obtained as the amount of displacement.

  In the present embodiment, the index representing the similarity can be variously changed as long as it is a scale representing the similarity between the template and the image feature in the frame. For example, Sum of Absolute Difference (SAD), Sum of Squared Difference (SSD), Zero-means Normalized Cross-Correlation (ZNCC), Phase Only Correlation (POC), Phase Only Correlation (POC) .

  Next, the computer 40 applies position correction to q−1 frames other than the template in accordance with the positional deviation amounts (δX, δY, δθ), and performs q frame alignment. If q is 1, the process of step S211 is not executed.

  When the process of step S211 is completed, the process proceeds to steps S212 and S213.

  In step S212, the computer 40 calculates a motion contrast feature amount. In the present embodiment, the computer 40 calculates a variance value for each pixel at the same position between q intensity frames selected in step S210 and aligned in step S211, and calculates the variance value as a motion contrast feature. Amount. There are various methods for obtaining the motion contrast feature amount. In this embodiment, the motion contrast feature amount is an index that represents a change in the luminance value of each pixel of a plurality of B-scan images at the same Y position. Applicable. Also, when q = 1, that is, when the correlation is low as an image due to the effects of blinking or fixation micromotion, and it is impossible to calculate the motion contrast feature quantity at the same position yi, different processing is performed. . For example, this step may be ended by setting the motion contrast feature amount to 0, or when the motion contrast feature amount in the images yi−1 and yi + 1 before and after the position yi is obtained, interpolation is performed from the dispersion values before and after the step yi. A motion contrast feature amount may be obtained. In this case, the feature quantity that could not be calculated correctly can be used as an evaluation index of reliability described later by notifying that the feature value is an interpolation value. Alternatively, the Y position where the feature amount could not be calculated may be stored, and rescanning may be performed automatically. Alternatively, a warning prompting remeasurement may be issued without performing automatic rescanning.

  In step S213, the computer 40 averages the intensity images aligned in step S211 and generates an intensity averaged image.

When the processes of steps S212 and S213 are completed, the process proceeds to step S214.
In step S214, the computer 40 performs threshold processing on the motion contrast feature amount calculated in step S212. In the present embodiment, the threshold used for the threshold processing is extracted from the intensity averaged image generated in step S213 by extracting an area where only random noise is displayed on the noise floor, calculating the standard deviation σ, Set the value of average floor brightness + 2σ. The computer 40 sets the value of the motion contrast feature amount corresponding to the area where each intensity is equal to or less than the threshold value to 0. Noise can be reduced by removing the motion contrast derived from the intensity change due to random noise by the threshold processing in step S214. Note that the smaller the threshold value used in the threshold processing in step S214, the higher the sensitivity of motion contrast detection and the more the noise component. Also, as the threshold value is larger, noise is reduced, but the sensitivity of motion contrast detection is lowered. In the present embodiment, the threshold is set as the average luminance of the noise floor + 2σ, but the threshold is not limited to this.

  Subsequently, in step S215, the computer 40 determines whether or not the index i has reached a predetermined number (n). That is, in all the Y positions of n locations, the image correlation calculation process (S209), the image selection process (S210), the alignment process (S211), the motion contrast feature quantity calculation process (S212), and the intensity averaged image generation process It is determined whether (S213) and threshold processing (S214) have been performed. If it is determined that the index i has not reached the predetermined number (n), the process returns to step S202.

On the other hand, if the index i reaches the predetermined number (n) as a result of the determination in step S215, the process proceeds to step S216. At this time, the intensity averaged image and the motion contrast feature amount three-dimensional volume data (three-dimensional blood flow information) in the B scan image at all the Y positions are acquired.
In step S216, the computer 40 performs segmentation of the retina of the eye E from the intensity averaged image generated in step S213, and generates segmentation data. The retina segmentation of the eye E will be specifically described below.

  The computer 40 generates an image by applying the median filter and the Sobel filter to the tomographic image to be processed extracted from the intensity averaged image (hereinafter referred to as “median image” and “Sobel image, respectively”). ”). Next, the computer 40 creates a profile for each A scan from the generated median image and Sobel image. Specifically, the median image has a luminance value profile, and the Sobel image has a gradient profile. Next, the computer 40 detects a peak in the profile created from the Sobel image. Next, the computer 40 extracts the boundary of each region of the retinal layer of the eye E by referring to the profile of the median image before and after the detected peak and between the peaks.

  FIG. 6 is a diagram illustrating an example of the segmentation result in step S216 in FIG. 5 according to the embodiment of this invention. FIG. 6 is an Intensity averaged image at a certain y position, and segmentation lines are overlaid with broken lines.

  In the example shown in FIG. 6, six layers are detected as a result of segmentation. The breakdown of the six layers is as follows: [1] nerve fiber layer (NFL), [2] ganglion cell layer (GCL) + inner plexus layer (IPL) combined layer, [3] inner granule layer (INL) + outer reticular shape Layer (OPL) combined layer, [4] outer granular layer (ONL) + outer boundary membrane (ELM) combined layer, [5] Ellipsoid Zone (EZ) + Interdigitation Zone (IZ) + retinal pigment epithelium (RPE) [6] Choroid. The segmentation described in the present embodiment is an example, and other methods such as segmentation using the Dijkstra method may be used. The number of layers to be detected can be arbitrarily selected.

Here, it returns to description of FIG. 5 again.
When the process of step S216 ends, the process proceeds to step S217.
In step S217, the computer 40 generates an OCTA en-face image based on the segmentation data generated in step S216. Specifically, the computer 40 determines an area corresponding to, for example, a layer combining [2] ganglion cell layer (GCL) + inner reticulated layer (IPL) shown in FIG. The representative value of the motion contrast feature value is determined for each A scan. Here, the average value, the maximum value, and the median value may be determined as the representative value for the A scan. By plotting the representative values for this A-scan two-dimensionally (X direction, Y direction), a layer combining [2] ganglion cell layer (GCL) + inner plexus layer (IPL) shown in FIG. A corresponding OCTA en-face image is generated.

  FIG. 7 is a diagram illustrating an embodiment of the present invention and an example of an OCTA en-face image generated in step S217 of FIG. Specifically, FIG. 7 is obtained by measuring the macular portion of the eye E with the imaging apparatus 100. In this example, a segmented data is combined from [2] ganglion cell layer (GCL) + inner plexiform layer (IPL) shown in FIG. 6 to generate an OCTA en-face image, and the fundus blood vessel is depicted. doing. It should be noted that an OCTA en-face image of an arbitrary layer can be generated by selecting a layer from which the volume data of the motion contrast feature amount is extracted from the segmentation data.

  When the process of step S217 ends, the process of the flowchart of FIG. 5 related to the specific signal processing procedure of the interference signal ends.

[Decision and display of reliability index]
Next, a determination method and a display method of a first reliability index that is an index indicating the reliability of the blood flow information cross-sectional image and a second reliability index that is an index indicating the reliability of the three-dimensional blood flow information Will be described.

  In this embodiment, as a result of calculating the image correlation degree of the B scan at the same position (substantially the same cross section of the fundus Er of the eye E to be measured) in step S209 of FIG. An image having a low correlation degree as an image is excluded in step S210 and proceeds to a subsequent process. Since this process is performed at all scan positions, the number of optical coherence tomographic images for calculating the motion contrast feature amount of the blood flow information cross-sectional image differs for each scan position. As described above, there are various methods for obtaining the motion contrast feature amount, but any index can be applied as long as it is an index that represents a change in the luminance value of each pixel of a plurality of B scan images at the same Y position. In the present embodiment, between Intensity images, a variance value is calculated for each pixel at the same position, and the variance value is used as a motion contrast feature amount, but when the number of images used to calculate the variance value changes, The certainty of the obtained dispersion value changes. This is because, in general, the smaller the number of samples, the more the average value and variance value of the obtained data contain more errors than the true value. Therefore, in the present embodiment, when generating the blood flow information cross-sectional image, the first reliability index in the blood flow information cross-sectional image is determined using the number of used optical coherence tomographic images as a parameter.

  FIG. 8 is a diagram illustrating an example of a display method of the first reliability index in the blood flow information cross-sectional image and the second reliability index in the three-dimensional blood flow information according to the embodiment of the present invention. The contents shown in FIG. 8 are displayed on the display unit 70. Further, the first reliability index and the second reliability index shown in FIG. 8 are determined by the computer 40. The computer 40 that performs the process of determining the first reliability index constitutes a first determination means, and the computer 40 that performs the process of determining the second reliability index constitutes a second determination means. FIG. 8 shows an example in which both the first reliability index and the second reliability index are displayed. However, the present embodiment is not limited to this example. Any form that displays at least one of the reliability index and the second reliability index may be used.

  In FIG. 8, B scan image groups 801 to 803 are optical coherence tomographic image groups generated as a result of performing B scans m times at the same position (substantially the same cross section of the fundus Er of the eye E to be measured). It is. In the example shown in FIG. 8, the case of m = 5 is shown, but it is not always necessary that m = 5. Further, in FIG. 8, a B-scan image (optical coherence tomographic image) that is highly correlated indicates an image that has been selected in step S210 of FIG. . Further, in FIG. 8, the B scan image (optical coherence tomographic image) that is low correlated indicates an image that is not selected because it is determined in step S210 in FIG. 5 that the degree of correlation is not equal to or greater than a predetermined threshold value. .

  In FIG. 8, in the B-scan image group 801 and the B-scan image group 803, there is no influence of blinking or fixation micromotion, and all five optical coherence tomographic images can be acquired with high correlation at the same position. In this case, all five optical coherence tomographic images are used for calculating the motion contrast feature amount. Therefore, in the example illustrated in FIG. 8, the computer 40 trusts the blood flow information cross-sectional image 804 generated using the B-scan image group 801 and the blood flow information cross-sectional image 806 generated using the B-scan image group 803. The degree index (first reliability index) is set to 5, which is the number of B-scan image groups used for calculating the motion contrast feature amount.

  On the other hand, in the B scan image group 802, since two optical coherence tomographic images are excluded due to low correlation among the five optical coherence tomographic images, the blood flow information cross-sectional image generated from the B scan image group 802 The reliability index (first reliability index) of 805 is set to 3. Further, for example, when there is only a B scan image that has a low correlation in the B scan image group 802 due to the effect of blinking or fixation micromotion, and it is impossible to generate the blood flow information cross-sectional image 805, the proximity The blood flow information cross-sectional image may be generated by interpolating from the motion contrast feature amount at the B-scan part to be performed. In this case, an abnormality is notified that the blood flow information cross-sectional image that could not be correctly generated is an interpolation value, and, for example, the reliability index (first reliability index) is set to 1. In the present invention, the present invention is not limited to this mode. For example, the present invention corresponds to a case where the number of B scan images (optical coherence tomographic images) highly correlated in a certain B scan image group is less than a predetermined number. Based on the blood flow information cross-sectional image of a part of the B scan that is close to the part of the B scan and that has a high number of B scan images (optical coherence tomographic images) satisfying a predetermined number. A form of generating a blood flow information cross-sectional image of a scanned part is also included in the present invention.

  In the example shown in FIG. 8, the blood flow information cross-sectional image is displayed on the display unit 70 together with the reliability index (first reliability index) of each blood flow information cross-sectional image.

In the example shown in FIG. 8, the number of highly correlated B-scan images (optical coherence tomographic images) at the same position is applied as it is as the first reliability index. However, the present embodiment is not limited to this. It is not a thing. For example, as the first reliability index, the ratio of the number of B-scan images with high correlation to the number of B-scan images at the same position (the usage rate of B-scan images) may be applied. In any case, these aspects correspond to determining the first reliability index in the blood flow information cross-sectional image using the number of highly correlated B-scan images (optical coherence tomographic images).
In the present embodiment, in addition to determining the first reliability index using the number of the highly correlated B-scan images (optical coherence tomographic images), for example, the high correlation calculated in step S209 in FIG. It is also possible to apply a mode in which the first reliability index is determined using the degree of correlation in the B scan image (optical coherence tomographic image). In this case, various calculated values such as an average value and a total value of each correlation degree in the highly correlated B-scan image (optical coherence tomographic image) may be determined as the first reliability index in the blood flow information sectional image. it can.

  Thus, after calculating | requiring a 1st reliability parameter | index with respect to all the Y positions, the computer 40 uses the calculated | required 1st reliability parameter | index as the 2nd reliability in the three-dimensional blood-flow information 807. Determine the degree indicator. Here, the second reliability index in the three-dimensional blood flow information 807 uses a representative value of the first reliability index in the blood flow information cross-sectional images 804 to 806 at all Y positions. In the present embodiment, the average value of the first reliability index in all blood flow information cross-sectional images 804 to 806 is used as a representative value, but in addition to this, the median value or mode value is used. Also good.

  When the second reliability index in the three-dimensional blood flow information 807 is equal to or smaller than a predetermined threshold, the computer 40 determines that the measurement has failed and displays a warning for prompting remeasurement on the display unit 70. Aspects are also applicable to this embodiment. In the present embodiment, when the first reliability index is equal to or less than the predetermined threshold, the computer 40 determines that the measurement has failed and displays a warning prompting remeasurement on the display unit 70. Applicable.

In the present embodiment, the second reliability index in the three-dimensional blood flow information 807 may be determined as follows.
For example, the computer 40 generates an OCTA en-face image as a front image generated based on the selected optical coherence tomographic image, and extracts blood vessels from the OCTA en-face image. . In this case, a form in which the computer 40 determines the second reliability index in the three-dimensional blood flow information 807 based on the extracted blood vessel continuity is also applicable to this embodiment. A specific processing method of this form will be described below.

  The computer 40 determines the continuity of the image from the OCTA en-face image, and the continuity of the image at this time is whether or not the blood vessel which is a characteristic location in the OCTA en-face image is not discontinuous. This is done by detecting In addition, as a method for determining continuity using a feature location, for example, there is a method using normalized cross-correlation. In the case of this method, the computer 40 first calculates the luminance value per pixel of the OCTA en-face image, and acquires the luminance value profile for each line. Then, the computer 40 compares the acquired luminance value profile with the adjacent profiles, and calculates the similarity. In this case, the similarity is expressed between 0 and 1, and 1 means that they are completely matched. In addition, a threshold is set for the similarity, and if the similarity between adjacent lines is less than the threshold, it means that continuity is not maintained between the lines. -It can be seen that there are discontinuous parts in the face image. Although the method using normalized cross-correlation has been described here, the method is not limited to this method, and any method may be used as long as continuity is determined using a feature location. When the computer 40 determines that there are discontinuous portions in the OCTA en-face image, for example, the computer 40 sets a second confidence index in the three-dimensional blood flow information to 1 and issues a warning prompting remeasurement. It is displayed on the display unit 70. Further, when there is a discontinuous portion, the computer 40 displays a pointer 902 indicating the discontinuous portion side by side with the OCTA en-face image 901, for example, as shown in FIG. May be reduced.

  In the present embodiment, the front image generated based on the selected optical coherence tomographic image is not limited to the above-described OCTA en-face image, and the selected optical coherent tomographic image is the measurement target. It is also possible to apply an integrated image integrated in the depth direction.

  FIG. 10 is a diagram illustrating an example of the OCTA imaging result screen 1000 displayed on the display unit 70 according to the embodiment of this invention. A display area 1001 of the OCTA imaging result screen 1000 includes a mode selection tab 1002 for selecting a segmentation area. In the display area 1001, three-dimensional blood flow information of the retinal layer designated by the mode selection tab 1002 (specifically, an OCTA en-face image in which the three-dimensional blood flow information is two-dimensionally projected on the fundus). 1003 and a blood flow information cross-sectional image 1005 are displayed. In the display area 1001, as a marker for designating a part of three-dimensional blood flow information (specifically, an OCTA en-face image in which the three-dimensional blood flow information is two-dimensionally projected on the fundus). A corresponding guide 1004 is arranged, and an arbitrary Y position can be designated using this guide 1004 so that a blood flow information sectional image 1005 relating to a section corresponding to the region designated by the guide 1004 can be displayed. It has become. The guide 1004 is displayed as a line on the three-dimensional blood flow information (specifically, an OCTA en-face image obtained by projecting the three-dimensional blood flow information two-dimensionally on the fundus), for example, dragging with a mouse. In addition to specifying the Y coordinate by operation, it is also possible to directly specify the coordinate from a numerical value input unit arranged in the display area 1001.

  Further, the extracted blood vessel 1006 is displayed in the blood flow information cross-sectional image 1005. It should be noted that the blood vessel 1006 may be displayed superimposed on an intensity image or a segmentation line. Furthermore, in the display area 1001, a second reliability index 1007 in the three-dimensional blood flow information 1003 and a first reliability index 1008 in the blood flow information cross-sectional image 1005 are displayed on a scale. The user can evaluate the image while referring to these reliability indexes.

  Further, as shown in FIG. 11A, the first confidence index in each blood flow information cross-sectional image may be displayed using the color index along with the three-dimensional blood flow information. Specifically, FIG. 11A shows blood calculated at each Y position in accordance with an OCTA en-face image 1101 in which three-dimensional blood flow information is two-dimensionally projected onto the fundus and a color legend 1103 of a confidence index. It is the example which displayed the color parameter | index 1102 which shows the 1st reliability parameter | index in a flow information cross-sectional image.

  In addition, as shown in FIG. 11B, the first confidence index in each blood flow information cross-sectional image may be displayed using the color index so as to overlap the three-dimensional blood flow information. Specifically, FIG. 11B shows a blood flow information cross-sectional image calculated at each Y position on the OCTA en-face image 1101 according to the OCTA en-face image 1101 and the color legend 1103 of the confidence index. This is an example in which the first confidence index is superimposed and displayed as the color index 1104.

  Further, in the present embodiment, when determining the second reliability index in the three-dimensional blood flow information 1003, the number of sites where the number of selected optical coherence tomographic images is less than a predetermined number (for example, selected). Alternatively, the second reliability index may be determined based on the number of blood flow information cross-sectional images in which the number of optical coherence tomographic images is less than a predetermined number.

In the imaging apparatus 100 according to the embodiment of the present invention, the correlation degree of each optical coherence tomographic image of a plurality of optical coherence tomographic images in substantially the same cross section of the fundus Er (measurement target) of the eye E is calculated (S209 in FIG. 5). ), An optical coherence tomographic image having a correlation degree equal to or higher than a predetermined threshold is selected from the plurality of optical coherent tomographic images (210 in FIG. 5), and the selected one is selected based on the selected optical coherence tomographic image. The reliability index (first reliability index) of the blood flow information cross-sectional image generated using the optical coherence tomographic image is determined (FIG. 8 and the like).
According to this configuration, when generating a blood flow information cross-sectional image using an optical coherence tomographic image in a substantially same cross section of a measurement target in which a blood vessel exists, a blood flow information cross-sectional image with high reliability can be generated. At the same time, the reliability can be grasped. Furthermore, according to this configuration, when generating three-dimensional blood flow information using a plurality of blood flow information cross-sectional images, it is possible to generate highly reliable three-dimensional blood flow information and grasp the reliability. can do.

(Other embodiments)
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.
This program and a computer-readable storage medium storing the program are included in the present invention.

  Note that the above-described embodiments of the present invention are merely examples of implementation in practicing the present invention, and the technical scope of the present invention should not be construed as being limited thereto. It is. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

801 to 803 B scan image group (optical coherence tomographic image group), 804 to 806 blood flow information cross-sectional image, 807 3D blood flow information

Claims (18)

An imaging apparatus that performs imaging using optical coherence tomography,
An imaging means for repeatedly imaging substantially the same cross section of a measurement target in which a blood vessel exists;
First generation means for generating a plurality of tomographic images in the substantially same cross section based on repeated imaging by the imaging means;
Calculating means for calculating a correlation degree of each tomographic image in the plurality of tomographic images;
Selecting means for selecting a tomographic image having a correlation degree equal to or greater than a predetermined threshold from the plurality of tomographic images;
Using the tomographic image selected by the selection means, a second generation means for generating a blood flow information cross-sectional image in the substantially same cross section;
Imaging means, comprising: a first determination unit that determines a first reliability index that is an index indicating the reliability of the blood flow information slice image based on the tomographic image selected by the selection unit. apparatus. The photographing means repeatedly photographs the substantially identical cross section at a plurality of different positions of the measurement object,
The first generation unit generates the plurality of tomographic images for each of the substantially same cross sections,
The calculation means calculates a correlation degree of each tomographic image in the plurality of tomographic images for each of the substantially same cross section,
The selecting means selects a tomographic image having the correlation degree equal to or greater than a predetermined threshold from the plurality of tomographic images for each of the substantially same cross sections.
The second generation unit generates the blood flow information cross-sectional image using the tomographic image selected by the selection unit for each of the substantially identical cross sections,
The first determination means determines the first reliability index in the blood flow information cross-sectional image based on the tomographic image selected by the selection means for each of the substantially identical cross sections,
Using a plurality of blood flow information cross-sectional images corresponding to a plurality of substantially the same cross section, a third generation means for generating three-dimensional blood flow information in the measurement object;
Using the first reliability index of each blood flow information cross-sectional image in the plurality of blood flow information cross-sectional images, a second reliability index that is an index indicating the reliability of the three-dimensional blood flow information is determined. The imaging apparatus according to claim 1, further comprising: a second determination unit.   The imaging apparatus according to claim 2, further comprising display means for displaying at least one of the first reliability index and the second reliability index.   The three-dimensional blood flow information, the second reliability index, a marker for designating a part of the three-dimensional blood flow information, and the blood flow information relating to a cross section corresponding to the part designated by the marker The imaging apparatus according to claim 2, further comprising display means for displaying the cross-sectional image and the first reliability index in the blood flow information cross-sectional image side by side.   The imaging apparatus according to claim 2, further comprising display means for displaying a warning prompting remeasurement when the second reliability index is equal to or less than a predetermined threshold.   Displaying the 3D blood flow information side by side with the first reliability index in the blood flow information cross-sectional image related to each cross section corresponding to each part of the 3D blood flow information, or the 3D blood The apparatus further comprises display means for displaying the flow information and the first reliability index in the blood flow information cross-sectional image relating to each cross section corresponding to each part of the three-dimensional blood flow information. The imaging device according to claim 2.   7. The first determination unit according to claim 1, wherein the first determination unit determines the first reliability index using the number of tomographic images selected by the selection unit. Shooting device.   The said 1st determination means determines the said 1st reliability parameter | index using the said correlation degree of the tomographic image selected by the said selection means, The any one of Claim 1 thru | or 6 characterized by the above-mentioned. The imaging device described. A layer recognizing unit that performs a process of recognizing a layer for each tomographic image generated by the first generating unit;
The imaging apparatus according to claim 1, wherein the calculation unit calculates the correlation degree based on a layer recognition result by the layer recognition unit.   The said 2nd production | generation means aligns the tomographic image selected by the said selection means, when producing | generating the said blood flow information cross-sectional image, The any one of Claim 1 thru | or 9 characterized by the above-mentioned. The imaging device described. Fourth generation means for generating a front image based on the tomographic image selected by the selection means;
Extracting means for extracting the blood vessel from the front image;
The said 2nd determination means determines the said 2nd reliability parameter | index based on the continuity of the said blood vessel extracted by the said extraction means, The any one of Claim 2 thru | or 6 characterized by the above-mentioned. Shooting device.   The imaging apparatus according to claim 11, wherein the front image is an en-face image or an integrated image obtained by integrating tomographic images selected by the selection unit in a depth direction of the measurement target.   The second determination means determines the second reliability index based on the number of parts where the number of tomographic images selected by the selection means is less than a predetermined number. The imaging device according to any one of 6.   When the number of tomographic images selected by the selection unit is less than a predetermined number, the second generation unit determines whether the number of tomographic images selected by the selection unit is a part close to the corresponding part. The imaging apparatus according to claim 1, wherein a blood flow information cross-sectional image of the corresponding part is generated based on the blood flow information cross-sectional image of a part satisfying a number.   The display apparatus according to claim 2, further comprising a display unit that displays the discontinuous portion of the blood vessel together with the three-dimensional blood flow information or an en-face image generated from the three-dimensional blood flow information. Shooting device. A method for driving an imaging apparatus that performs imaging using optical coherence tomography,
An imaging process of repeatedly imaging substantially the same cross section of a measurement target in which a blood vessel exists,
A first generation step of generating a plurality of tomographic images in substantially the same cross section based on repeated imaging by the imaging step;
A calculation step of calculating a correlation degree of each tomographic image in the plurality of tomographic images;
A selection step of selecting a tomographic image whose correlation degree is a predetermined threshold or more from the plurality of tomographic images;
Using the tomographic image selected in the selection step, a second generation step of generating a blood flow information cross-sectional image in the substantially same cross-section;
And a first determination step of determining a first reliability index that is an index indicating the reliability of the blood flow information cross-sectional image based on the tomographic image selected in the selection step. Device driving method. The photographing step repeatedly photographs the substantially same cross section at a plurality of different positions of the measurement target,
The first generation step generates the plurality of tomographic images for each of the substantially same cross sections,
The calculation step calculates a correlation degree of each tomographic image in the plurality of tomographic images for each of the substantially same cross section,
The selecting step selects a tomographic image having the correlation degree equal to or higher than a predetermined threshold from the plurality of tomographic images for each of the substantially same cross sections,
The second generation step generates the blood flow information cross-sectional image using the tomographic image selected in the selection step for each of the substantially identical cross sections,
The first determination step is to determine the first reliability index in the blood flow information cross-sectional image based on the tomographic image selected in the selection step for each of the substantially identical cross sections,
Using a plurality of blood flow information cross-sectional images corresponding to a plurality of substantially the same cross section, a third generation step of generating three-dimensional blood flow information in the measurement object;
Using the first reliability index of each blood flow information cross-sectional image in the plurality of blood flow information cross-sectional images, a second reliability index that is an index indicating the reliability of the three-dimensional blood flow information is determined. The method according to claim 16, further comprising: a second determination step.   A program for causing a computer to execute each step in the method for driving an imaging device according to claim 16 or 17.