JP6471593B2 - OCT signal processing apparatus and OCT signal processing program - Google Patents

Description

  The present disclosure relates to an OCT signal processing apparatus and an OCT signal processing program for processing an OCT signal acquired by an optical coherence tomography device.

  Divides the light from the light source into measurement light and reference light, acquires the interference light of the measurement light and reference light irradiated to the test object, and processes the acquired interference signal to acquire the tomographic image of the test object An OCT signal processing apparatus is known. In addition, in the OCT signal processing apparatus as described above, there is known an apparatus that acquires a front image of a test object viewed from a direction (front direction) intersecting a cross-sectional direction of the acquired tomographic image.

HC Hendargo, R. Estrada, SJ Chiu, C. Tomasi, S. Farsiu, and J. a. Izatt, “Automated non-rigid registration and mosaicing for robust imaging of distinct retinal capillary beds using speckle variance optical coherence tomography,” Biomed Opt. Express, vol. 4, no. 6, p. 803, May 2013.

  In a conventional OCT signal processing apparatus, when trying to obtain a synthesized front image by joining front images, the image alignment may not be successful.

  In view of the above problems, it is an object of the present disclosure to provide an OCT signal processing apparatus and an OCT signal processing program that can perform more reliable image composition.

  In order to solve the above problems, the present disclosure is characterized by having the following configuration.

(1) OCT data acquisition means for acquiring first OCT data and second OCT data in which at least a part of an acquisition area differs from the first OCT data, and first processing relating to the first OCT data and the second OCT data To generate a first OCT front image based on the first OCT data and a second OCT front image based on the second OCT data, and the first OCT data and the second OCT data are different from the first process. by performing the second processing, the a first 3OCT front image based on the first 1OCT data, image producing means for producing a first 4OCT front image based on the first 2OCT data, the first 1OCT front image and the second 2OCT front a first image position information is relative position information of the image, and the second 3OCT front image Wherein a first 4OCT second image position information is relative position information of the front image, were acquired by the image analysis, on the basis of the acquired first image position information and the second image position information, the Computational control means for computing data position information, which is relative position information between the first OCT data and the second OCT data, is provided.
(2) An OCT signal processing program that is executed in the OCT signal processing device, and is executed by a processor of the OCT signal processing device so that the first OCT data and the first OCT data have a part of an acquisition region. OCT data acquisition step for acquiring at least different second OCT data, and by performing a first process on the first OCT data and the second OCT data, a first OCT front image based on the first OCT data, and the second OCT data And a second OCT front image based on the first OCT data by performing a second process different from the first process on the first OCT data and the second OCT data, Generating a fourth OCT front image based on the second OCT data; An image generating step, the second and the first image position information 1OCT a relative position information of the front image and the second 2OCT front image, relative position information between the first 3OCT front image and the second 4OCT front image The second image position information is obtained by image analysis, and the first OCT data and the second OCT data are relative to each other based on the obtained first image position information and the second image position information. And a calculation control step for calculating data position information, which is accurate position information, is executed by the OCT signal processing apparatus.

1 is a schematic diagram showing a configuration of an OCT signal processing apparatus 1. FIG. 1 is a schematic diagram showing an optical system of an OCT device 10. FIG. 3 is a flowchart showing a control operation of the OCT signal processing apparatus 1. It is a figure explaining acquisition of an OCT signal. It is a figure explaining how to obtain data position information. It is a figure explaining the production | generation method of the synthesized image based on data position information. It is a figure explaining utilization of an analysis result. It is a figure explaining composition of an image when there is no overlap in an acquisition field. It is a figure which shows an example when the distortion of the image image | photographed by the front image is corrected. It is a figure explaining acquisition of a function OCT signal. It is a figure for demonstrating acquisition of motion contrast.

  Hereinafter, embodiments according to the present disclosure will be briefly described with reference to FIGS. The OCT signal processing apparatus of the present embodiment (for example, the OCT signal processing apparatus 1 of FIG. 1), for example, the OCT signal is an optical coherence tomography device (hereinafter abbreviated as an OCT device. For example, the OCT device 10 of FIG. 1). The OCT signal acquired by is processed.

  The OCT signal processing apparatus includes, for example, an OCT data acquisition unit (for example, the control unit 70 in FIG. 1), an image generation unit (for example, the control unit 70), and an arithmetic control unit (for example, the control unit 70). May be.

  For example, the OCT data acquisition unit acquires at least first OCT data and second OCT data. For example, the second OCT data may be different from the first OCT data in at least a part of the acquisition region. The first OCT data and the second OCT data may be, for example, three-dimensional OCT data.

  The OCT data acquisition unit is electrically connected to the OCT device, for example, and may acquire the OCT data directly from the OCT device or indirectly from other media (for example, a computer, a storage medium, etc.). Data may be acquired.

  For example, the image generation unit generates a first OCT image based on the first OCT data and a second OCT front image based on the second OCT data by performing a first process on the first OCT data and the second OCT data. Good. Further, the image generation unit obtains a third OCT front image based on the first OCT data and a fourth OCT front image based on the second OCT data by performing a second process on the first OCT data and the second OCT data, for example. May be. The second process is a process different from the first process, and a front image having a different type from the front image obtained by the first process is generated.

  For example, the calculation control unit may calculate the data position information based on the first image position information and the second image position information. Note that the first image position information may be, for example, relative position information between the first OCT front image and the second OCT front image. The second image position information may be, for example, relative position information between the third OCT front image and the fourth OCT front image. Further, the data position information may be, for example, relative position information between the first OCT data and the second OCT data.

  Note that the image generation unit may perform alignment between a plurality of OCT data based on the data position information and generate a combined front image. For example, the image generation unit includes an OCT front image generated by processing the first OCT data and an OCT front image generated by processing the second OCT data based on the data position information calculated by the calculation control unit. A combined front image may be generated by aligning.

  The first process may be a process for generating the first OCT front image and the second OCT front image based on the first OCT data and the second OCT data in the first depth region, for example. In this case, the second process generates the third OCT front image and the fourth OCT front image based on the first OCT data and the second OCT data in the second depth region having a depth different from the first depth region. It may be a process to do.

  Note that the image generation unit may perform a segmentation process on each of the first OCT data and the second OCT data. Then, the image generation unit may generate an OCT front image for each layer extracted by the segmentation process. Accordingly, the image generation unit generates the first OCT front image and the second OCT front image related to the first layer, and the third OCT front image and the fourth OCT related to the second layer that differ from the first layer in the depth direction. A front image may be generated. Of course, the image generation unit may generate an OCT front image for the entire OCT data.

  At least one of the first OCT data and the second OCT data may be motion contrast data. The motion contrast data is obtained, for example, by processing a plurality of temporally different OCT signals obtained at the same position. As a method for acquiring motion contrast data, for example, a method such as Doppler, Speckle Variance, Correlation Mapping, or the like may be used. For example, blood flow information of the subject can be acquired by the motion contrast data.

  The image generation unit may generate an intensity front image obtained by imaging the signal intensity based on at least one of the first OCT data and the second OCT data. In this case, the image generation unit may generate an intensity front image as the first OCT front image and the second OCT front image, or may generate an intensity front image as the third OCT front image and the second OCT front image.

  The OCT device may be a polarization-sensitive OCT device. In this case, at least one of the first OCT data and the second OCT data may be polarization OCT data acquired by a polarization sensitive OCT device. For example, the polarization-sensitive OCT device may detect the polarization characteristic of the measurement light reflected by the test object.

  The calculation control unit may calculate the data position information based on the acquired position information, the first image position information, and the second image position information. Here, the acquisition position information may be, for example, acquisition position information indicating a position where the first OCT data and the second OCT data are acquired. For example, the arithmetic control unit may acquire the acquisition position information of the first OCT data and the second OCT data.

  Note that the arithmetic control unit may acquire the first analysis information by performing image analysis on the first OCT front image. Further, the arithmetic control unit may acquire the second analysis information by performing image analysis on the second OCT front image. In this case, the arithmetic control unit may acquire the first image position information based on the first analysis information and the second analysis information. The analysis information includes, for example, lesion detection information. For example, the arithmetic control unit may acquire the first image position information based on the position information of the lesion part detected in each of the first OCT front image and the second OCT front image.

  The arithmetic control unit may acquire the first analysis information by performing image analysis on at least one of the 1OCT front image and the third OCT front image. Further, the arithmetic control unit may acquire the second analysis information by performing image analysis on at least one of the second OCT front image and the fourth OCT front image. In this case, the arithmetic control unit may superimpose at least one of the first analysis information and the second analysis information on the combined front image generated by the image generation unit. For example, the arithmetic control unit may display a composite front image on which at least one of the first analysis information and the second analysis information is superimposed on a display unit or the like. Note that the synthesized front image on which at least one of the first analysis information and the second analysis information is superimposed may be any synthesized image, and is not limited to an image synthesized by a specific method.

  Note that the OCT data acquisition unit may acquire second OCT data in which a part of the acquisition region overlaps with the first OCT data. In this case, the arithmetic control unit may acquire the first image position information by detecting the image misalignment in the first overlapping region where the images of the first OCT front image and the second OCT front image overlap. Furthermore, the arithmetic control unit may acquire the second image position information by detecting the image displacement in the second overlapping region where the images of the third OCT front image and the fourth OCT front image overlap.

  In this case, for example, the arithmetic control unit may acquire the first image position information by detecting a positional shift between the first OCT front image and the second OCT front image in the first overlapping region. Further, the arithmetic control unit may acquire the second image position information by detecting a positional shift between the third OCT front image and the fourth OCT front image in the second overlapping region, for example.

  Note that the OCT data acquisition unit may acquire at least second OCT data in which the entire acquisition region is different from the first OCT data. In this case, the arithmetic control unit may acquire the first image position information based on the continuity between the end of the first OCT front image and the end of the second OCT front image. Furthermore, the arithmetic control unit may acquire the second image position information based on continuity between the end of the third OCT front image and the end of the fourth OCT front image.

  Note that the arithmetic control unit may acquire at least one of the first image distortion information and the second image distortion information. Here, the first image distortion information may be information indicating image distortion between the first OCT front image and the second OCT front image, for example. Further, the second image distortion information may be information indicating image distortion between the third OCT front image and the fourth OCT front image, for example.

  Note that the calculation control unit may calculate the data position information by statistical processing using the first image position information and the second image position information. For example, a representative value calculated by statistical processing using the first image position information and the second image position information may be acquired as the data position information. The representative value may be, for example, an average value, a median value, a mode value, or the like. Of course, the same applies when three or more types of OCT front images are generated by the image generation unit and three or more pieces of image position information are acquired. For example, the calculation control unit may acquire a representative value calculated by statistical processing using three or more pieces of image position information as data position information.

  Note that the arithmetic control unit may include, for example, a processor (for example, CPU 71), a storage unit (for example, ROM 72), and the like. In this case, the arithmetic control unit may execute the OCT signal processing program stored in the storage unit by the processor. For example, the OCT signal processing program may include an OCT data acquisition step, an image generation step, and an arithmetic control step.

  For example, the OCT data acquisition step may be a step of acquiring at least second OCT data in which the first OCT data and the first OCT data are at least partially different from each other in an acquisition region.

  For example, the image generation step generates the first OCT front image and the second OCT front image by performing a first process on the first OCT data and the second OCT data, and the first OCT data and the second OCT data. It may be a step of generating a third OCT front image and a fourth OCT front image by performing a second process different from the above process.

  For example, the calculation control step is a step of acquiring the first image position information and the second image position information by image analysis, and calculating the data position information based on the first image position information and the second image position information. There may be.

<Example>
Hereinafter, the OCT signal processing apparatus 1 of a present Example is demonstrated using drawing. The OCT signal processing apparatus 1 illustrated in FIG. 1 processes, for example, an OCT signal acquired by the OCT device 10.

  For example, the OCT signal processing apparatus 1 includes a control unit 70. For example, the control unit 70 is realized by a general CPU (Central Processing Unit) 71, a ROM 72, a RAM 73, and the like. The ROM 72 of the control unit 70 includes an OCT signal processing program for processing the OCT signal, various programs for controlling the operation of the device (for example, the OCT device 10) connected to the OCT signal processing apparatus 1, and initial values. Etc. are stored. The RAM 73 temporarily stores various information. The control unit 70 may be configured by a plurality of control units (that is, a plurality of processors).

  As shown in FIG. 1, for example, a storage unit (for example, a non-volatile memory) 74, an operation unit 76, a display unit 75, and the like are electrically connected to the control unit 70. The storage unit 74 is a non-transitory storage medium that can retain stored contents even when power supply is interrupted. For example, a hard disk drive, a flash ROM, a removable USB memory, or the like can be used as the storage unit 74.

  Various operation instructions by the examiner are input to the operation unit 76. The operation unit 76 outputs a signal corresponding to the input operation instruction to the CPU 71. For the operation unit 76, for example, at least one of user interfaces such as a mouse, a joystick, a keyboard, and a touch panel may be used.

  The display unit 75 may be a display mounted on the apparatus main body or a display connected to the main body. A display of a personal computer (hereinafter referred to as “PC”) may be used. A plurality of displays may be used in combination. The display unit 75 may be a touch panel. When the display unit 75 is a touch panel, the display unit 75 functions as the operation unit 76. The display unit 75 displays, for example, image data obtained by processing the OCT signal acquired by the OCT device 10.

<OCT device>
Hereinafter, an outline of the OCT device 10 will be described. In the present embodiment, for example, an OCT device 10 that irradiates the eye E with measurement light and acquires an OCT signal acquired by the reflected light and the measurement light will be described as an example. For example, the OCT device 10 captures a tomographic image of the eye E by acquiring an OCT signal. The OCT device 10 mainly includes, for example, an OCT optical system 100, a front observation optical system 200, and a fixation target projection unit 300. In this embodiment, the OCT device is connected to the control unit 70 and is controlled by the CPU 71. Of course, the OCT device may include a CPU (not shown) different from the CPU 71 and perform various controls for obtaining the OCT signal.

  The OCT optical system 100 irradiates the eye E with measurement light. The OCT optical system 100 detects the interference state between the measurement light reflected from the eye E and the reference light by the detector 120. The OCT optical system 100 includes, for example, a scanning unit (for example, an optical scanner) 108. For example, the scanning unit 108 changes the scanning position of the measurement light on the eye to be examined in order to change the imaging position on the eye to be examined. The CPU 71 controls the operation of the scanning unit 108 based on the set scanning position information, and acquires an OCT signal based on the light reception signal from the detector 120.

<OCT optical system>
The OCT optical system 100 is a so-called optical coherence tomography (OCT) optical system. The OCT optical system 100 splits the light emitted from the measurement light source 102 into measurement light (sample light) and reference light by a coupler (light splitter) 104. The OCT optical system 100 guides the measurement light to the fundus oculi Ef of the eye E by the measurement optical system 106 and guides the reference light to the reference optical system 110. Thereafter, the detector 120 receives interference light obtained by combining the measurement light reflected by the eye E and the reference light.

  The detector 120 detects an interference state between the measurement light and the reference light. In the case of Fourier domain OCT, the spectral intensity of the interference light is detected by the detector 120, and a depth profile (A scan signal) in a predetermined range is obtained by Fourier transform on the spectral intensity data. Examples include Spectral-domain OCT (SD-OCT) and Swept-source OCT (SS-OCT). Moreover, Time-domain OCT (TD-OCT) may be used.

  In the case of SD-OCT, a low-coherent light source (broadband light source) is used as the light source 102, and the detector 120 is provided with a spectroscopic optical system (spectrum meter) that separates interference light into each frequency component (each wavelength component). . The spectrum meter includes, for example, a diffraction grating and a line sensor.

  In the case of SS-OCT, a wavelength scanning light source (wavelength variable light source) that changes the emission wavelength at a high speed in time is used as the light source 102, and a single light receiving element is provided as the detector 120, for example. The light source 102 includes, for example, a light source, a fiber ring resonator, and a wavelength selection filter. Examples of the wavelength selection filter include a combination of a diffraction grating and a polygon mirror, and a filter using a Fabry-Perot etalon.

  The light emitted from the light source 102 is split into a measurement light beam and a reference light beam by the coupler 104. Then, the measurement light flux passes through the optical fiber and is then emitted into the air. The light beam is condensed on the fundus oculi Ef via the scanning unit 108 and other optical members of the measurement optical system 106. Then, the light reflected by the fundus oculi Ef is returned to the optical fiber through a similar optical path.

  The scanning unit 108 scans the measurement light in the XY direction (transverse direction) on the fundus. The scanning unit 108 is disposed at a position substantially conjugate with the pupil. For example, the scanning unit 108 includes two galvanometer mirrors 51 and 52, and the reflection angle thereof is arbitrarily adjusted by the drive mechanism 50.

  Thereby, the reflection (advance) direction of the light beam emitted from the light source 102 is changed and scanned in an arbitrary direction on the fundus. That is, a “B scan” is performed on the fundus oculi Ef. Note that the scanning unit 108 may be configured to deflect light. For example, in addition to a reflective mirror (galvano mirror, polygon mirror, resonant scanner), an acousto-optic device (AOM) that changes the traveling (deflection) direction of light is used.

  The reference optical system 110 generates reference light that is combined with reflected light acquired by reflection of measurement light at the fundus oculi Ef. The reference optical system 110 may be a Michelson type or a Mach-Zehnder type. The reference optical system 110 is formed by, for example, a reflection optical system (for example, a reference mirror), and reflects light from the coupler 104 back to the coupler 104 by being reflected by the reflection optical system and guides it to the detector 120. As another example, the reference optical system 110 is formed by a transmission optical system (for example, an optical fiber), and guides the light from the coupler 104 to the detector 120 by transmitting the light without returning.

  The reference optical system 110 has a configuration in which the optical path length difference between the measurement light and the reference light is changed by moving an optical member in the reference optical path. For example, the reference mirror is moved in the optical axis direction. The configuration for changing the optical path length difference may be arranged in the measurement optical path of the measurement optical system 106.

<Front observation optical system>
The front observation optical system 200 is provided to obtain a front image of the fundus oculi Ef. The observation optical system 200 includes, for example, an optical scanner that two-dimensionally scans the fundus of measurement light (for example, infrared light) emitted from a light source, and a confocal aperture that is disposed at a position substantially conjugate with the fundus. And a second light receiving element for receiving the fundus reflection light, and has a so-called ophthalmic scanning laser ophthalmoscope (SLO) device configuration.

  Note that the configuration of the observation optical system 200 may be a so-called fundus camera type configuration. The OCT optical system 100 may also serve as the observation optical system 200. That is, the front image may be acquired using data forming a tomographic image obtained two-dimensionally (for example, an integrated image in the depth direction of the three-dimensional tomographic image, at each XY position). The integrated value of the spectrum data.

<Fixation target projection unit>
The fixation target projecting unit 300 includes an optical system for guiding the line-of-sight direction of the eye E. The projection unit 300 has a fixation target presented to the eye E, and can guide the eye E in a plurality of directions.

  For example, the fixation target projection unit 300 has a visible light source that emits visible light, and changes the presentation position of the target two-dimensionally. Thereby, the line-of-sight direction is changed, and as a result, the imaging region is changed. For example, when the fixation target is presented from the same direction as the imaging optical axis, the center of the fundus is set as the imaging site. When the fixation target is presented upward with respect to the imaging optical axis, the upper part of the fundus is set as the imaging region. That is, the imaging region is changed according to the position of the target with respect to the imaging optical axis.

  As the fixation target projection unit 300, for example, a configuration in which the fixation position is adjusted by the lighting positions of LEDs arranged in a matrix, light from a light source is scanned using an optical scanner, and fixation is performed by lighting control of the light source. Various configurations such as a configuration for adjusting the position are conceivable. The projection unit 300 may be an internal fixation lamp type or an external fixation lamp type.

<Control action>
A control operation when processing the OCT signal acquired by the OCT device 10 in the OCT signal processing apparatus as described above will be described based on the flowchart of FIG. The OCT signal processing apparatus 1 of this embodiment processes OCT signals acquired in at least two consecutive different regions. In the following description, a case where the eye E is measured by the OCT device 10 and the acquired OCT signal is processed will be described. The OCT device 10 is not limited to the eye E, and may be another part of the living body or a substance.

<OCT signal acquisition>
First, an OCT signal is detected by the OCT device 10. For example, the CPU 71 controls the fixation target projection unit 300 to project the fixation target onto the subject. Then, the CPU 71 automatically controls the drive unit (not shown) so that the measurement optical axis comes to the center of the pupil of the eye E based on the anterior eye observation image captured by the anterior eye observation camera (not shown). Align.

  When the alignment is completed, the CPU 71 controls the OCT device 10 and measures the eye E to be examined. The CPU 71 scans the eye under measurement with the scanning unit 108 and acquires an OCT signal of the fundus oculi Ef. For example, the CPU 71 scans the measurement light in at least two continuous regions on the fundus oculi Ef, and acquires an OCT signal for each region. For example, as illustrated in FIG. 4A, the OCT device 10 may acquire an OCT signal in a region A1 that is one part of the fundus oculi Ef and a region A2 that is a part different from the region A1. Note that the area A1 and the area A2 may be partially overlapped or may be continuous without overlapping. In addition, the OCT device 10 may acquire OCT signals in a plurality of regions, not limited to two regions.

(Step S1)
First, the CPU 71 controls the OCT device 10, scans the measurement light in the area A1, and acquires the OCT signal of the area A1. For example, the CPU 71 controls driving of the scanning unit 108 and scans the measurement light in the area A1. At this time, for example, the measurement light is scanned in the x direction along the scanning lines SL1, SL2,..., SLn shown in FIG. Note that scanning the measurement light in a direction intersecting the optical axis direction of the measurement light (for example, the x direction) is referred to as “B scan”. The OCT signal obtained by one B scan will be described as one frame OCT signal. The CPU 71 acquires the OCT signal detected by the detector 120 while scanning the measurement light. The CPU 71 acquires information on the OCT signal acquired in the area A1 as OCT data D1, and stores it in the storage unit 74.

(Step S2)
When the acquisition of the OCT signal in the area A1 is completed, the CPU 71 starts acquiring the OCT signal in the area A2. For example, the CPU 71 scans the measurement light in the area A2 and acquires the OCT signal of the area A2 as in the area A1 (see FIG. 4B). Then, the CPU 71 acquires information on the OCT signal acquired in the area A2 as OCT data D2, and stores it in the storage unit 74.

  Note that the CPU 71 may include a functional OCT signal in the OCT signal acquired as OCT data. The functional OCT signal is an OCT signal for acquiring a motion contrast that captures, for example, blood flow, movement of an object, or change. For example, the functional OCT signal may be at least two OCT signals that are temporally different with respect to the same position on the eye to be examined. In the following description, a case where functional OCT signals are acquired in the regions A1 and A2 of the fundus oculi Ef will be described. The details of acquiring the function OCT signal and motion contrast will be described later.

(Step 3)
Next, the CPU 71 generates a plurality of types of front images for the OCT data D1 and D2 acquired by the areas A1 and A2. Here, the front image may be an image when the at least part of the living tissue is viewed from the optical axis direction (for example, the z direction) of the measurement light (so-called “En face image”). An image in a direction perpendicular to the cross-sectional direction may be used.

In the example of FIG. 5, two types of front images generated in different areas in the z direction are generated. That is, based on the OCT data D1, the front image Pn1 in the first depth region and the front image Pn2 in the second depth region are generated as two types of front images. Then, based on the OCT data D2, a front image Pn3 in the first depth region and a front image Pn4 in the second depth region are generated as two types of front images. Of course, the CPU 71 may generate three or more types of front images.
As a method for generating a front image from OCT data, for example, a method of extracting OCT data for at least a partial region in the depth direction can be cited. In this case, for example, the front image may be generated using the luminance value of the OCT data extracted for at least a part of the depth region.

  Here, as a method of separating the region of the fundus oculi Ef in the depth direction, such as the first depth region and the second depth region described above, for example, a tomographic image based on an OCT signal can be used. A method for detecting the boundary of the retinal layer can be mentioned. For example, the CPU 71 may detect the boundary of the retinal layer of the eye E by detecting the edge of the intensity image whose luminance value is determined according to the intensity of the OCT signal. For example, the CPU 71 applies a nerve fiber layer (NFL), a ganglion cell layer (GCL), a retinal pigment epithelium (RPE), or the like based on the intensity image of the eye E to be examined. The retinal layer of the optometry E may be separated.

  Further, since there are many retinal blood vessels at the boundary of the retinal layer, the CPU 71 may separate a region where many blood vessels are distributed based on the detection result of the retinal layer boundary. Of course, the CPU 71 may separate the blood vessel distribution region based on the blood vessel distribution detected from the motion contrast image. For example, the CPU 71 may separate the retina region into a surface layer, an intermediate layer, a deep layer, and the like based on the distribution of blood vessels.

  The CPU 71 may generate a front image in at least one of the separated depth regions. Of course, the front image may be generated by performing a calculation for a plurality of depth regions. In this case, the plurality of depth regions do not have to be adjacent regions, but may be regions that are located apart from each other.

(Step S4)
Next, the CPU 71 detects image position information indicating a relative image position for each front image of the same type. In the above example, the CPU 71 includes the image position information J1 of the front image Pn1 and the front image Pn3 generated in the first depth region, and the front image Pn2 and the front image Pn4 generated in the second depth region. Image position information J2 is detected.
The image position information may be detected by aligning each image. For example, image alignment may be performed using the front image Pn1 as a standard image and the front image Pn3 as a reference image, and pixel shift amounts in the x and y directions of the reference image with respect to the standard image may be detected as image position information. .

<Image alignment method>
Note that image alignment methods include, for example, a phase-only correlation method, a method using various correlation functions, a method using Fourier transform, a method based on feature point matching, an alignment method including affine transformation, and distortion correction (for example, Various image processing techniques such as non-rigid registration, etc.) may be used.

  For example, the CPU 71 may shift the positions of the base image and the reference image one pixel at a time, and perform image alignment so that the two images are the best matched (the correlation is the highest). Then, the CPU 71 may detect a position shift direction and a position shift amount between both images. Further, a common feature point may be extracted from a predetermined standard image and reference image, and a position shift direction and a position shift amount of the extracted feature point may be detected.

  When image conversion such as affine conversion or non-rigid registration is performed, the CPU 71 may acquire a numerical value related to image conversion, a determinant, or the like as image position information.

  Note that, in the alignment of the front image, the position information of the acquisition areas A1 and A2 of the respective OCT data D1 and D2 may be used. For example, alignment may be performed by performing image processing in a state where the positions of the front images are specified to some extent based on the position information of the acquisition areas A1 and A2. In this case, the CPU 71 determines the positions of the acquisition regions A1 and A2 based on information such as the scanning position of the measurement light when the OCT data D1 and D2 are acquired and the fixation position of the fixation target presented to the eye E. You may ask for information. In this way, the processing speed of image alignment may be increased by using the position information of the acquisition areas A1 and A2 of the OCT data D1 and D2.

(Step S5)
When image position information is acquired for each type of image, the CPU 71 acquires data position information J0 indicating relative position information of the OCT data D1 and D2 based on the acquired image position information J1 and J2. . For example, the data position information J0 may be acquired by calculation using the image position information J1 and J2.

  For example, the CPU 71 may acquire the data position information J0 by statistical processing using the image position information J1 and J2. Examples of the statistical processing include calculation of an average value and calculation of a median value. For example, it is assumed that the amount of deviation in the x direction and the amount of deviation in the y direction of an image are indicated by (x, y). For example, when the image position information J1 is (6, 3) and the image position information J2 is (2, 1), the average value of the image position information J1, J2 is calculated. 2).

  Note that, when the CPU 71 acquires three or more pieces of image value information from three or more types of front images acquired from the respective OCT data D1 and D2, the CPU 71 may obtain the median value as the data position information J0. For example, a value located at the center when the image position information is arranged in the order of numerical values may be acquired as the data position information J0. As described above, by using the median value, it is possible to obtain appropriate data position information J0 even when there is an outlier (a value greatly deviating from other values) in the plurality of pieces of image position information.

  As described above, the CPU 71 may remove outliers by performing statistical processing using the image position information J1 and J2. As a result, the CPU 71 may acquire more likely data position information J0.

  Similarly, when three or more types of front images are generated, data position information J0 may be acquired by performing calculation using three or more pieces of image position information acquired from various images.

(Step S6)
The CPU 71 aligns the OCT data D1 and D2 using the data position information J0 acquired in step S5. In this case, the entire OCT data may be aligned. However, the present invention is not limited to this. For example, in the first depth region, the front image generated based on each of the OCT data D1 and D2 may be aligned according to the data position information J0. Furthermore, in the second depth region, the front image generated based on each of the OCT data D1 and D2 may be aligned according to the data position information J0. Of course, the CPU 71 may use the data position information J0 for alignment of the front image generated in the depth region other than the first and second depth regions (see FIG. 6).

  As described above, by acquiring data position information indicating a relative position between OCT data based on a plurality of pieces of image position information obtained from two or more types of front images, the front image is more aligned. Can be done accurately.

  For example, in the front image Pn1 and the front image Pn3 generated in the first depth region, when the first depth region of one image is not well separated, the image processing of the front image Pn1 and the front image Pn3 is performed. The alignment could be affected. However, even if the separation of a certain depth region is not successful by obtaining data position information between OCT data from image position information obtained by aligning a plurality of types of front images, good composition Images can be acquired.

  Furthermore, when aligning a front image of a type that was not used for obtaining the data position information J0 (for example, the composite image Pw3 in FIG. 6), if the data position information J0 is used, the image alignment process is performed. Therefore, the processing speed when compositing images can be increased.

  Note that the CPU 71 may perform image analysis on an image generated based on each of the OCT data D1 and D2 acquired by the OCT device 10. For example, the CPU 71 may detect the lesioned parts B1 and B2 of the eye E by analyzing the image Pn2 based on the OCT data D1 (see FIG. 7). Similarly, the CPU 71 may detect the lesioned part B3 of the eye E by analyzing the image Pn4 based on the OCT data D2. As a method for detecting a lesioned part, for example, a part where blood flow is stagnant or a part where it does not exist may be detected by detecting a region where the luminance of the image is low.

  Then, the CPU 71 may reflect the detected lesioned part in the synthesized image after synthesis. For example, the lesioned part B1 detected in the front image Pn2 may be reflected in the synthesized image Pw2 after synthesis. Thus, the examiner can easily grasp the position of the lesioned part B1 in the composite image Pw2.

  Further, the CPU 71 may use the same lesion portion detected in each of the OCT data D1 and D2 for alignment when synthesizing the front image. For example, in FIG. 7, the CPU 71 causes the front image Pn2 and the front surface Pn2 to overlap with the lesioned part B2 detected from the front image Pn2 based on the OCT data D1 and the lesioned part B3 detected from the front image Pn4 based on the OCT data D2. The image position information J2 of the image Pn4 may be acquired. As described above, the image analysis information may be used when acquiring the image position information of each type of front image. Thus, the CPU 71 can more accurately align each type of front image.

  As shown in FIG. 8A, when there is no overlap between the areas A3 and A4 from which the OCT signals are acquired, the continuity of the front images Pn5 and Pn6 of the OCT data acquired in each area is likely to occur. Alternatively, the image position information of the front image may be acquired. For example, as shown in FIG. 8B, feature regions (for example, blood vessel portions) shown in the front image Pn5 and the front image Pn6 are detected so that the continuity of the feature regions is maintained between the front images. Image position information may be acquired.

  Note that the CPU 71 may correct, for example, distortion of the front image. For example, as shown in FIG. 9, a case where at least one of the front image Pn7 based on the OCT data D1 and the front image Pn8 based on the OCT data D2 is distorted is shown. In this case, feature regions (for example, blood vessel portions) appearing in the front image Pn7 and the front image Pn8 do not match, and alignment is difficult. In such a case, the CPU 71 may combine the front image Pn7 and the front image Pn8 by non-rigid registration. Then, the CPU 71 may acquire the result of non-rigid registration as image position information. Thereby, even when distortion occurs in at least a part of the plurality of OCT data, the alignment between the OCT data can be suitably performed.

<About motion contrast>
Hereinafter, acquisition of motion contrast will be described. For example, the OCT signal processing apparatus 1 according to the present embodiment acquires motion contrast based on the function OCT signal. For example, the CPU 71 may perform a plurality of B scans with a time interval in each scanning line, and obtain a plurality of OCT signals having different times as function OCT signals. For example, as shown in FIG. 10, the CPU 71 performs the second B scan on the same scanning line as the first after a predetermined time has elapsed after performing the first B scan at a certain time. The CPU 71 may acquire a plurality of OCT signals having different times by acquiring the OCT signals detected by the detector 120 at this time.

  For example, FIG. 10 shows a case where a plurality of B scans with different times are performed on the scan lines SL1, SL2,..., SLn. For example, FIG. 10 scans the scan line SL1 at times T11, T12,..., T1N, scans the scan line SL2 at times T21, T22,..., T2N, and scans the scan line SLn at times Tn1, Tn2. ..., TnN. In FIG. 10, the direction of the z axis is the direction of the optical axis of the measurement light. The x-axis direction is perpendicular to the z-axis and is the left-right direction of the subject. The y-axis direction is perpendicular to the z-axis and is the vertical direction of the subject.

  For example, the CPU 71 may acquire a plurality of OCT signals having different times by performing a plurality of B scans having different times in each scanning line in the same manner as the scanning line SL1. Note that the CPU 71 may acquire N frames of OCT signals at different times by repeating scanning at the same position N (natural number of 2 or more) times. In this way, the CPU 71 may acquire OCT signals of two or more frames having different times.

<Calculation of motion contrast>
Next, processing for acquiring motion contrast based on the function OCT signal will be described. The CPU 71 stores a plurality of OCT signals acquired from the OCT device 10 as described above in the storage unit 74. Then, the CPU 71 processes a plurality of OCT signals stored in the storage unit 74 and acquires a complex OCT signal. For example, the CPU 71 performs a Fourier transform on the OCT signal. For example, if the signal at the nth (x, z) position in the N frame is represented by An (x, z), the CPU 71 obtains a complex OCT signal An (x, z) by Fourier transform. The complex OCT signal An (x, z) includes a real component and an imaginary component.

  And CPU71 may process the acquired complex OCT signal and may acquire motion contrast. As a method of processing the complex OCT signal, for example, a method of calculating an intensity difference of the complex OCT signal, a method of calculating a phase difference of the complex OCT signal, a method of calculating a vector difference of the complex OCT signal, a level of the complex OCT signal, and the like. A method of multiplying the phase difference and the vector difference, a method of using signal correlation (correlation mapping), and the like are conceivable. In this embodiment, a method for calculating a phase difference will be described as an example.

  First, the CPU 71 calculates a phase difference with respect to the complex OCT signal A (x, z) acquired at least at two different times at the same position. The CPU 71 calculates the change in phase using, for example, the following equation (1). In this embodiment, for example, when different times are measured N times, T1 and T2, T2 and T3,..., T (N-1) and TN are calculated (N-1) times. (N-1) pieces of data are calculated (see, for example, FIG. 3). Of course, the combination of time is not limited to the above, and the combination may be changed as long as the time is different. Note that An in the equation indicates a signal acquired at time TN, and * indicates a complex conjugate.

  As described above, the CPU 71 acquires the phase difference profile in the depth direction (A scan direction) related to the phase difference of the complex OCT signal. For example, the CPU 71 may acquire a luminance profile whose luminance is determined according to the size of the phase difference profile, and may acquire a motion contrast image in which the luminance profiles are arranged in the B-scan direction. In this case, the CPU 71 causes the storage unit 74 to store motion contrast image data acquired based on the phase differences of a plurality of complex OCT signals at the same position at different times.

  In the above embodiment, the OCT signal processing apparatus 1 has acquired the functional OCT signal as OCT data and generates a front image based on the motion contrast of the eye to be examined. However, the present invention is not limited to this. For example, the OCT signal processing apparatus 1 may generate a front image based on the intensity of a single OCT signal acquired by one B scan in each scan line. In this case, the type of the front image for acquiring the image position information may include a front image based on intensity. That is, the CPU 71 may acquire image position information of the intensity front image based on the OCT data D1 and the intensity front image based on the OCT data D2.

10 OCT device 70 Control unit 71 CPU
72 ROM
73 RAM
74 Memory 75 Monitor 76 Operation Unit 100 OCT Optical System 108 Scanning Unit 200 Front Observation Optical System 300 Fixation Target Projection Unit

Claims (5)

OCT data acquisition means for acquiring first OCT data and second OCT data in which at least a part of an acquisition area differs from the first OCT data;
By performing a first process on the first OCT data and the second OCT data, a first OCT front image based on the first OCT data and a second OCT front image based on the second OCT data are generated,
By performing a second process different from the first process on the first OCT data and the second OCT data, a third OCT front image based on the first OCT data, a fourth OCT front image based on the second OCT data, and Image generating means for generating
Wherein the first image position information first 1OCT a relative position information of the front image and the second 2OCT front image, the second image is the relative position information between the first 4OCT front image and the second 3OCT front image Position information is acquired by image analysis, and based on the acquired first image position information and second image position information, relative position information between the first OCT data and the second OCT data. An OCT signal processing apparatus comprising: an arithmetic control unit that calculates data position information.   The image generation means is an OCT front image generated by processing the first OCT data and an OCT generated by processing the second OCT data based on the data position information calculated by the calculation control means. The OCT signal processing apparatus according to claim 1, wherein a combined front image is generated by combining a plurality of OCT front images by aligning the front images. The first process is a process of generating the first OCT front image and the second OCT front image based on the first OCT data and the second OCT data in a first depth region,
The second process generates the third OCT front image and the fourth OCT front image based on the first OCT data and the second OCT data in a second depth region different from the first depth region. The OCT signal processing apparatus according to claim 1 or 2, wherein It said image generation means, the first 1OCT respectively performs segmentation processing on the data and the second 2OCT data, by generating an OCT front image for each layer extracted by the segmentation process, the related first layer first 1OCT front image and to generate a said first 2OCT front image, claims, characterized in that to generate a different second of the first 4OCT front image and the second 3OCT front image for layer with respect to said first depth and layers The OCT signal processing apparatus according to any one of 1 to 3. An OCT signal processing program executed in the OCT signal processing device, and executed by the processor of the OCT signal processing device,
OCT data acquisition step of acquiring first OCT data and second OCT data in which at least a part of an acquisition area differs from the first OCT data;
By performing a first process on the first OCT data and the second OCT data, a first OCT front image based on the first OCT data and a second OCT front image based on the second OCT data are generated,
By performing a second process different from the first process on the first OCT data and the second OCT data, a third OCT front image based on the first OCT data, a fourth OCT front image based on the second OCT data, and An image generation step for generating
First image position information, which is relative position information between the first OCT front image and the second OCT front image, and a second image, which is relative position information between the third OCT front image and the fourth OCT front image. Position information is acquired by image analysis, and based on the acquired first image position information and second image position information, relative position information between the first OCT data and the second OCT data. An OCT signal processing program that causes the OCT signal processing device to execute a calculation control step for calculating data position information.

Images