JP2017202369A - Ophthalmologic image processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate a setting for an object region in blood flow measurement, and shorten the time for the setting.SOLUTION: An ophthalmologic image processing device according to an embodiment comprises a data processing unit. The data processing unit processes an image acquired from a subject eye by using an optical coherence tomography (OCT) optical system. On the basis of an image including an image region corresponding to the blood vessel of the subject eye, the data processing unit generates information indicating whether the blood vessel is an arteria or a vein.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an ophthalmic image processing apparatus.

  Optical coherence tomography (OCT) is used not only for measuring the form of an object but also for measuring its function. For example, an apparatus for measuring blood flow of a living body using OCT is known. Blood flow measurement using OCT is applied to fundus blood vessels and the like.

JP2013-184018A JP 2009-165710 A Special table 2010-523286

  It is desirable for blood flow measurement to target a region where a pulse wave can be clearly obtained. Typically, it is desirable that the blood vessel to be measured is an artery located in a direction in which a suitable Doppler signal can be obtained. The search for arteries is currently performed by the following method. In the first method, a user designates a cross section that crosses a desired blood vessel, performs blood flow measurement of the blood vessel, analyzes the obtained data, and determines whether the blood vessel is an artery. In this method, a series of processes such as blood vessel selection, cross-section designation, blood flow measurement, and data analysis must be repeated until an appropriate artery is found, which takes time and effort.

  In the second method, live OCT is used. Live OCT is an imaging method in which a section of a living body is repeatedly scanned at a predetermined repetition rate, and a moving image based on data obtained thereby is displayed in real time. In this method, a morphological image and a phase image of a cross section crossing a desired blood vessel are displayed as a moving image. In the phase image, the arteries are represented as areas where the light and dark changes periodically and relatively large, and the veins are represented as areas where the light and dark changes are relatively small. The user determines whether the blood vessel is an artery or a vein by observing the phase image. This determination relies on the user's experience and is inferior in accuracy and reproducibility. Furthermore, a series of processes such as selection of a blood vessel, designation of a cross section, measurement of blood flow, and determination by observation must be repeated until an appropriate artery is found.

  In particular, when blood flow measurement of the fundus is performed, since it is common to use an infrared observation image with poor visibility, it is not easy to select blood vessels.

  One of the objects of the present invention is to facilitate the setting of a target site for blood flow measurement and to shorten the time.

  The embodiment is an ophthalmic image processing apparatus including a data processing unit that processes an image acquired from an eye to be examined using an optical coherence tomography (OCT) optical system, and the data processing unit corresponds to a blood vessel of the eye to be examined. Information indicating whether a blood vessel is an artery or a vein is generated based on an image including an image region to be processed.

  According to the embodiment, it is possible to facilitate the setting of the target site for blood flow measurement and to shorten the time.

It is a schematic diagram showing an example of composition of a blood flow measuring device concerning an embodiment. It is a schematic diagram showing an example of composition of a blood flow measuring device concerning an embodiment. It is a schematic diagram showing an example of composition of a blood flow measuring device concerning an embodiment. It is a schematic diagram showing an example of composition of a blood flow measuring device concerning an embodiment. It is the schematic for demonstrating an example of operation | movement of the blood-flow measuring device which concerns on embodiment. It is the schematic for demonstrating an example of operation | movement of the blood-flow measuring device which concerns on embodiment. It is the schematic for demonstrating an example of operation | movement of the blood-flow measuring device which concerns on embodiment. It is the schematic for demonstrating an example of operation | movement of the blood-flow measuring device which concerns on embodiment. It is a flowchart showing an example of operation | movement of the blood-flow measuring device which concerns on embodiment. It is a schematic diagram showing an example of composition of a blood flow measuring device concerning an embodiment. It is the schematic for demonstrating an example of operation | movement of the blood-flow measuring device which concerns on embodiment. It is a schematic diagram showing an example of composition of a blood flow measuring device concerning an embodiment.

  A blood flow measurement device according to an embodiment will be described in detail with reference to the drawings. The blood flow measurement device according to the embodiment forms a tomographic image or a three-dimensional image of a living body using OCT. The contents of the cited references described in this specification can be incorporated into the embodiments.

  In the following embodiments, a blood flow measurement device capable of measuring the fundus of a living eye using Fourier domain OCT (particularly, spectral domain OCT) will be described. The type of OCT is not limited to the spectral domain, and may be, for example, swept source OCT. The blood flow measurement device according to the embodiment is a device in which an OCT device and a fundus camera are combined, but a fundus imaging device other than the fundus camera and an OCT device may be combined. Examples of such a fundus imaging apparatus include SLO (Scanning Laser Ophthalmoscope), a slit lamp, and a microscope for ophthalmic surgery. In general, the blood flow measuring device of the embodiment is sufficient if it has an OCT function.

<First Embodiment>
[Constitution]
As shown in FIG. 1, the blood flow measurement device 1 includes a fundus camera unit 2, an OCT unit 100, and an arithmetic control unit 200. The fundus camera unit 2 includes an optical system for photographing the fundus and acquiring a front image. This optical system is almost the same as that of a conventional fundus camera. The OCT unit 100 includes an optical system for acquiring data by performing OCT of the fundus. The arithmetic control unit 200 includes a computer that executes various calculations and controls.

(Fundus camera unit 2)
The fundus camera unit 2 shown in FIG. 1 is provided with an optical system for obtaining a two-dimensional image (fundus image) representing the surface form of the fundus oculi Ef of the eye E to be examined. There are observation images and photographed images as fundus images. The observation image is, for example, a monochrome moving image formed at a predetermined frame rate using near infrared light. The captured image is, for example, a color image obtained by flashing visible light, or a monochrome still image using near infrared light or visible light as illumination light. The fundus camera unit 2 may be able to acquire images other than these, such as a fluorescein fluorescent image, an indocyanine green fluorescent image, a spontaneous fluorescent image, and the like.

  The retinal camera unit 2 is provided with a chin rest and a forehead support for supporting the subject's face. Further, the fundus camera unit 2 is provided with an illumination optical system 10 and a photographing optical system 30. The illumination optical system 10 irradiates the fundus oculi Ef with illumination light. The photographing optical system 30 guides the fundus reflection light of the illumination light to an imaging device (CCD image sensor (sometimes simply referred to as a CCD) 35, 38). The imaging optical system 30 guides the measurement light from the OCT unit 100 to the fundus oculi Ef and guides the return light of the measurement light from the fundus oculi Ef to the OCT unit 100.

  The observation light source 11 of the illumination optical system 10 includes, for example, a halogen lamp or an LED (Light Emitting Diode). The light (observation illumination light) output from the observation light source 11 is reflected by the reflection mirror 12 having a curved reflection surface, passes through the condensing lens 13, passes through the visible cut filter 14, and is converted into near infrared light. Become. Further, the observation illumination light is once converged in the vicinity of the photographing light source 15, reflected by the mirror 16, and passes through the relay lenses 17 and 18, the diaphragm 19 and the relay lens 20. Then, the observation illumination light is reflected at the peripheral portion (region around the hole portion) of the aperture mirror 21, passes through the dichroic mirror 46, and is refracted by the objective lens 22 to illuminate the fundus oculi Ef.

  The fundus reflection light of the observation illumination light is refracted by the objective lens 22, passes through the dichroic mirror 46, passes through the hole formed in the central region of the perforated mirror 21, passes through the dichroic mirror 55, and is a focusing lens. 31, reflected by the mirror 32, transmitted through the half mirror 40, reflected by the dichroic mirror 33, and imaged on the light receiving surface of the CCD image sensor 35 by the condenser lens 34. The CCD image sensor 35 detects fundus reflected light at a predetermined frame rate. On the display device 3, an image (observation image) based on fundus reflection light detected by the CCD image sensor 35 is displayed. When the photographing optical system 30 is focused on the anterior segment, an observation image of the anterior segment of the eye E is displayed.

  The imaging light source 15 includes, for example, a xenon lamp or an LED. The light (imaging illumination light) output from the imaging light source 15 is applied to the fundus oculi Ef through the same path as the observation illumination light. The fundus reflection light of the imaging illumination light is guided to the dichroic mirror 33 through the same path as that of the observation illumination light, passes through the dichroic mirror 33, is reflected by the mirror 36, and is reflected by the condenser lens 37 of the CCD image sensor 38. An image is formed on the light receiving surface. On the display device 3, an image (captured image) based on fundus reflection light detected by the CCD image sensor 38 is displayed.

  An LCD (Liquid Crystal Display) 39 displays a fixation target and an eyesight measurement index. The fixation target is an index for fixing the eye E to be examined, and is used at the time of fundus photographing or OCT. By changing the display position of the fixation target on the screen of the LCD 39, the fixation position of the eye E can be changed.

  A part of the light output from the LCD 39 is reflected by the half mirror 40, reflected by the mirror 32, passes through the focusing lens 31 and the dichroic mirror 55, passes through the hole of the perforated mirror 21, and is dichroic. The light passes through the mirror 46, is refracted by the objective lens 22, and is projected onto the fundus oculi Ef.

  Further, the fundus camera unit 2 is provided with an alignment optical system 50 and a focus optical system 60 as in a conventional fundus camera. The alignment optical system 50 generates an index (alignment index) for performing alignment (alignment) of the apparatus optical system with respect to the eye E. The focus optical system 60 generates an index (split index) for focusing on the fundus oculi Ef.

  The light (alignment light) output from the LED 51 of the alignment optical system 50 is reflected by the dichroic mirror 55 via the apertures 52 and 53 and the relay lens 54, passes through the hole of the aperture mirror 21, and reaches the dichroic mirror 46. And is projected onto the eye E by the objective lens 22.

  The return light of the alignment light is detected by the CCD image sensor 35. The light reception image (alignment index image) by the CCD image sensor 35 is displayed together with the observation image. The user can perform the alignment while referring to the alignment index image, similarly to the conventional fundus camera. The arithmetic control unit 200 can also perform alignment by analyzing the position of the alignment index image and moving the optical system (auto alignment function).

  When performing the focus adjustment, the reflecting surface of the reflecting rod 67 is obliquely provided on the optical path of the illumination optical system 10. The light (focus light) output from the LED 61 of the focus optical system 60 passes through the relay lens 62, is separated into two light beams by the split indicator plate 63, passes through the two-hole aperture 64, and is reflected by the mirror 65, The light is focused on the reflecting surface of the reflecting bar 67 by the condenser lens 66 and reflected. Further, the focus light passes through the relay lens 20, is reflected by the perforated mirror 21, passes through the dichroic mirror 46, is refracted by the objective lens 22, and is projected onto the fundus oculi Ef.

  The return light of the focus light is detected by the CCD image sensor 35. The light reception image (split index image) by the CCD image sensor 35 is displayed together with the observation image and the alignment index image. The arithmetic control unit 200 can perform focusing by analyzing the position of the split index and moving the focusing lens 31 and the focus optical system 60 in the same manner as in the past (autofocus function). Further, manual focusing may be performed while referring to the position of the split index image.

  The dichroic mirror 46 synthesizes the optical path of the measurement light for OCT (measurement optical path, measurement arm) with the optical path for fundus imaging. That is, the fundus photographing optical path and the measurement optical path are coaxially formed by the dichroic mirror 46 and share the optical path on the eye E side with respect to the dichroic mirror 46. The dichroic mirror 46 reflects light in a wavelength band used for OCT and transmits light for fundus photographing. In the measurement optical path, a collimator lens unit 40, an optical path length changing unit 41, an optical scanner 42, a focusing lens 43, a mirror 44, and a relay lens 45 are provided in this order from the OCT unit 100 side.

  The optical path length changing unit 41 is movable in the direction of the arrow shown in FIG. 1 and changes the length of the measurement optical path. This change in the optical path length is used for correcting the optical path length according to the axial length of the eye E or adjusting the interference state. The optical path length changing unit 41 includes, for example, a corner cube and a mechanism for moving the corner cube.

  The optical scanner 42 changes the traveling direction of the measurement light LS that passes through the measurement optical path. Thereby, the fundus oculi Ef can be scanned with the measurement light LS. The optical scanner 42 includes, for example, a galvanometer mirror that scans the measurement light LS in the x direction and a galvanometer mirror that scans in the y direction, and is configured to be able to deflect the measurement light LS in an arbitrary direction on the xy plane.

(OCT unit 100)
A configuration example of the OCT unit 100 will be described with reference to FIG. The optical system provided in the OCT unit 100 divides the low-coherence light into reference light and measurement light, and returns the return light and reference light path of the measurement light from the eye E as in the conventional spectral domain type OCT apparatus. The interference light is generated by causing interference with the reference light that has passed through, and the spectral component of the interference light is detected. This detection result (detection signal) is sent to the arithmetic control unit 200.

  When a swept source type OCT apparatus is applied, a wavelength swept light source is provided instead of a low coherence light source, and a balanced photodiode or the like is provided instead of a device (spectrometer) for detecting a spectral component. In general, the OCT unit 100 may have a known configuration corresponding to the type of OCT.

  The light source unit 101 outputs low coherence light L0 (broadband light). The low coherence light L0 includes, for example, a near-infrared wavelength band (approximately 800 nm to 900 nm) and has a temporal coherence length of approximately several tens of micrometers. Alternatively, near infrared light having a center wavelength of 1040 to 1060 nm may be used as the low coherence light L0.

  The light source unit 101 includes a light output device such as a super luminescent diode (SLD), an LED, or an SOA (Semiconductor Optical Amplifier).

  The low coherence light L0 output from the light source unit 101 is guided to the fiber coupler 103 by the optical fiber 102 and is divided into the measurement light LS and the reference light LR.

  The reference light LR is guided by the optical fiber 104 and reaches the optical attenuator (attenuator) 105. The optical attenuator 105 changes the amount of the reference light LR guided to the optical fiber 104 under the control of the arithmetic control unit 200 or by manual operation. The reference light LR whose light amount has been adjusted by the optical attenuator 105 is guided by the optical fiber 104 and reaches the polarization adjuster (polarization controller) 106. The polarization adjuster 106 changes the polarization state of the reference light LR guided through the optical fiber 104. The reference light LR whose polarization state is adjusted by the polarization adjuster 106 reaches the fiber coupler 109.

  The measurement light LS generated by the fiber coupler 103 is guided by the optical fiber 107 and converted into a parallel light beam by the collimator lens unit 105. Further, the measurement light LS reaches the dichroic mirror 46 via the optical path length changing unit 41, the optical scanner 42, the focusing lens 43, the mirror 44, and the relay lens 45. Then, the measurement light LS is reflected by the dichroic mirror 46, is refracted by the objective lens 11, and enters the eye E to be examined. The measurement light LS is reflected and scattered at various depth positions of the fundus oculi Ef. The return light (backscattered light, reflected light, fluorescence, etc.) of the measurement light LS from the fundus oculi Ef travels in the same direction as the forward path in the reverse direction and is guided to the fiber coupler 103, and passes through the optical fiber 108 to the fiber coupler. 109 is reached.

  The fiber coupler 109 causes the return light of the measurement light LS and the reference light LR to interfere with each other. Thereby, the interference light LC is generated. The interference light LC is guided by the optical fiber 110 and is emitted from the emission end 111. Further, the interference light LC is converted into a parallel light beam by the collimator lens 112, spectrally resolved by the diffraction grating 113, condensed by the condenser lens 114, and projected onto the light receiving surface of the CCD image sensor 115. Note that the diffraction grating 118 shown in FIG. 2 is a transmission type, but other types of spectroscopic elements such as a reflection type diffraction grating can also be used.

  The CCD image sensor 115 is a line sensor, for example, and detects each spectral component of the interference light LC and converts it into electric charges. The CCD image sensor 115 accumulates this electric charge, generates a detection signal, and sends it to the arithmetic control unit 200. Instead of the CCD image sensor, another image sensor, for example, a CMOS (Complementary Metal Oxide Semiconductor) image sensor may be used.

(Calculation control unit 200)
The arithmetic control unit 200 analyzes the detection signal input from the CCD image sensor 115 and forms an OCT image. The arithmetic processing for that is the same as the conventional spectral domain OCT.

  The arithmetic control unit 200 controls the fundus camera unit 2, the display device 3, and the OCT unit 100. The fundus camera unit 2 is controlled by controlling the operation of the observation light source 11, the imaging light source 15, the LCD 39, the optical scanner 42, and the LEDs 51 and 61, the focusing lenses 31 and 43, the optical path length changing unit 41, and the focus optical system. 60, as well as the movement control of each of the reflecting bars 67. Control of the OCT unit 100 includes operation control of the light source unit 101, the optical attenuator 105, the polarization adjuster 106, and the CCD image sensor 120.

  The arithmetic control unit 200 includes a processor, a RAM, a ROM, a hard disk drive, a communication interface, and the like. The arithmetic control unit 200 may include an operation device (input device) such as a keyboard and a mouse, and a display device such as an LCD. In this specification, the “processor” is, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), or a programmable logic device (eg, SPLD (Simple LD). It means a circuit such as (Complex Programmable Logic Device) or FPGA (Field Programmable Gate Array). The arithmetic control unit 200 implements the functions according to the embodiment by reading and executing a program stored in a storage circuit or a storage device, for example.

[Control system]
A configuration example of the control system of the blood flow measuring device 1 is shown in FIGS.

(Control unit 210)
The control unit 210 includes, for example, a processor, a RAM, a ROM, a hard disk drive, a communication interface, and the like. The control unit 210 is provided with a main control unit 211 and a storage unit 212. The storage unit 212 stores various data and computer programs.

  The main control unit 211 performs various controls. For example, as shown in FIG. 3, the main control unit 211 controls the CCDs 35 and 38, the focusing drive unit 31A, the optical path length changing unit 41, the optical scanner 42, and the focusing driving unit 43A of the fundus camera unit 2. . Further, the main control unit 211 controls the light source unit 101, the optical attenuator 105, the polarization adjuster 106, and the CCD 115 of the OCT unit 100.

  The focusing drive unit 31A moves the focusing lens 31 in the optical axis direction. Thereby, the focus position of the photographic optical system 30 changes. The focusing drive unit 43A moves the focusing lens 43 in the optical axis direction. As a result, the focus position of the measurement light LS (OCCT measurement focus position) changes. The main control unit 211 can move an optical system provided in the fundus camera unit 2 three-dimensionally by controlling an optical system driving unit (not shown). This movement control of the optical system is used in alignment and tracking. The tracking is a process of moving the apparatus optical system in accordance with the eye movement of the eye E. Prior to tracking, alignment and focus adjustment are performed. Tracking is a function that maintains the state of alignment and focus by causing the position of the apparatus optical system to follow the eye movement.

(Image forming unit 220)
The image forming unit 220 forms tomographic image data and phase image data of the fundus oculi Ef based on the detection signal from the CCD image sensor 115. The image forming unit 220 includes a processor. In this specification, “image data” and “image” based thereon may be identified. The image forming unit 220 includes a tomographic image forming unit 221 and a phase image forming unit 222.

  In the present embodiment, scanning (preliminary measurement) for setting a target region for blood flow measurement and scanning (blood flow measurement) for acquiring blood flow information regarding the region set from the result of the preliminary measurement are executed. Is done.

  In the preliminary measurement, a plurality of cross sections of the fundus oculi Ef are repeatedly scanned with the measurement light LS. The scanning of a plurality of cross sections is, for example, a raster scan along a plurality of scanning lines parallel to each other. The number of scanning lines of the raster scan is, for example, 128, thereby scanning the three-dimensional region of the fundus oculi Ef (three-dimensional scan). Note that the number of scanning patterns and scanning lines is not limited to this example.

  In blood flow measurement, two types of scanning (first scanning and second scanning) are executed based on the region of the fundus oculi Ef set from the result of preliminary measurement. A part set from the result of the preliminary measurement is called a target part. The attention site includes the attention blood vessel and the attention cross section. The target blood vessel is a blood vessel of the fundus oculi Ef set from the result of preliminary measurement. The target blood vessel may be a blood vessel in which a pulse wave is clearly observed, for example, an artery. The cross section of interest is a cross section that intersects the blood vessel of interest. Furthermore, the site of interest may include one or more cross sections located in the vicinity of the target cross section. The one or more cross sections are subjected to an OCT scan for obtaining the inclination of the target blood vessel.

  In the first scan, two or more cross sections intersecting the target blood vessel are scanned with the measurement light LS. Data acquired by the first scan is used to obtain the inclination (orientation) of the blood vessel of interest in the cross section of interest. On the other hand, in the second scan, the cross section of interest that intersects the blood vessel of interest is repeatedly scanned with the measurement light LS. The cross section in which the first scan is performed is arranged in the vicinity of the target cross section. The second scan is Doppler measurement using OCT.

  The target cross sections of the first scan and the second scan are preferably oriented so as to be orthogonal to the traveling direction of the blood vessel of interest on the xy plane. As shown in the fundus oculi image D of FIG. 5, in the present embodiment, for example, in the vicinity of the optic disc Da, there are two cross sections C11 and C12 in which the first scan is performed and an attention cross section C2 in which the second scan is performed. It is set so as to intersect the target blood vessel Db. One of the two cross sections C11 and C12 is positioned upstream of the target blood vessel Db with respect to the target cross section C2, and the other is positioned downstream. The distance between the cross sections C11 and C12 (distance between cross sections) with respect to the target cross section C2 is determined in advance.

  The second scan is preferably performed over at least one cardiac cycle of the patient's heart. Thereby, blood flow information in all time phases of the heart is obtained. The execution time of the second scan may be a predetermined time (for example, 2 seconds) set in advance, or may be a time set for each patient or for each examination. In the latter example, patient heart rate data obtained using an electrocardiograph can be utilized.

(Tomographic image forming unit 221)
The tomographic image forming unit 221 forms a tomographic image based on data obtained by OCT scanning the fundus oculi Ef. The tomographic image forming unit 221 can form a tomographic image based on the data acquired in the preliminary measurement. The tomographic image forming unit 221 can form a tomographic image based on data acquired by blood flow measurement (first scanning and / or second scanning). For example, the tomographic image forming unit 221 includes a tomographic image representing the form of the cross section C11, a tomographic image representing the form of the cross section C12, based on the detection result of the interference light LC obtained by the first scanning with respect to the cross sections C11 and C12. Form. At this time, the cross section C11 can be scanned once to form one tomographic image, and the cross section C12 can be scanned once to form one tomographic image. Alternatively, one tomographic image is acquired based on a plurality of tomographic images obtained by scanning the section C11 a plurality of times, and one sheet is obtained based on a plurality of tomographic images obtained by scanning the section C12 a plurality of times. A tomographic image can be acquired. As an example of processing for acquiring one tomographic image from a plurality of tomographic images, there are processing for improving the image quality by averaging a plurality of tomographic images and processing for selecting an optimal one from a plurality of tomographic images.

  In addition, the tomographic image forming unit 221 forms a tomographic image group representing a time-series change of the form of the cross section of interest C2 based on the detection result of the interference light LC obtained by the second scan with respect to the cross section of interest C2. This process will be described in more detail. In the second scan, the target section C2 is repeatedly scanned as described above. Detection signals are sequentially input from the CCD 115 of the OCT unit 100 to the tomographic image forming unit 221 in accordance with the second scan. The tomographic image forming unit 221 forms one tomographic image of the cross section of interest C2 based on a detection signal group corresponding to one scan of the cross section of interest C2. The tomographic image forming unit 221 forms a series of tomographic images along a time series by repeating this process as many times as the second scanning is repeated. Here, these tomographic images may be divided into a plurality of groups, and the tomographic images of each group may be averaged to improve the image quality.

  The processing executed by the tomographic image forming unit 221 includes noise removal (noise reduction), filter processing, FFT (Fast Fourier Transform), and the like, as in the conventional spectral domain OCT. When another type of OCT is applied, the tomographic image forming unit 221 executes a known process according to the type.

(Phase image forming unit 222)
The phase image forming unit 222 forms a phase image based on data obtained by repeatedly OCT scanning a predetermined part of the fundus oculi Ef. The phase image forming unit 222 forms a phase image representing a time-series change of the phase difference in the scanned cross section based on the data acquired in the preliminary measurement. In the preliminary measurement, a plurality of cross sections of the fundus oculi Ef are repeatedly scanned. The phase image forming unit 222 forms a phase image in each of these cross sections based on the data acquired by the preliminary measurement.

  Further, the phase image forming unit 222 forms a phase image based on data acquired by the second scan of blood flow measurement. For example, the phase image forming unit 222 forms a phase image representing a time-series change of the phase difference in the target cross section C2 based on the detection result of the interference light LS obtained by the second scanning with respect to the target cross section C2.

  The data used for forming the phase image may be the same as the data used by the tomographic image forming unit 221 to form the tomographic image. In this case, the tomographic image and the phase image of the scanned cross section can be easily aligned. That is, for the tomographic image and the phase image formed based on the same data, it is possible to naturally associate the tomographic image pixel and the phase image pixel.

  An example of a phase image forming method will be described. The phase image of this example is obtained by calculating the phase difference between adjacent A-line complex signals (signals corresponding to adjacent scanning points). In other words, the phase image of this example is formed based on the time series change of the pixel value (luminance value) of each pixel of the scanned cross-sectional tomographic image. For an arbitrary pixel, the phase image forming unit 222 considers a graph of a time-series change in luminance value. The phase image forming unit 222 obtains a phase difference Δφ between two time points t1 and t2 (t2 = t1 + Δt) separated by a predetermined time interval Δt in this graph. The phase difference Δφ is defined as the phase difference Δφ (t1) at the time point t1 (more generally, any time point between the two time points t1 and t2). By executing this process for each of a number of preset time points, a time-series change in phase difference at the pixel can be obtained.

  The phase image represents the value of the phase difference at each time point of each pixel as an image. This imaging process can be realized, for example, by expressing the value of the phase difference with the display color or brightness. At this time, a color indicating that the phase has increased along the time series (for example, red) can be different from a color indicating that the phase has decreased (for example, blue). Also, the magnitude of the phase change amount can be expressed by the darkness of the display color. By adopting such an expression method, the direction and size of the blood flow can be presented in color and density. A phase image is formed by executing the above processing for each pixel.

  The time-series change of the phase difference is obtained by ensuring the phase correlation by sufficiently reducing the time interval Δt. At this time, oversampling in which the time interval Δt is set to a value less than the time corresponding to the resolution of the tomographic image in the scanning of the measurement light LS is executed.

(Data processing unit 230)
The data processing unit 230 includes a processor that executes various types of data processing. For example, the data processing unit 230 performs image processing and analysis processing on the image formed by the image forming unit 220. Specific examples thereof include various correction processes such as luminance correction and dispersion correction. Further, the data processing unit 230 performs image processing and analysis processing on an image (fundus image, anterior eye image, etc.) obtained by the fundus camera unit 2. The data processing unit 230 includes a preliminary measurement processing unit 231 and a blood flow measurement processing unit 232.

(Preliminary measurement processing unit 231)
The preliminary measurement processing unit 231 executes processing of data acquired by preliminary measurement for setting a region where blood flow measurement is performed. In this example, the preliminary measurement processing unit 231 generates information (measurement site information) for setting a target site for blood flow measurement based on a phase image formed from data by preliminary measurement. The preliminary measurement processing unit 231 includes a profile generation unit 2311, an arterial region specifying unit 2312, and an information generation unit 2313.

(Profile generation unit 2311)
The profile generation unit 2311 integrates (integrates) each frame of the phase image formed based on the preliminary measurement in the z direction. That is, the profile generation unit 2311 integrates the pixel values of the frame of the phase image in the A line direction (axis direction). Thereby, a plurality of integrated value profiles (time-dependent integrated value profiles) arranged in time series are obtained for each cross section for which preliminary measurement has been performed. Note that the integration of pixel values includes a process of adding values (luminance values representing reflection intensity) of a plurality of pixels arranged along the A line, and may include an operation of processing the obtained integrated value. An example of this processing operation is scale conversion (gradation range conversion).

A specific example of processing executed by the profile generation unit 2311 will be described. Please refer to FIG. 6A and FIG. 6B. FIG. 6A represents the frame F of the phase image for the cross-section for which the preliminary measurement has been performed. In the frame F, an image region (blood vessel region) Fa corresponding to a cross section of the blood vessel is expressed. The blood vessel region Fa represents a cross section of the artery. The frame F is composed of a plurality of A-scan images A _k (k = 1, 2, 3,..., K: for example, K = 512). Each A scan image _Ak is a one-dimensional luminance image along the z direction (A line direction). The plurality of A scan images A _{1 to} A _K are arranged along an arbitrary direction in the xy plane. Therefore, the position of the A-scan image A _k in the xy plane is identified as the position of the pixel P _k is located in the xy plane and the intersection of A-scan images A _k.

Profile generator 2311, for each A-scan image A _k, total values (luminance values) of a plurality of pixels included in the A-scan image A _k, associates the integrated value obtained in the pixel P _k. Thereby, correspondence between the integrated value and a plurality of pixels _P 1 to P _K of a plurality of A-scan images _A 1 to A _K is obtained. When this correspondence is graphed, an integrated value profile P as shown in FIG. 6B is obtained. The horizontal axis of the integrated value profile P represents the position of the pixel corresponding to the plurality of A-scan images A ₁ to A _K, and the vertical axis represents the magnitude of the integrated value. In the integrated value profile P, the integrated value obtained from the A scan image A _k is associated with the pixel P _k . Such an integrated value profile is created for each frame constituting each phase image of a plurality of cross sections for which preliminary measurement has been performed. Thereby, an integrated value profile over time for each cross section is obtained.

  In this embodiment, the values of all the pixels included in the A scan image are integrated. However, it is also possible to configure to integrate only some pixel values of a plurality of pixels included in the A scan image. It is. That is, the profile generation unit 2311 only needs to be configured to integrate the pixel values of at least some of the plurality of pixels constituting the phase image frame. The case of targeting only some pixels will be described later.

(Arterial region specifying unit 2312)
A part Pa of the integrated value profile P corresponds to the blood vessel region Fa. When the blood vessel region Fa corresponds to a vein, the luminance value of the blood vessel region Fa changes little over time, but when the blood vessel region Fa corresponds to an artery, the luminance value of the blood vessel region Fa changes greatly over time. To do. Therefore, it is possible to determine whether the blood vessel passing through the cross section is an artery or a vein by analyzing the integrated value profile over time. Using such a fact, the arterial region specifying unit 2312 specifies an image region (arterial region) corresponding to the artery. An example of processing executed by the arterial region specifying unit 2312 will be described below.

In the blood vessel discrimination, the degree (size) of change in luminance value over time can be taken into consideration. In other words, the arterial region specifying unit 2312 can determine a blood vessel based on a change with time of the integrated value profile (variation with time of the integrated value). As a specific example, the arterial region specifying unit 2312 can obtain a difference between different accumulated value profiles included in the accumulated value profile over time, and determine a blood vessel based on the magnitude of the obtained difference. When the difference is relatively large, the blood vessel is determined as an artery. In addition, the arterial region specifying unit 2312 can obtain an evaluation value of the magnitude of change over time of the integrated value for each pixel position (for each pixel P _k ), and can determine a blood vessel based on the evaluation value. is there. When the change over time in the integrated value is relatively large, the blood vessel is determined to be an artery. Further, the arterial region specifying unit 2312 can obtain a statistical value (standard deviation, variance, etc.) of dispersion of integrated values in each integrated value profile, and can determine a blood vessel based on the statistical values. When the variation in the integrated value is relatively large, the blood vessel is determined as an artery.

  In the blood vessel discrimination, the magnitude (absolute value) of the luminance value can be taken into consideration. For example, the arterial region specifying unit 2312 can determine that the blood vessel is an artery when there is an integrated value profile including a group of pixels (blood vessel regions) associated with relatively large integrated values. In this example, the magnitude of the representative value in the integrated value profile is referred to. This representative value is, for example, the maximum value or the maximum value in the integrated value profile.

  In the above description, “relatively” refers to a comparison between the arterial region and the venous region. Whether or not a certain value is “relatively” large is determined, for example, by comparison with a threshold value for distinguishing between an arterial region and a venous region.

(Information generation unit 2313)
The information generation unit 2313 generates measurement site information for setting a target site for blood flow measurement based on the arterial region specified by the arterial region specification unit 2312. The form of the measurement site information is arbitrary.

  For example, the measurement site information may include information indicating whether the blood vessel passing through the cross-section for which the preliminary measurement has been performed is an artery or a vein. When two or more blood vessels pass through one cross section (that is, when two or more blood vessel regions are specified in the frame), the information generation unit 2313 determines whether each blood vessel is an artery or a vein. It is possible to generate information indicating whether or not. A specific example of the measurement site information will be described later.

(Blood flow measurement processing unit 232)
The blood flow measurement processing unit 232 executes processing of data acquired by blood flow measurement of a part set based on preliminary measurement. In this example, the blood flow measurement processing unit 232 obtains the inclination of the blood vessel of interest in the cross section of interest based on the data acquired by the first scan. Further, the blood flow measurement processing unit 232 obtains blood flow information related to the target blood vessel based on the inclination of the target blood vessel obtained based on the first scan and the data obtained by the second scan. The blood flow information includes, for example, a blood flow velocity and a blood flow volume. The blood flow measurement processing unit 232 includes a blood vessel region specifying unit 2321, an inclination calculating unit 2322, a blood flow velocity calculating unit 2323, a blood vessel diameter calculating unit 2324, and a blood flow rate calculating unit 2325.

(Vessel region specifying unit 2321)
The blood vessel region specifying unit 2321 specifies a blood vessel region corresponding to the target blood vessel in the tomographic image formed by the tomographic image forming unit 221. Further, the blood vessel region specifying unit 2321 specifies a blood vessel region corresponding to the target blood vessel in the phase image formed by the phase image forming unit 222. The blood vessel region is specified by analyzing the pixel value of each image (for example, threshold processing).

  When a tomographic image and a phase image are created from the same data, the blood vessel region in the tomographic image in which the cross-sectional shape is relatively clearly depicted is first executed, and the phase image corresponding to the identified blood vessel region is identified. The region can be specified using the natural registration of the tomographic image and the phase image described above. Even if the tomographic image and the phase image are created from different data, if the registration is possible directly or indirectly, the result of specifying the blood vessel region of one image is obtained. It can be used to specify the blood vessel region of the image.

(Inclination calculation unit 2322)
The inclination calculation unit 2322 calculates the inclination of the blood vessel Db of interest in the cross section of interest C2 based on the data acquired by the first scan. At this time, it is possible to further use data obtained by the second scanning. The inclination calculation unit 2322 calculates the inclination of the target blood vessel Db in the target cross section C2 based on the distance between cross sections and the result of specifying the blood vessel region. The distance between cross sections may include a distance between the cross section C11 and the cross section C12. Further, the distance between the cross sections may include a distance between the cross section C11 and the target cross section C2, and a distance between the cross section C12 and the target cross section C2.

  An example of a method for calculating the inclination of the target blood vessel Db will be described with reference to FIG. The tomographic images G11 and G12 are a tomographic image representing the cross section C11 to which the first scan is applied and a tomographic image representing the cross section C12, respectively. The tomographic image G2 is a tomographic image representing the cross section of interest C2 to which the second scanning is applied. Reference numerals V11, V12, and V2 indicate a blood vessel region in the tomographic image G11, a blood vessel region in the tomographic image G12, and a blood vessel region in the tomographic image G2, respectively. These blood vessel regions correspond to the cross section of the target blood vessel Db. In FIG. 7, the z coordinate axis is directed downward, which substantially coincides with the irradiation direction of the measurement light LS (the optical axis direction, the axial direction, and the A line direction of the optical path of the measurement light LS). . Also, let L be the interval between adjacent tomographic images (cross sections).

  In one example, the inclination calculating unit 2322 calculates the inclination U of the target blood vessel Db in the target cross section C2 based on the positional relationship between the three blood vessel regions V11, V12, and V2. This positional relationship is obtained, for example, by connecting three blood vessel regions V11, V12, and V2. Specifically, the inclination calculation unit 2322 identifies feature points of the three blood vessel regions V11, V12, and V2, and connects these feature points. As the feature points, there are a center position, a center of gravity position, an uppermost portion (a position having the smallest z coordinate value), a lowermost portion (a position having the largest z coordinate value), and the like. In addition, as a method of connecting these feature points, there are a method of connecting with a line segment, a method of connecting with an approximate curve (spline curve, Bezier curve, etc.), and the like.

  Further, the inclination calculation unit 2322 calculates the inclination U based on a line connecting these feature points. When the line segment is used, for example, the slope of the first line segment connecting the feature point of the blood vessel region V2 in the cross section of interest C2 and the feature point of the blood vessel region V11 in the cross section C11, and the feature point of the blood vessel region V2 The inclination U is calculated based on the inclination of the second line segment connecting the characteristic points of the blood vessel region V12 in the cross section C12. As an example of this calculation process, the average value of the slopes of two line segments can be obtained. Further, as an example of connecting with an approximate curve, the slope of the approximate curve at the intersection position of the approximate curve and the target cross section C2 can be obtained. Note that the cross-sectional distance L is used when embedding these tomographic images G11, G12, and G2 in the xyz coordinate system in the process of obtaining line segments and approximate curves.

  In this example, the blood vessel regions in three cross sections are considered, but the inclination can be obtained in consideration of the blood vessel regions in the two cross sections. As a specific example, the inclination U of the target blood vessel Db in the target cross section C2 can be obtained based on the blood vessel region V11 in the cross section C11 and the blood vessel region V12 in the cross section C12. Alternatively, the slope of the first line segment or the second line segment can be used as the slope U.

  The method of calculating the inclination of the blood vessel of interest in the cross section of interest is not limited to the above. For example, the following method can be applied. First, an OCT scan is performed on a cross section that intersects the cross section of interest and is along the blood vessel of interest. Next, a tomographic image is formed based on the data acquired by this OCT scan, and this tomographic image is segmented to identify an image region (layer region) corresponding to a predetermined tissue. The specified layer region is, for example, a layer region (ILM region) corresponding to the inner boundary film. The inner limiting membrane is a retinal tissue that defines the boundary between the retina and the vitreous body and is relatively clearly depicted. Further, a line segment that approximates the shape of the identified layer region is obtained, and its inclination is obtained. The inclination of the approximate line segment is expressed, for example, as an angle with respect to the z coordinate axis or as an angle with respect to the xy plane (that is, a plane orthogonal to the z coordinate axis).

(Blood velocity calculation unit 2323)
The blood flow velocity calculation unit 2323 calculates the blood flow velocity in the target section C2 of the blood flowing in the target blood vessel Db based on the time-series change of the phase difference obtained as the phase image. This calculation target may be a blood flow velocity at a certain point in time, or a time-series change (blood flow velocity change information) of this blood flow velocity. In the former case, for example, it is possible to selectively acquire the blood flow velocity in a predetermined time phase of the electrocardiogram (for example, the time phase of the R wave). The time range in the latter is the entire time or arbitrary part of the time when the target cross section C2 is scanned.

  When the blood flow velocity change information is obtained, the blood flow velocity calculator 2323 can calculate the statistical value of the blood flow velocity in the time range. The statistical values include an average value, standard deviation, variance, median value, maximum value, minimum value, maximum value, minimum value, and the like. It is also possible to create a histogram for blood flow velocity values.

  The blood flow velocity calculation unit 2323 calculates the blood flow velocity using the Doppler OCT method as described above. At this time, the inclination U of the target blood vessel Db in the target section C2 calculated by the inclination calculation unit 2322 is taken into consideration. Specifically, the inclination calculation unit 2322 uses the following expression.

here:
Δf represents the Doppler shift received by the scattered light of the measurement light LS;
n represents the refractive index of the medium (blood);
v represents the flow velocity (blood flow velocity) of the medium;
θ represents the angle formed by the incident direction of the measurement light LS and the direction of the medium flow (inclination U);
λ represents the center wavelength of the measurement light LS.

  In this embodiment, n and λ are known, Δf is obtained from the time-series change of the phase difference, and θ is obtained from the slope U (or θ is obtained as the slope U). By substituting these values into the equation (1), the blood flow velocity v is calculated.

(Vessel diameter calculator 2324)
The blood vessel diameter calculation unit 2324 calculates the diameter of the target blood vessel Db in the target cross section C2 by analyzing the fundus image or the OCT image. When the fundus image is used, the region of the fundus oculi Ef including the position of the cross section of interest C2 is imaged, and the cross section of interest C2 based on the fundus image obtained (for example, a color fundus image, a red free image). The diameter of the blood vessel Db of interest, that is, the diameter of the blood vessel region V2 is calculated. When an OCT image is used, this OCT image is, for example, a tomographic image formed based on the second scan or an image formed based on preliminary measurement. Such calculation of the blood vessel diameter is executed in the same manner as before.

(Blood flow calculation unit 2325)
The blood flow rate calculation unit 2325 calculates the flow rate of blood flowing in the target blood vessel Db based on the blood flow velocity calculation result and the blood vessel diameter calculation result. An example of this process will be described below.

  It is assumed that the blood flow in the blood vessel is a Hagen-Poiseille flow. Further, when the blood vessel diameter is w and the maximum value of the blood flow velocity is Vm, the blood flow rate Q is expressed by the following equation.

  The blood flow rate calculation unit 2325 substitutes the calculation result w of the blood vessel diameter by the blood vessel diameter calculation unit 2324 and the maximum value Vm based on the calculation result of the blood flow velocity by the blood flow velocity calculation unit 2323 into Expression (2). The blood flow rate Q is calculated.

(User interface 240)
The user interface 240 includes a display unit 241 and an operation unit 242. The display unit 241 includes the display device of the arithmetic control unit 200 and the display device 3. The operation unit 242 includes an operation device of the arithmetic control unit 200. The user interface 240 may include a device having a display function and an operation function, such as a touch panel.

[Operation]
The operation of the blood flow measuring device 1 will be described. FIG. 8 shows an example of the flow of operations performed by the blood flow measurement device 1. It is assumed that preparatory operations such as patient ID input, alignment, and focusing have already been performed.

(S1: Preliminary measurement)
First, the user or blood flow measurement device 1 sets a scan range for preliminary measurement. In setting the scan range, for example, an infrared observation image of the fundus oculi Ef acquired in real time or data of the fundus oculi Ef acquired in the past (fundus image, OCT image, SLO image, phase image, etc.) is referred to. The

  The blood flow measurement device 1 performs preliminary measurement on the set scan range (a plurality of cross sections). As an example, the set scan range is a three-dimensional area, and the raster scan of the three-dimensional area is repeatedly executed. The phase image forming unit 222 forms a phase image for each of the plurality of cross sections based on the data acquired by the preliminary measurement.

(S2: Generation of time series integrated value profile)
The profile generation unit 2311 generates a temporally integrated value profile for each cross-section for which preliminary measurement has been performed by integrating pixel values of each frame of each phase image formed in step S1 in the A-line direction.

(S3: Identification of arterial region)
The arterial region specifying unit 2312 specifies the arterial region by analyzing the temporally integrated value profile generated in step S2. If no arterial region is obtained, it is possible to return to the setting of the scan range in step S1. Here, a sufficiently wide scan range can be set from the beginning so as to obtain an arterial region. Further, by setting the scan range in the vicinity of the optic disc, the possibility of obtaining an arterial region can be increased.

(S4: Generation of measurement site information)
The information generation unit 2313 generates measurement site information for setting a target site for blood flow measurement based on the arterial region specified in step S3.

(S5: Display of information for setting the measurement site)
The control unit 210 causes the display unit 241 to display information (setting support information) for setting a target site for blood flow measurement based on the measurement site information generated in step S4. The setting support information may include information that enables discrimination between an artery and a vein. In particular, the setting support information may include information presenting the position of the artery.

  In one example, the control unit 210 displays a front image of the fundus oculi Ef and also displays setting support information that presents the arterial region in the front image in an identifiable manner. The front image is, for example, an infrared observation image acquired in real time or an image acquired in the past. The setting support information is, for example, information that is overlaid on the front image, and includes an arrow image that points to the artery region and an image of a predetermined display color that is arranged on the artery region.

(S6: Setting of attention cross section, etc.)
The user refers to the information displayed in step S5 and sets a cross section (target cross section C2) to be subjected to blood flow measurement. For example, the user designates a desired artery region (target blood vessel Db) in the front image by referring to the setting support information displayed together with the front image of the fundus oculi Ef.

  In this example, the attention section C2 is manually set, but the present invention is not limited to this. For example, the target blood vessel Db and the target cross section C2 can be automatically set based on the infrared observation image of the fundus oculi Ef and the measurement site information. The target blood vessel Db is set, for example, by selecting one of the arterial regions (for example, the thickest one). The attention section C2 is set, for example, at a position where the direction of the attention blood vessel Db is within a predetermined allowable range so as to be orthogonal to the traveling direction of the attention blood vessel Db.

  Furthermore, the user or the blood flow measurement device 1 (for example, the data processing unit 230) sets the cross sections C11 and C12 that are the targets of the first scan.

(S7: First scan of blood flow measurement)
The blood flow measurement device 1 executes the OCT scan of the cross sections C11 and C12 set in step S6 (first scan). The tomographic image forming unit 221 forms tomographic images G11 and G12 corresponding to the cross sections C11 and C12 based on the data acquired by the first scanning. The data processing unit 230 (the blood vessel region specifying unit 2321 and the inclination calculating unit 2322) calculates the inclination U of the target blood vessel Db in the target cross section C2. Note that when the inclination U is calculated in consideration of data acquired by the second scan, the inclination U is calculated after the second scan.

(S8: Second scan of blood flow measurement)
The blood flow measurement device 1 performs repetitive OCT scans of the cross section of interest C2 set in step S6 (second scan). The phase image forming unit 222 forms a phase image of the cross section of interest C2 based on the data acquired by the second scan. In addition, the tomographic image forming unit 221 forms a tomographic image of the cross section of interest C2 based on the data. The data processing unit 230 (blood vessel region specifying unit 2321, blood vessel diameter calculating unit 2324, etc.) obtains the diameter of the target blood vessel Db in the target cross section C2.

(S9: Generation of blood flow information)
The blood flow velocity calculation unit 2323 calculates the blood flow velocity in the cross section of interest C2 based on the slope U calculated based on the first scan in step S7 and the phase image acquired by the second scan in step S8. . Furthermore, the blood flow rate calculation unit 2325 calculates the flow rate of blood flowing in the target blood vessel Db based on the calculation result of the blood flow velocity and the calculation result of the blood vessel diameter obtained in step S8.

  The main control unit 211 causes the display unit 241 to display blood flow information including blood flow velocity calculation results, blood flow volume calculation results, and the like. In addition, the main control unit 211 stores blood flow information in the storage unit 212 in association with the patient ID. This is the end of the operation according to this example.

[Action / Effect]
The operation and effect of the blood flow measurement device according to the embodiment will be described.

  The blood flow measurement device according to the embodiment performs blood flow measurement of a living body (fundus Ef and the like) using OCT, and includes a data acquisition unit, a phase image formation unit, and a processing unit.

  The data acquisition unit acquires data by repeatedly scanning a plurality of cross sections of the living body. That is, the data acquisition unit performs preliminary measurement. In the above embodiment, the data acquisition unit includes a configuration for performing OCT, such as the OCT unit 100 and an optical element group arranged in the optical path of the measurement light LS.

  The phase image forming unit (222) forms a phase image in each of a plurality of cross sections for which preliminary measurement has been performed based on the data acquired by the data acquisition unit.

  The processing unit (preliminary measurement processing unit 231) integrates the values of at least some of the pixels in each frame of the phase image formed by the phase image forming unit, so that each of the plurality of cross-sections for which preliminary measurement has been performed is performed. Generate a cumulative value profile over time. Further, the processing unit generates measurement site information for setting a target site for blood flow measurement based on the generated temporal integration value profile.

  In the embodiment, the processing unit analyzes a temporal integrated value profile to specify an arterial region (arterial region specifying unit 2312), and information to generate measurement site information based on the specified arterial region And a generation unit (2313).

  Further, the region specifying unit may be configured to obtain information indicating the degree of change with time of the time-dependent integrated value profile by analyzing the time-dependent integrated value profile and specify the arterial region based on this information.

  Further, the region specifying unit may be configured to specify an arterial region based on the magnitude of the representative value in the temporal integrated value profile.

  The blood flow measurement device according to the embodiment may further include a front image acquisition unit, a display control unit, and an operation unit. The front image acquisition unit acquires a front image of the living body. In the above embodiment, the front image acquisition unit includes a configuration for photographing the fundus oculi Ef, such as the fundus camera unit 2. The front image acquisition unit may be configured to acquire a front image stored in a blood flow measurement device or another device. For example, the front image acquisition unit may be configured to acquire a front image from an image filing system through a network. The display control unit (control unit 210) displays the front image and the measurement site information on the display unit. The display means may be included in the blood flow measurement device or a display device connected thereto. The operation unit (242) is used to set a target cross section (target cross section C2) for blood flow measurement.

  According to such an embodiment, measurement site information is generated based on a phase image group acquired by performing an OCT scan of a plurality of cross sections, and a target site for blood flow measurement is set based on the measurement site information. be able to. Therefore, it is not necessary to perform trial and error for searching for a target blood vessel (blood vessel of interest) for blood flow measurement, and the target blood vessel can be set without depending on the user's experience. Therefore, it is possible to facilitate the setting of the target site for blood flow measurement and to shorten the time. The embodiment also contributes to improvement in accuracy and reproducibility of setting of the target blood vessel.

Second Embodiment
In the first embodiment, the values of all the pixels constituting the frame of the phase image are integrated in order to generate a temporally integrated value profile. On the other hand, in the second embodiment, a case will be described in which only some pixels in a frame of a phase image are integrated.

  A configuration example of this embodiment is shown in FIG. The blood flow measurement device of the present embodiment has substantially the same configuration as that of the first embodiment, but differs from the first embodiment in that the preliminary measurement processing unit 231 is provided with a layer region specifying unit 2314. Unless otherwise noted, reference is made to the drawings of the first embodiment.

  The layer region specifying unit 2314 specifies a layer region in the OCT image by analyzing the OCT image. The layer region is, for example, an image region corresponding to an arbitrary tissue of the fundus oculi Ef or an image region corresponding to a boundary between adjacent tissues. The layer region may be an image region corresponding to retinal tissue. Tissues that can be identified as layer layer regions include inner boundary membrane (ILM), nerve fiber layer (NFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner granule layer (INL), outer reticular layer ( OPL), outer granule layer (ONL), photoreceptor inner and outer segment junction (IS / OS), retinal pigment epithelium layer (RPE), Bruch's membrane (BM) choroid-sclera boundary (CSI), and the like.

  The process of dividing the OCT image into a plurality of layer regions is called segmentation. Segmentation is performed based on pixel values (luminance values) of a two-dimensional tomographic image or a three-dimensional image. Each layer structure of the fundus oculi Ef has a characteristic reflectance, and an image region of the layer structure also has a characteristic luminance value. In segmentation, a target image area is specified based on such characteristic luminance values.

  The layer region specifying unit 2314 performs segmentation of the frame of the phase image obtained by the preliminary measurement. Therefore, the layer region specifying unit 2314 can analyze only the phase image or both the phase image and the tomographic image. As an example of the latter, it is possible to perform segmentation on a tomographic image and reflect the result in a phase image. Furthermore, a blood vessel region can be specified based on the phase image, and a partial region (one or more layer regions) including the blood vessel region can be specified. For example, as shown in FIG. 10, the partial region Fb including the blood vessel region Fa is specified in the frame F.

  The profile generation unit 2311 generates an integrated value profile for the frame by integrating the values of pixels included in the layer region specified by the layer region specifying unit 2314 (for example, in the A line direction). In a plurality of frames, the integrated ranges may be the same or different.

  According to such an embodiment, it is possible to reduce noise included in the integrated value profile. For example, since the integrated value profile can be generated by excluding data of portions not related to the arterial / vein discrimination such as the vitreous body, the accuracy and accuracy of the arterial / vein determination are expected to be improved.

<Third Embodiment>
When two or more blood vessels are arranged side by side in the z direction, in OCT, only the data of the blood vessel closest to the retina surface is preferably acquired, and the data on the other blood vessels are often not acquired sufficiently. If the pixel values of the A scan image passing through such a part are integrated, the accuracy of the obtained integrated value may be low. In the present embodiment, a configuration in which such an inappropriate part is excluded and an integrated value profile is generated will be described.

  A configuration example of this embodiment is shown in FIG. The blood flow measurement device according to the present embodiment has substantially the same configuration as that of the first embodiment, but differs from the first embodiment in that the preliminary measurement processing unit 231 is provided with a partial region specifying unit 2315. Unless otherwise noted, reference is made to the drawings of the first embodiment.

  The partial area specifying unit 2315 specifies a partial area corresponding to a predetermined part of the eye E in the frame of the phase image obtained by the preliminary measurement. The predetermined part may include an inappropriate part as described above. The partial area specifying unit 2315 specifies the partial area by analyzing only the phase image or both the phase image and the tomographic image. As an example of the latter, the partial region specifying unit 2315 can specify a region corresponding to a predetermined part in the tomographic image, and can specify a partial region in the phase image corresponding to this region. Further, a blood vessel region may be specified based on the phase image, and it may be determined whether some of the specified blood vessel regions are arranged in the z direction.

  The profile generation unit 2311 generates an integrated value profile for the frame by integrating (for example, in the A-line direction) pixel values included in regions other than the partial region specified by the partial region specifying unit 2315. In a plurality of frames, the integrated ranges may be the same or different.

  According to such an embodiment, as in the second embodiment, it is possible to reduce noise included in the integrated value profile.

<Modification>
The configuration described above is merely an example of an embodiment of the present invention. Therefore, arbitrary modifications (omitted, replacement, addition, etc.) within the scope of the present invention can be made.

  For example, in the above exemplary embodiment, data is acquired by repeatedly scanning a plurality of cross sections of a living body, a phase image in each of the plurality of cross sections is formed, and a temporally integrated value profile in each of the plurality of cross sections is obtained. The measurement part information is generated based on it. However, the number of cross sections to be processed is not limited to two or more and may be one. In other words, the embodiment repeatedly scans a “single” cross section of a living body to acquire data, forms a phase image in this cross section, generates a temporal integrated value profile in this cross section, and generates this temporal integrated value. The measurement part information may be generated based on the profile.

  In addition, considering that the blood flow velocity in any cross section is the same for both arteries and veins, and the pulsation state is the same, distinguishing between the arterial region and the venous region in a single cross section Can be done. Even in that case, the arterial region and the vein region can be specified in the same manner as in the above embodiment. However, when processing is applied to a single cross section, only the blood vessels that intersect this cross section can be identified. It is necessary to apply processing to a number of cross sections.

  As described above, in the blood flow measurement device according to the embodiment, the data acquisition unit may be configured to acquire data by repeatedly scanning one or more cross sections of the living body, and the phase image forming unit may acquire the acquired data. A phase image in each of the one or more cross-sections, and the processing unit integrates the values of at least some of the pixels in each frame of the phase image to time over each of the one or more cross-sections. A cumulative integrated value profile may be generated, and measurement site information for blood flow measurement may be generated based on the temporal integrated value profile.

  Also in this configuration, the processing unit can generate a temporally integrated value profile by segmentation and integration of pixel values of layer regions, as in the above embodiment. Alternatively, the processing unit can generate a temporally integrated value profile by specifying partial areas in the phase image and integrating pixel values of areas other than the partial areas, as in the above embodiment. Furthermore, it is possible to display the front image of the living body and the measurement site information, and accept the setting of the target cross section for blood flow measurement.

  In the above exemplary embodiment, the arterial region is selectively specified in order to set the target site for blood flow measurement, but the vein region can also be specified. That is, in the embodiment, the region specifying unit may be configured to specify at least one of the arterial region and the venous region by analyzing the integrated value profile over time. The vein region can be identified in the same manner as the arterial region. For example, the region specifying unit is configured to obtain information indicating the degree of change over time (variation of integrated values over time) by analyzing the integrated value profile over time, and specify a vein region based on this information May be. Alternatively, the region specifying unit may be configured to specify the vein region based on the size of the representative value (for example, the maximum value, the maximum value, etc.) in the temporal integrated value profile.

  The type of blood vessel as a specific target can be selected manually or automatically. For example, when it is effective to consider arterial blood flow for diagnosis or screening, an artery is selected as a specific target. Conversely, when it is effective to consider venous blood flow for diagnosis or screening, an artery is selected as a specific target. In addition, when it is necessary to analyze both arterial blood flow and venous blood flow sent to the whole body for diagnosis and screening, both the artery and vein are selected as specific objects. The region specifying unit operates to specify a region corresponding to the artery and / or vein selected as the specifying target. The blood vessel discrimination according to the embodiment can be applied to other than blood flow measurement. For example, blood vessel discrimination can be applied to determine the shape and distribution of arteries and veins.

  In this manner, the information generation unit can generate measurement site information based on at least one of the arterial region and the vein region specified by the region specifying unit.

  In the above exemplary embodiment, the values of at least some of the pixels in the frame (two-dimensional cross section) of the phase image are integrated in the A-line direction in order to generate a temporal integration value profile. However, the direction in which the pixel values are integrated is not limited to the A line direction. For example, pixel values can be integrated in a direction orthogonal to the A-line direction (horizontal scan direction) in the frame. Alternatively, the pixel values can be integrated in any direction different from the A line direction and the horizontal scan direction.

  The frame of the phase image is not limited to a two-dimensional section. For example, when a phase image of a three-dimensional region is obtained, it is possible to generate a temporal pixel value profile by integrating pixel values in an arbitrary direction in the three-dimensional region.

  Further, when the phase image frame is a two-dimensional cross section, the two-dimensional cross section is not limited to a plane. For example, when circle scanning is applied, the frame of the phase image corresponds to a cylindrical cross section. In such a case, it is possible to generate a temporally integrated value profile by integrating pixel values in an arbitrary direction in the cross section. More generally, the direction in which pixel values are integrated is not limited to a linear direction (a constant direction), and may be a direction along an arbitrary path such as a curved direction.

  In addition, pixel values can be integrated in a plurality of directions in one frame. For example, it is possible to generate a plurality of temporal integration value profiles by integrating pixel values in a plurality of directions, respectively. Then, it is possible to select and use one of a plurality of time-integrated value profiles, or use data obtained by integrating two or more of the plurality of time-integrated value profiles.

1 Blood Flow Measurement Device 100 OCT Unit 222 Phase Image Forming Unit 231 Preliminary Measurement Processing Unit

Claims (9)

An ophthalmic image processing apparatus including a data processing unit that processes an image acquired from an eye to be examined using an optical coherence tomography (OCT) optical system,
The data processing unit generates information indicating whether the blood vessel is an artery or a vein based on an image including an image region corresponding to a blood vessel of the eye to be examined. The ophthalmic image processing apparatus according to claim 1, wherein the data processing unit generates the information based on a luminance value in the image. The ophthalmic image processing apparatus according to claim 2, wherein the data processing unit generates the information based on a luminance value in the image. The ophthalmic image processing apparatus according to claim 1, wherein the data processing unit generates the information based on a partial region of the image. The data processing unit identifies two or more image regions from the image, and generates the information for blood vessels corresponding to each of the identified two or more image regions. The ophthalmic image processing apparatus according to any one of the above. The said data processing part performs the segmentation of the said image, The said information is produced | generated based on either of the one or more partial area specified by the said segmentation. Ophthalmic image processing device. The ophthalmic image processing apparatus according to claim 1, further comprising: a control unit that causes a display unit to display information based on the information generated by the data processing unit. The ophthalmic image processing apparatus according to claim 7, wherein the control unit displays information based on the information generated by the data processing unit together with a front image of the fundus of the eye to be examined. The ophthalmic image processing apparatus according to claim 8, wherein the control unit displays information based on the information generated by the data processing unit together with an angiographic image of the fundus of the eye to be examined.