Ophthalmic device, control method therefor, program, and recording medium

Abstract

A scan unit of an ophthalmic device according to an embodiment of the present invention collects data by applying an iterative scan to a target blood vessel of a fundus. A phase image generation unit generates a phase image from the data. A blood vessel region specification unit specifies a blood vessel region from the phase image. A future time point estimation unit applies time series analysis to the blood vessel region to estimate a future time point corresponding to a predetermined heartbeat time phase. A scan control unit controls the scan unit so as to collect first data by applying a first scan to a first cross-section of the target blood vessel before the future time point is reached, and to collect second data by applying a second scan to a second cross-section of the target blood vessel when the future time point is reached. On the basis of the first data, an angle calculation unit calculates a Doppler angle in OCT blood flow measurement, such calculation performed with respect to the target blood vessel. On the basis of the second data and the Doppler angle, a blood flow dynamic state information generation unit generates information on the blood flow dynamic state of the target blood vessel.

Description

Ophthalmic apparatus, its control method, program, and recording medium

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 557,720, entitled "OPHTHALMIC OPTICAL COHERENCE TOMOGRAPHY," filed February 26, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to an ophthalmic apparatus, a control method thereof, a program, and a recording medium.

[0003] Various imaging modalities are used in ophthalmology practice, including fundus cameras, scanning laser ophthalmoscopy (SLO), slit lamp microscopes, and optical coherence tomography (OCT). OCT can be used for both structural and functional imaging.

[0004] Structural imaging using OCT is a technique for representing the spatial distribution of OCT signal intensity, which varies depending on the structure of a test object, as an image. Images generated by this technique are called OCT intensity images or simply intensity images.

[0005] OCT blood flow measurement is one of the functional imaging techniques using OCT. OCT blood flow measurement is a Doppler measurement that uses OCT to determine blood flow dynamics, and is also called Doppler OCT. OCT blood flow measurement is a technique that repeatedly scans the cross section of a blood vessel with OCT measurement light to collect a data set, and then determines the Doppler signal due to blood flow from the difference in this data set. It also determines the angle (Doppler angle) between the blood vessel and the OCT measurement light, thereby determining the magnitude of retinal blood flow velocity. Furthermore, the blood flow volume can be calculated by multiplying the obtained blood flow velocity by the cross-sectional area of ​​the blood vessel. In the field of ophthalmology, OCT blood flow measurement is typically applied to blood vessels in the fundus, particularly retinal blood vessels. However, OCT blood flow measurement of choroidal blood vessels has also been reported.

[0006] U.S. Pat. No. 1,1980,419 U.S. Pat. No. 8,175,685 U.S. Pat. No. 1,1944,382

[0007] An object of the present disclosure is to improve fundus hemodynamic measurement using Doppler OCT.

[0008] An ophthalmic apparatus according to some embodiments performs optical coherence tomography blood flow measurement to measure blood flow dynamics in blood vessels at the fundus of the eye. The ophthalmic apparatus includes a scanning unit, a phase image generating unit, a vascular region identifying unit, a future time point estimating unit, a scan control unit, an angle calculating unit, and a blood flow dynamics information generating unit. The scanning unit is configured to collect data by repeatedly scanning a blood vessel of interest at the fundus of the eye to be examined. The phase image generating unit is configured to process the data collected by the scanning unit to generate a phase image. The vascular region identifying unit is configured to identify a blood vessel region in the phase image. The future time point estimating unit is configured to estimate a future time point corresponding to a predetermined cardiac phase by applying time series analysis to the blood vessel region identified from the phase image. The scan control unit is configured to control the scanning unit to apply a first scan to a first cross-section of the blood vessel of interest to collect first data before the estimated future time point arrives, and to control the scanning unit to apply a second scan to a second cross-section of the blood vessel of interest to collect second data when the future time point arrives. The angle calculation unit is configured to calculate a Doppler angle in optical coherence tomography blood flow measurement for the blood vessel of interest based on first data collected in the first scan. The hemodynamic information generation unit is configured to generate hemodynamic information for the blood vessel of interest based on second data collected in the second scan and the Doppler angle calculated by the angle calculation unit.

[0009] According to some embodiments, it is possible to improve fundus hemodynamic measurements using Doppler OCT.

[0010] FIG. 1 is a schematic diagram showing a configuration of an ophthalmic apparatus according to a non-limiting embodiment. FIG. 2 is a schematic diagram showing a configuration of an ophthalmic apparatus according to a non-limiting embodiment. FIG. 3 is a schematic diagram showing a configuration of an ophthalmic apparatus according to a non-limiting embodiment. FIG. 4 is a schematic diagram showing a configuration of an ophthalmic apparatus according to a non-limiting embodiment. FIG. 5 is a schematic diagram showing a configuration of an ophthalmic apparatus according to a non-limiting embodiment. FIG. 6 is a schematic diagram showing a configuration of an ophthalmic apparatus according to a non-limiting embodiment. FIG. 7 is a schematic diagram showing a configuration of an ophthalmic apparatus according to a non-limiting embodiment. FIG. 8 is a schematic diagram showing a configuration of an ophthalmic apparatus according to a non-limiting embodiment. FIG. 9 is a schematic diagram showing a configuration of an ophthalmic apparatus according to a non-limiting embodiment. FIG. 10 is a schematic diagram showing a configuration of an ophthalmic apparatus according to a non-limiting embodiment. FIG. 11 is a schematic diagram showing a configuration of an ophthalmic apparatus according to a non-limiting embodiment. FIG. 12 is a schematic diagram showing a configuration of an ophthalmic apparatus according to a non-limiting embodiment. FIG. 13 is a schematic diagram showing a configuration of an ophthalmic apparatus according to a non-limiting embodiment. FIG. 14 is a flowchart showing the operation of an ophthalmic apparatus according to a non-limiting embodiment.

[0011] Several non-limiting embodiments of the present disclosure will be described. In the present disclosure, embodiments of an ophthalmic device (e.g., an ophthalmic blood flow measuring device, an ophthalmic imaging device, etc.), embodiments of a method for controlling an ophthalmic device, embodiments of a program, and embodiments of a recording medium will be described. However, the categories of embodiments of the present disclosure are not limited to these.

[0012] The embodiments according to the present disclosure can be employed to solve problems that arise in measuring the dynamics of fundus hemodynamics using Doppler OCT. There are various problems in measuring the dynamics of fundus hemodynamics using Doppler OCT.

[0013] Some embodiments of the present disclosure are intended to improve the quality of processes and operations related to fundus hemodynamic measurement, and in particular, to optimize the start point of measurement, although the purpose of the present disclosure is not limited thereto.

[0014] Generally, fundus hemodynamic measurements collect data over at least one cardiac cycle to determine hemodynamics in all cardiac phases. To achieve this, data is collected for a time (e.g., 2 seconds) significantly longer than a standard cardiac cycle. Alternatively, data over one cardiac cycle can be collected while monitoring the subject's heartbeat using a biometric monitor such as an electrocardiograph. Using an electrocardiograph is advantageous in that it shortens measurement time and reliably collects data for one cardiac cycle. However, it has disadvantages in that it requires the preparation of an electrocardiograph and complicates the testing process. An objective of some embodiments is to provide a fundus hemodynamic measurement method that can shorten measurement time and reliably collect data without using a biometric monitor. It should be apparent to those skilled in the art from this disclosure that problems that can be addressed by utilizing the technology disclosed herein are not limited to those described above.

[0015] <Embodiments of Ophthalmic Apparatus> Several non-limiting aspects of an ophthalmic apparatus according to an embodiment will be described. The ophthalmic apparatus according to the embodiment has a function of performing OCT blood flow measurement and a function of processing data obtained by the OCT blood flow measurement.

[0016] The ophthalmic device according to the embodiment mainly described in the present disclosure functions as an OCT device capable of performing OCT blood flow measurement (OCT scan and image generation processing). In some other embodiments, the ophthalmic device may not be capable of performing at least a part of the processing of OCT blood flow measurement.

[0017] The OCT method may be any method, for example, spectral domain OCT or swept-source OCT. Spectral domain OCT is a method in which light from a low-coherence light source is split into measurement light and reference light, return light of the measurement light from the test object is superimposed on the reference light to generate interference light, the spectral distribution of the interference light is detected with a spectrometer, and the detected spectral distribution is subjected to processing such as Fourier transform to construct an image. Swept-source OCT is a method in which light from a tunable light source is split into measurement light and reference light, return light of the measurement light from the test object is superimposed on the reference light to generate interference light, the interference light is detected with a photodetector (such as a balanced photodiode), and detection data collected in response to wavelength sweeping and scanning of the measurement light is subjected to processing such as Fourier transform to construct an image. That is, spectral domain OCT is an OCT method that acquires a spectral distribution by spatial division, while swept-source OCT is an OCT method that acquires a spectral distribution by time division. It should be noted that other OCT methods, such as time domain OCT, may also be used.

[0018] The ophthalmic device according to the embodiment mainly described in the present disclosure has a function as a fundus camera capable of photographing the fundus of the eye. In some other embodiments, the ophthalmic device may have a function as any ophthalmic imaging modality, such as an SLO, a slit lamp microscope, or a surgical microscope, in addition to or instead of the function as a fundus camera.

[0019] In this disclosure, unless otherwise specified, no distinction is made between "image data" and "images" that are visual information based on the image data. Furthermore, unless otherwise specified, no distinction is made between a site or tissue of the subject's eye and its image (image data).

[0020] An ophthalmologic apparatus according to some exemplary embodiments may not have a fundus imaging function. Such an ophthalmologic apparatus may have a function of acquiring a front image of the fundus from a storage device or a recording medium. A typical example of a storage device is a medical image archiving system (medical image filing system). A typical example of a recording medium is a hard disk drive or an optical disk.

[0021] At least a portion of the functionality of elements of embodiments of the present disclosure is implemented using circuitry or processing circuitry. The circuitry or processing circuitry may be a general-purpose processor, a special-purpose processor, an integrated circuit, a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), an Application Specific Integrated Circuit (ASIC), a programmable logic device (e.g., a Simple Programmable Logic Device (SPLD), a Complex Programmable Logic Device (CPLD), a Field Programmable Gate Array (FPGA)), or a combination of these devices configured and / or programmed to perform at least some of the disclosed functions. Array), conventional circuitry, and any combination thereof. A processor is considered to be processing circuitry or circuitry, including transistors and / or other circuitry. In this disclosure, circuitry, unit, means, or similar terms refers to hardware that performs at least a portion of the disclosed functions or hardware that is programmed to perform at least a portion of the disclosed functions. The hardware may be hardware disclosed herein or known hardware that is programmed and / or configured to perform at least a portion of the described functions. In the case of a processor, where the hardware can be considered to be a type of circuitry, circuitry, unit, means, or similar terms refers to a combination of hardware and software, and the software is used to configure the hardware and / or processor.

[0022] The configuration of an exemplary ophthalmic apparatus is shown in Figures 1 to 4. The ophthalmic apparatus 1 of this example includes a fundus camera unit 2, an OCT unit 100, and an arithmetic and control unit 200. The fundus camera unit 2 is provided with elements of a fundus camera capable of photographing the fundus and the anterior segment, and elements of an OCT scanner. The OCT unit 100 is provided with elements of an OCT scanner. The arithmetic and control unit 200 includes one or more processors configured to perform various processes (such as calculation, analysis, and control).

[0023] The fundus camera unit 2 will now be described. The fundus camera unit 2 includes an optical system for photographing the fundus Ef (and the anterior segment) of the subject's eye E. The digital image acquired by the fundus camera unit 2 is typically a front image. The fundus camera unit 2 can acquire observation images by video capture using near-infrared fixed light as illumination light, and can acquire photographed images by capture using visible flash light as illumination light, for example.

[0024] The fundus camera unit 2 includes an illumination optical system 10 and an imaging optical system 30. The illumination optical system 10 irradiates illumination light onto the subject's eye E. The imaging optical system 30 detects return light of the illumination light irradiated onto the subject's eye E. In other words, the imaging optical system 30 photographs the subject's eye E illuminated by the illumination light. OCT measurement light provided from the OCT unit 100 is guided to the subject's eye E through an optical path within the fundus camera unit 2. Return light of the OCT measurement light applied to the subject's eye E is guided to the OCT unit 100 through an optical path within the fundus camera unit 2.

[0025] The observation illumination light output from the observation light source 11 of the illumination optical system 10 is reflected by the concave mirror 12, passes through the condenser lens 13, and passes through the visible cut filter 14 to become near-infrared light. It is then focused near the imaging light source 15, reflected by the mirror 16, and passed through the relay lens system 17, the relay lens 18, the aperture 19, and the relay lens system 20 to be guided to the perforated mirror 21. It is reflected by the mirror portion around the central hole of the perforated mirror 21, passes through the dichroic mirror 46, is refracted by the objective lens 22, and is projected onto the subject's eye E (fundus Ef). The return light of the observation illumination light projected onto the subject's eye E is refracted by the objective lens 22, passes through the dichroic mirror 46, passes through the central hole of the perforated mirror 21, passes through the dichroic mirror 55, passes through the photographing focusing lens 31, is reflected by the mirror 32, passes through the half mirror 33A, is reflected by the dichroic mirror 33, and is imaged on the light-receiving surface of the image sensor 35 by the imaging lens 34. The image sensor 35 detects the return light at regular time intervals (frame rate). The focus of the photographing optical system 30 is adjusted according to the photographing region.

[0026] The imaging illumination light output from the imaging light source 15 is projected onto the fundus oculi Ef along the same path as the observation illumination light. The return light of the imaging illumination light from the subject's eye E is guided to the dichroic mirror 33 along the same path as the return light of the observation illumination light, passes through the dichroic mirror 33, is reflected by a mirror 36, and is imaged by an imaging lens 37 on the light-receiving surface of an image sensor 38.

[0027] The liquid crystal display (LCD) 39 displays a fixation target (fixation target image) for guiding and fixing the line of sight. The light beam output from the liquid crystal display 39 is reflected by the half mirror 33A, reflected by the mirror 32, passes through the photographing focusing lens 31 and the dichroic mirror 55, passes through the central hole of the perforated mirror 21, passes through the dichroic mirror 46, is refracted by the objective lens 22, and is projected onto the fundus Ef. This allows the subject to visually recognize the fixation target.

[0028] The alignment optical system 50 generates an alignment index for aligning the ophthalmic apparatus 1 with respect to the subject's eye E. Alignment light output from a light-emitting diode (LED) 51 passes through an aperture 52, an aperture 53, and a relay lens 54, is reflected by a dichroic mirror 55, passes through the central hole of the perforated mirror 21, transmits through the dichroic mirror 46, and is projected onto the subject's eye E via the objective lens 22. The return light of the alignment light from the subject's eye E is guided to the image sensor 35 via the same path as the return light of the observation illumination light. Manual alignment or automatic alignment can be performed by referring to the received light image (alignment index image).

[0029] The focusing optical system 60 generates a split index used for focus adjustment of the subject's eye E. The focusing optical system 60 moves along the optical path (illumination optical path) of the illumination optical system 10 in conjunction with movement of the photographing focusing lens 31 along the optical path (photography optical path) of the photographing optical system 30. The reflecting rod 67 is inserted into and removed from the illumination optical path. When performing focus adjustment, the reflective surface of the reflecting rod 67 is tilted relative to the illumination optical path. The focusing light output from the LED 61 passes through the relay lens 62, is split into two beams by the split index plate 63, passes through the two-hole diaphragm 64, is reflected by the mirror 65, is once imaged and reflected by the condenser lens 66 on the reflective surface of the reflecting rod 67, passes through the relay lens 20, is reflected by the perforated mirror 21, passes through the dichroic mirror 46, and is projected onto the subject's eye E via the objective lens 22. The returning light of the focusing light from the subject's eye E is guided to the image sensor 35 along the same path as the returning light of the alignment light. By referring to the received light image (split target image), manual focusing and autofocusing can be performed.

[0030] If the subject's eye E is highly hyperopic, a diopter correction lens 70 (plus lens) is placed in the photographing optical path between the perforated mirror 21 and the dichroic mirror 55. On the other hand, if the subject's eye E is highly myopic, a diopter correction lens 71 (minus lens) is placed.

[0031] The dichroic mirror 46 combines the optical path for imaging by the fundus camera unit 2 with the optical path for OCT (measurement arm). The dichroic mirror 46 reflects light in the wavelength band for OCT and transmits light in the wavelength band for imaging by the fundus camera unit 2. The measurement arm is provided with, in order from the OCT unit 100 side, a collimator lens unit 40, a retroreflector 41, a dispersion compensation member 42, an OCT focusing lens 43, an optical scanner 44, and a relay lens 45. The retroreflector 41 is movable along the optical path of the OCT measurement light incident thereon and is used to correct the optical path length according to the axial length and adjust the interference state. The dispersion compensation member 42 is used for dispersion compensation between the measurement arm and the reference arm. The OCT focusing lens 43 is movable along the measurement arm and is used to adjust the focus of the measurement arm. Focus adjustment of the ophthalmologic apparatus 1 is performed by coordination of movement of the imaging focusing lens 31, movement of the focusing optical system 60, and movement of the OCT focusing lens 43. The optical scanner 44 is positioned at a position substantially conjugate with the pupil of the subject's eye E through alignment, and changes the traveling direction of the OCT measurement light. The optical scanner 44 is, for example, a galvano scanner capable of two-dimensional scanning.

[0032] The OCT unit 100 will now be described. The OCT unit 100 shown in FIG. 2 is equipped with a spectral domain OCT optical system. This OCT optical system includes an interference optical system. This interference optical system splits light from a low-coherence light source (broadband light source) into measurement light LS (OCT measurement light) and reference light LR, and generates interference light LC by superimposing the return light of the measurement light LS projected onto the subject's eye E on the reference light LR. The generated interference light LC is detected by a spectroscope 130. This provides a signal indicating the spectral distribution of the interference light LC. This detection signal is sent to the arithmetic and control unit 200.

[0033] The light source unit 101 outputs broadband low-coherence light L0. The light source unit 101 includes an optical output device such as a superluminescent diode (SLD), an LED, or a semiconductor optical amplifier (SOA). The low-coherence light L0 output from the light source unit 101 is guided by an optical fiber 102 to a polarization controller 103 where its polarization state is adjusted, and then guided by an optical fiber 104 to a fiber coupler 105 where it is split into a measurement light LS and a reference light LR. The measurement light LS is guided by a measurement arm, and the reference light LR is guided by a reference arm.

[0034] The reference light LR is guided by an optical fiber 110 to a collimator 111 and converted into a parallel beam, passes through an optical path length correction member 112 for compensating for the optical distance between the measurement arm and the reference arm, passes through a dispersion compensation member 113 for compensating for dispersion between the measurement arm and the reference arm, and is then guided to a retroreflector 114. The retroreflector 114 is movable along the optical path of the reference light LR incident thereon and is used to correct the optical path length according to the axial length and adjust the interference state. The reference light LR that has passed through the retroreflector 114 passes through the dispersion compensation member 113 and the optical path length correction member 112 and is converted from a parallel beam into a focused beam by a collimator 116, is guided through an optical fiber 117 to a polarization controller 118 for adjusting its polarization state, is guided through an optical fiber 119 to an attenuator 120 for adjusting its light intensity, and reaches a fiber coupler 122 through an optical fiber 121.

[0035] On the other hand, the measurement light LS is guided through the optical fiber 127 to the collimator lens unit 40, where it is converted into a parallel beam, passes through the retroreflector 41, the dispersion compensation member 42, the OCT focusing lens 43, the optical scanner 44, and the relay lens 45, is reflected by the dichroic mirror 46, is refracted by the objective lens 22, and is projected onto the subject's eye E. The measurement light LS is scattered and reflected at various depth positions in the subject's eye E. Return light of the measurement light LS from the subject's eye E travels in the opposite direction through the measurement arm, is guided to the fiber coupler 105, and reaches the fiber coupler 122 via the optical fiber 128.

[0036] The fiber coupler 122 generates interference light LC by superimposing the measurement light LS incident via the optical fiber 128 and the reference light LR incident via the optical fiber 121. The generated interference light LC is guided to the spectrometer 130 via the optical fiber 129. In a non-limiting example, the spectrometer 130 converts the incident interference light LC into a parallel beam using a collimator lens, resolves the parallel beam of interference light LC into multiple spectral components using a diffraction grating, and projects the multiple spectral components generated by the diffraction grating onto an image sensor via a lens. This image sensor is, for example, a line sensor, and detects the multiple spectral components of the interference light LC to generate an electrical signal (detection signal). The generated detection signal contains information about the spectral distribution of the interference light LC and is sent to the arithmetic and control unit 200.

[0037] The OCT unit 100 in FIG. 2 described above employs a spectral domain OCT system. When swept-source OCT is used, the light source unit 101 includes a tunable light source (e.g., a near-infrared tunable laser) that rapidly changes the wavelength of emitted light. Furthermore, in the swept-source OCT optical system, interference light LC, generated by superimposing the measurement light LS and the reference light LR, is split at a predetermined splitting ratio (e.g., 1:1) to generate a pair of interference light beams, which are then detected by a photodetector. The photodetector includes a balanced photodiode. The balanced photodiode includes a pair of photodetectors that respectively detect the pair of interference light beams and outputs the difference between the pair of detection signals obtained by the pair of photodetectors. The photodetector sends this difference signal to a data acquisition system (DAQ). A clock is supplied to the data acquisition system from the light source unit 101. This clock is generated in the light source unit 101 in synchronization with the output timing of each wavelength swept within a predetermined wavelength range by the tunable light source. For example, the light source unit 101 splits light of each output wavelength to generate two split lights, optically delays one of the split lights, and then combines the two split lights, detects the resulting combined light, and generates a clock based on the detection signal. The data collection system samples the detection signal (differential signal) input from the photodetector using the clock provided by the light source unit 101. The data obtained by this sampling is provided for processing such as image generation.

[0038] In the examples shown in FIGS. 1 and 2 , optical path length changing elements (retroreflectors 41 and 114) are provided in both the measurement arm and the reference arm, but only one of them may be provided. Furthermore, the optical path length changing elements are not limited to retroreflectors. For example, the optical path length changing element in the reference arm may be a movable reflecting member (reference mirror). More generally, the ophthalmic device according to the present disclosure includes an element configured to relatively change the measurement arm length and the reference arm length (i.e., an element configured to change the optical path length difference between the measurement arm and the reference arm), and this element can be used to move the coherence gate position.

[0039] The arithmetic and control unit 200 will be described. The arithmetic and control unit 200 executes various processes, such as controlling each component of the ophthalmologic apparatus 1, various calculations, and various analyses. For example, the arithmetic and control unit 200 performs signal processing, such as Fourier transform, on the spectral distribution (interference signal, interferogram) acquired by the spectroscope 130 to calculate a reflection intensity profile of a line (A-line) extending in the depth direction (z direction) at each projection position of the measurement light LS. Furthermore, the arithmetic and control unit 200 generates image data by imaging the reflection intensity profile of each A-line. The arithmetic and control unit 200 may perform the same calculation process as image generation using conventional spectral domain OCT. The arithmetic and control unit 200 includes, for example, a processor, RAM, ROM, a hard disk drive, a communication interface, etc. Various computer programs are stored in the storage device, such as the hard disk drive. The arithmetic and control unit 200 may also include an operation device, an input device, a display device, etc.

[0040] The user interface 240 shown in FIG. 3 will be described. The user interface 240 has a display unit 241 and an operation unit 242. The display unit 241 includes, for example, the display device 3 of FIG. 1. The operation unit 242 includes various operation devices and input devices. The user interface 240 may include a touch panel. In some exemplary embodiments, at least a portion of the user interface is provided as a peripheral device connected to the ophthalmologic apparatus 1.

[0041] The moving mechanism 150 shown in Fig. 3 will be described. The moving mechanism 150 is configured to move the optical system of the ophthalmologic apparatus 1. The moving mechanism 150 moves, for example, at least the fundus camera unit 2 three-dimensionally.

[0042] The data input / output unit 290 shown in FIG. 3 will be described. The data input / output unit 290 inputs data to the ophthalmologic apparatus 1 and outputs data from the ophthalmologic apparatus 1. A non-limiting example of the data input / output unit 290 has a function for communicating with an external device (not shown). The communication unit 290 includes a communication interface according to the connection configuration with the external device. The external device may be, for example, any ophthalmologic apparatus. The external device may also be any information processing device, such as a Hospital Information System (HIS) server, a DICOM (Digital Imaging and Communication in Medicine) server, a doctor's terminal, a mobile terminal, a personal terminal, or a cloud server. Some exemplary examples of the data input / output unit 290 include a device (data reader) that reads information from a recording medium and a device (data writer) that writes information to the recording medium. The data input / output unit 290 may be, but is not limited to, the above.

[0043] The processing system (arithmetic and control system) of the ophthalmologic apparatus 1 will now be described. An example of the configuration of the processing system is shown in Figures 3 and 4. The control unit 210 and the data processing unit 230 are provided in the arithmetic and control unit 200.

[0044] The control unit 210 includes a processor and controls each unit of the ophthalmic apparatus 1. The control unit 210 includes a main control unit 211 and a memory unit 212. The main control unit 211 includes a processor and is configured to control each element of the ophthalmic apparatus 1 (including the elements shown in FIGS. 1 to 3). The main control unit 211 may also be configured to be able to control apparatuses, devices, and systems connected to the ophthalmic apparatus 1. The functions of the main control unit 211 are realized, for example, by cooperation between hardware including circuits and control software. The memory unit 212 stores various types of data. The memory unit 212 includes a storage device such as a hard disk drive or a solid state drive.

[0045] Several controls executed by the main controller 211 will be described. The main controller 211 controls an imaging focusing driver (not shown) to synchronously move the imaging focusing lens 31 and the focus optical system 60. The main controller 211 controls a retroreflector (RR) driver 41A to move the retroreflector 41 of the measurement arm. The main controller 211 controls an OCT focusing driver 43A to move the OCT focusing lens 43 of the measurement arm. The main controller 211 controls the optical scanner 44 to deflect the measurement light LS according to a preset scan pattern. The main controller 211 controls a retroreflector (RR) driver 114A to move the retroreflector 114 of the reference arm. The main controller 211 controls a moving mechanism 150 to move the optical system (e.g., the fundus camera unit 2 and the OCT unit 100).

[0046] The data processing unit 230 performs various types of data processing. For example, the data processing unit 230 applies various types of processing to images (fundus images, anterior segment images, etc.) acquired by the fundus camera unit 2. The data processing unit 230 also applies various types of processing to images acquired using OCT scanning (OCT images). The data processing unit 230 includes a processor. The data processing unit 230 is realized, for example, by cooperation between hardware including circuits and data processing software.

[0047] The data processing unit 230 includes an image generation unit 220. The image generation unit 220 processes data collected by applying an OCT scan to the fundus Ef of the subject's eye E to generate OCT image data. The image generation unit 220 includes a processor. The functions of the image generation unit 220 are realized, for example, by cooperation between hardware including circuits and image generation software.

[0048] The image generating unit 220 is configured to perform a process of generating an OCT intensity image that represents the intensity of the interference signal as visual information, and a process of generating a phase image that represents the phase information of the interference signal as visual information. A non-limiting example of the process of generating the intensity image will be described below. A non-limiting example of the process of generating the phase image will be described later, along with a description of the theoretical aspects of OCT blood flow measurement.

[0049] The image generator 220 generates an intensity image based on the data (interference signal) acquired by the spectrometer 130. Similar to conventional spectral-domain OCT, this intensity image generation process includes signal processing such as A / D conversion, denoising, filtering, and fast Fourier transform (FFT). The fast Fourier transform converts the interference signal acquired by the spectrometer 130 into an A-line profile (a reflection intensity profile along the z-direction). The A-line profile is visualized by applying imaging processing (a process of assigning pixel values ​​to reflection intensity values) to the A-line profile. This results in A-scan image data. By arranging multiple A-scan images according to a scan pattern, a cross-sectional image (e.g., B-scan image data, circle scan image data, etc.) corresponding to the scan pattern is constructed. When another OCT method is used, the cross-sectional image generator 221 performs known processing appropriate to the type of OCT method.

[0050] In some embodiments, the intensity image may be a dataset including a group of A-scan image data obtained by visualizing the reflection intensity profile of multiple A-lines arranged in the area where the OCT scan was performed. In other words, in some embodiments, the intensity image may be a dataset including a group of A-scan image data and their position information (coordinates). In another embodiment, the intensity image may be stack data constructed by embedding multiple B-scan images in a single three-dimensional coordinate system, i.e., a dataset including multiple B-scan images and their position information. In yet another embodiment, the intensity image may be volume data (voxel data) generated by applying a voxelization process to the stack data. Stack data and volume data are non-limiting examples of three-dimensional image data in which pixel coordinates are defined using a three-dimensional coordinate system. The process of generating the three-dimensional image data is performed by the image generation unit 220.

[0051] The image generation unit 220 can process the three-dimensional image data. For example, the image generation unit 220 can generate new image data by applying rendering to the three-dimensional image data. Rendering techniques include volume rendering, surface rendering, multiplanar reconstruction (MPR), maximum intensity projection (MIP), minimum intensity projection (MinIP), and average intensity projection (AIP). The image generation unit 220 can construct projection data by integrating (projecting) the three-dimensional image data in the z direction. The image generation unit 220 can construct a shadowgram by integrating (projecting) a portion of the three-dimensional image data (three-dimensional partial image data) in the z direction. The three-dimensional partial image data is extracted from the three-dimensional image data using any image segmentation method.

[0052] The ophthalmologic apparatus 1 can apply OCT blood flow measurement to the fundus Ef. The theoretical aspects of OCT blood flow measurement will be described below, as well as some non-limiting aspects of OCT blood flow measurement.

[0053] In a non-limiting aspect, blood flow measurement applies two types of scans (main scan and supplemental scan) to the fundus Ef. In the main scan, a region of interest (cross section of interest) that intersects with a blood vessel of interest in the fundus Ef at a position of interest is repeatedly scanned with the measurement light LS to acquire phase image data. On the other hand, in the supplemental scan, a predetermined cross section (supplemental cross section) is scanned with the measurement light LS to estimate the inclination of the blood vessel of interest in the cross section of interest. In a non-limiting aspect, the supplemental cross section may be, for example, a cross section (first supplemental cross section) that intersects with the blood vessel of interest and is located near the cross section of interest. In another non-limiting aspect, the supplemental cross section may be a cross section (second supplemental cross section) that intersects with the cross section of interest and is aligned with the blood vessel of interest. The inclination of the blood vessel of interest is the angle between the measurement light LS projected onto the cross section of interest and the blood vessel of interest, which is the Doppler angle in Doppler OCT.

[0054] An example of the application of the first supplemental cross section is shown in FIG. 5A. In this example, as shown in a fundus image D, one cross section of interest C0 located near the optic disc Da of the fundus oculi Ef and two supplemental cross sections C1 and C2 located nearby are set to intersect with a blood vessel of interest Db. One of the two supplemental cross sections C1 and C2 is located upstream of the blood vessel of interest Db relative to the cross section of interest C0, and the other is located downstream. The cross section of interest C0 and the supplemental cross sections C1 and C2 are oriented, for example, approximately perpendicular to the running direction of the blood vessel of interest Db.

[0055] An example of a case where the second supplemental cross section is applied is shown in FIG. 5B. In this example, a cross section of interest C0 similar to the example shown in FIG. 5A is set so as to be approximately perpendicular to the blood vessel of interest Db, and a supplemental cross section Cp is set so as to be approximately perpendicular to the cross section of interest C0. The supplemental cross section Cp is set along the blood vessel of interest Db. As an example, the supplemental cross section Cp may be set so as to pass through the central axis of the blood vessel of interest Db at the position of the cross section of interest C0.

[0056] It is desirable that the main scan in OCT blood flow measurement collects data over a period including at least one cardiac cycle of the subject's heart. This makes it possible to determine the hemodynamics of blood flow in all cardiac phases. The time period for performing the main scan may be a fixed time set in advance, or may be a time set for each subject or each examination. This fixed time period has conventionally been set to a time (e.g., 2 seconds) that is sufficiently longer than a standard cardiac cycle.

[0057] The image generating unit 220 includes a cross-sectional image generating unit 221 and a phase image generating unit 222. The cross-sectional image generating unit 221 includes a processor, and its functions are realized, for example, by cooperation between hardware including a circuit and cross-sectional image generating software. The phase image generating unit 222 includes a processor, and its functions are realized, for example, by cooperation between hardware including a circuit and phase image generating software.

[0058] The cross-sectional image generating unit 221 generates an intensity image based on data collected by an OCT scan of the fundus oculi Ef. The intensity image generating process may be the same as a conventional image generating method in the spectral domain OCT method.

[0059] The cross-sectional image generating unit 221 generates cross-sectional images (main cross-sectional images) representing time-series changes in the morphology of the cross-section of interest based on interference signals obtained by the spectroscope 130 during main scanning of the cross-section of interest of the fundus oculi Ef. As described above, during main scanning, the ophthalmologic apparatus 1 applies repeated scans to the cross-section of interest C0. These repeated scans include multiple B-scans for the cross-section of interest C0. The interference signals sequentially generated by the spectroscope 130 in the multiple B-scans are sequentially input to the cross-sectional image generating unit 221. The cross-sectional image generating unit 221 generates one main cross-sectional image corresponding to the cross-section of interest C0 based on the interference signals corresponding to each B-scan. The cross-sectional image generating unit 221 repeats this process the number of times the B-scan is repeated during main scanning, thereby generating a series of main cross-sectional images in time series. In this way, the cross-sectional image generating unit 221 generates multiple intensity images corresponding to the multiple B-scans based on the data set collected by the repeated scanning of the main scanning. In some exemplary embodiments, the image quality of the main cross-sectional images can be improved by dividing a series of main cross-sectional images obtained by main scanning into multiple groups, and applying image synthesis (e.g., averaging) to the main cross-sectional images included in each group to generate multiple composite images.

[0060] The cross-sectional image generating unit 221 generates a cross-sectional image (supplementary cross-sectional image) representing the morphology of the supplementary cross-section based on an interference signal obtained by the spectroscope 130 during supplementary scanning of the supplementary cross-section of the fundus oculi Ef. The process of generating the supplementary cross-sectional image is performed in the same manner as the process of generating the main cross-sectional image. The supplementary cross-sectional image may be one cross-sectional image or two or more cross-sectional images. In some exemplary embodiments, the image quality of the supplementary cross-sectional image can be improved by scanning the supplementary cross-section multiple times to generate multiple cross-sectional images and applying image synthesis to these cross-sectional images to generate a synthesized image. When the supplementary cross-sections C1 and C2 illustrated in FIG. 5A are applied, the cross-sectional image generating unit 221 generates a supplementary cross-sectional image corresponding to the supplementary cross-section C1 and a supplementary cross-sectional image corresponding to the supplementary cross-section C2. When the supplementary cross-section Cp illustrated in FIG. 5B is applied, the cross-sectional image generating unit 221 generates a supplementary cross-sectional image corresponding to the supplementary cross-section Cp.

[0061] The phase image generating unit 222 generates a phase image representing a time-series change in the phase difference in the cross section of interest based on the interference signal obtained by the spectroscope 130 during the main scan. The interference signal used to generate the phase image may be the same as the interference signal used to generate the principal cross section image by the cross section image generating unit 221. In this case, a natural positional correspondence is defined between the pixels of the principal cross section image and the pixels of the phase image, making it easy to align the principal cross section image and the phase image. In contrast, in some embodiments, the principal cross section image and the phase image may be generated from different interference signals. In this case, for example, a known image registration method can be used to align the principal cross section image and the phase image.

[0062] A non-limiting example of a process for generating a phase image will now be described. The phase image in this example is obtained by calculating the phase difference between adjacent A-line complex signals (i.e., signals corresponding to adjacent scanning points). In other words, the phase image in this example is generated based on the time-series changes in pixel values ​​(brightness values) of the principal cross-sectional image. For any pixel in the principal cross-sectional image, the phase image generating unit 222 creates a graph showing the time-series changes in the brightness value of that pixel. The phase image generating unit 222 calculates the phase difference Δφ between two time points t1 and t2 (t2 = t1 + Δt) that are separated by a predetermined time interval Δt in this graph. This phase difference Δφ is then defined as the phase difference Δφ(t1) at time point t1 (or more generally, any time point between time points t1 and t2). By performing this series of processes for each of a number of preset time points, the time-series changes in the phase difference at that pixel can be obtained. Note that the time-series changes in the phase difference can be obtained by making the time interval Δt sufficiently small to ensure phase correlation. For this reason, the scanning (main scanning) of the measuring light LS executes oversampling in which the time interval Δt is set to a value smaller than the time corresponding to the resolution of the cross-sectional image.

[0063] A phase image may be image data obtained by expressing the phase difference value of each pixel at each time point. For example, a phase image is an image obtained by expressing the phase difference value of each pixel at each time point as visual information (imaging process). This imaging process includes, for example, a process of expressing the phase difference value using predetermined display parameters (e.g., display color, brightness, etc.). Some imaging processes can use different display colors to indicate an increase in phase over time and a decrease in phase over time. For example, an increase in phase over time can be expressed in red, and a decrease in phase over time can be expressed in blue. Furthermore, some imaging processes can express the magnitude of phase change (phase change amount) as the density of the display color. Some imaging processes described herein enable visualization of the direction and magnitude of blood flow. A phase image is generated by performing such imaging process on each pixel.

[0064] The data processing unit 230 includes, as exemplary elements for obtaining hemodynamic information, a vascular region specifying unit 231 and a hemodynamic information generating unit 232. The hemodynamic information generating unit 232 may include a Doppler angle calculating unit 233, a blood flow velocity calculating unit 234, a vascular diameter calculating unit 235, and a blood flow amount calculating unit 236.

[0065] The vascular region specifying unit 231 includes, for example, a processor operable according to a vascular region specifying program. The hemodynamic information generating unit 232 includes, for example, a processor operable according to a hemodynamic information generating program. The Doppler angle calculating unit 233 includes, for example, a processor operable according to a Doppler angle calculation program. The blood flow velocity calculating unit 234 includes, for example, a processor operable according to a blood flow velocity calculation program. The blood vessel diameter calculating unit 235 includes, for example, a processor operable according to a blood vessel diameter calculation program. The blood flow volume calculating unit 236 includes, for example, a processor operable according to a blood flow volume calculation program.

[0066] The vascular region identifying unit 231 analyzes an OCT image of the fundus and identifies an image region (vascular region) corresponding to a blood vessel in the OCT image. The vascular region identifying unit 231 also analyzes a front image of the fundus (e.g., an observed image or a photographed image acquired by the fundus camera unit 2) and identifies an image region (vascular region) corresponding to a blood vessel in the front image. The vascular region identifying process performed by the vascular region identifying unit 231 may be image processing using any image segmentation, and is performed, for example, by analyzing pixel values ​​in the target image (e.g., threshold processing). In some embodiments, the vascular region identifying unit 231 identifies a vascular region corresponding to the blood vessel of interest Db from each of the principal cross-sectional image, the supplementary cross-sectional image, and the phase image.

[0067] In some cases, the principal and supplementary cross-sectional images have sufficient resolution to be analyzed in the vascular region identification process, while the phase images do not have sufficient resolution to identify the boundaries of the vascular regions. Even in such cases, since hemodynamic information is generated based on the phase images, it is necessary to identify the vascular regions in the phase images with high accuracy. For this purpose, for example, the following process can be adopted.

[0068] When the principal cross-sectional image and the phase image are generated based on the same interference signal, the natural positional correspondence relationship (described above) defined between the pixels of the principal cross-sectional image and the pixels of the phase image can be utilized. For example, the vascular region identifying unit 231 can perform a process of analyzing the principal cross-sectional image to identify a vascular region and a process of identifying an image region in the phase image corresponding to the vascular region in the principal cross-sectional image based on the positional correspondence relationship. The image region in the phase image is adopted as the vascular region in the phase image. This allows the vascular region in the phase image to be determined with high accuracy. When the principal cross-sectional image and the phase image are generated based on mutually different interference signals, the vascular region in the phase image can be determined by utilizing the result of image registration (described above) between the principal cross-sectional image and the phase image instead of the natural positional correspondence relationship.

[0069] The hemodynamic information generating unit 232 generates information indicating the hemodynamics of the blood flow in the fundus blood vessels (hemodynamic information). The hemodynamic information may be information on any parameter (hemodynamic parameter) indicating the fundus hemodynamics. Although the present disclosure describes blood velocity and blood volume, the hemodynamic parameters are not limited to these.

[0070] The hemodynamic information generator 232 generates hemodynamic information regarding the interested blood vessel Db. As described above, the hemodynamic information generator 232 in some embodiments includes a Doppler angle calculator 233, a blood flow velocity calculator 234, a blood vessel diameter calculator 235, and a blood flow amount calculator 236.

[0071] The Doppler angle calculation unit 233 calculates an estimated value of the tilt of the blood vessel of interest based on data of the supplementary cross section (cross-sectional data, supplementary cross-sectional image) collected by the supplementary scan. The calculated value may be, for example, a value based on a measurement value of the tilt of the blood vessel of interest on the cross section of interest, or an approximate value thereof. As described above, the tilt of the blood vessel of interest is a parameter equivalent to the Doppler angle in Doppler OCT. That is, the Doppler angle is the angle between the incident direction of the measurement light LS in the main scan on the cross section of interest and the direction of the axis of the blood vessel of interest (i.e., the tilt of the blood vessel of interest), and therefore the tilt of the blood vessel of interest is equivalent to the Doppler angle.

[0072] An example of actually measuring the gradient value of the blood vessel of interest will be described (first example of gradient estimation). When the supplementary cross sections C1 and C2 shown in Fig. 5A are applied, the Doppler angle calculation unit 233 can calculate the gradient of the blood vessel of interest Db on the cross section of interest C0 based on the positional relationship between the cross section of interest C0, the supplementary cross sections C1, and the supplementary cross sections C2, and the vascular region identification result obtained by the vascular region identification unit 231.

[0073] A method for calculating the gradient of the blood vessel of interest Db will be described with reference to FIG. 6A . The symbols G0, G1, and G2 respectively denote the principal cross-sectional image at the cross-section of interest C0, the supplementary cross-section image at the supplementary cross-section C1, and the supplementary cross-section image at the supplementary cross-section C2. The symbols V0, V1, and V2 respectively denote the vascular region in the principal cross-sectional image G0, the vascular region in the supplementary cross-section image G1, and the vascular region in the supplementary cross-section image G2. The z-coordinate axis shown in FIG. 6A substantially coincides with the incident direction of the measurement light LS. The distance between the principal cross-sectional image G0 (cross-section of interest C0) and the supplementary cross-sectional image G1 (supplementary cross-section C1) is denoted by d, and the distance between the principal cross-sectional image G0 (cross-section of interest C0) and the supplementary cross-sectional image G2 (supplementary cross-section C2) is also denoted by d. The distance between adjacent cross-sectional images, i.e., the distance between adjacent cross-sections, is called the inter-section distance.

[0074] The Doppler angle calculation unit 233 can calculate the gradient A of the blood vessel of interest Db in the cross section of interest C0 based on the positional relationship between the three vascular regions V0, V1, and V2. This positional relationship can be determined, for example, by connecting the three vascular regions V0, V1, and V2. As a specific example, the Doppler angle calculation unit 233 can identify the characteristic positions of each of the three vascular regions V0, V1, and V2 and connect these characteristic positions. This characteristic position may be, for example, one of the center position, the center of gravity position, the top (the position with the smallest z-coordinate value), and the bottom (the position with the largest z-coordinate value). The characteristic positions may be connected by any method, such as connecting them with a line segment or an approximation curve (such as a spline curve or a Bezier curve).

[0075] Furthermore, the Doppler angle calculation unit 233 calculates the gradient A of the blood vessel of interest Db in the cross section of interest C0 based on a connecting line connecting the characteristic positions identified from the three vascular regions V0, V1, and V2. If the connecting line is a line segment, the Doppler angle calculation unit 233 can calculate the gradient A based on the gradient of a first line segment connecting the characteristic position of the cross section of interest C0 to the characteristic position of the supplementary cross section C1 and the gradient of a second line segment connecting the characteristic position of the cross section of interest C0 to the characteristic position of the supplementary cross section C2. A non-limiting example of this calculation process may be calculating the average gradient of the two line segments. If the connecting line is an approximated curve, the Doppler angle calculation unit 233 can calculate the gradient A as the gradient of the approximated curve at the position where the approximated curve intersects with the cross section of interest C0. In the Doppler angle calculation process, the inter-section distance d is used, for example, when embedding the cross-sectional images G0 to G2 in an xyz coordinate system to calculate the connecting line.

[0076] In the above example, the vascular region in three cross sections is considered. In some embodiments, the gradient may be calculated by considering two cross sections. As a non-limiting example, the gradient A of the blood vessel Db of interest in the cross section C0 of interest may be calculated as the gradient of the first line segment or the gradient of the second line segment. Alternatively, the gradient A of the blood vessel Db of interest in the cross section C0 of interest may be calculated based on two supplementary cross-sectional images G1 and G2.

[0077] An example of calculating an approximate value of the gradient of the blood vessel of interest (second example of gradient estimation) will be described below. When the supplementary cross section Cp shown in FIG. 5B is applied, the Doppler angle calculation unit 233 can analyze the supplementary cross section image corresponding to the supplementary cross section Cp to calculate an approximate value of the gradient of the blood vessel of interest Db on the cross section C0 of interest.

[0078] A method for approximating the gradient of the blood vessel of interest Db will be described with reference to Fig. 6B. The symbol Gp denotes a supplemental cross-sectional image at the supplemental cross-section Cp. The symbol A denotes the gradient of the blood vessel of interest Db at the cross-section of interest C0, similar to the example shown in Fig. 6A.

[0079] In this example, the Doppler angle calculation unit 233 can analyze the supplemental cross-sectional image Gp to identify an image region corresponding to a predetermined tissue of the fundus oculi Ef. For example, the Doppler angle calculation unit 233 can identify an image region (internal limiting membrane region) M corresponding to the internal limiting membrane (ILM), which is a superficial tissue of the retina. To identify the image region, for example, a known image segmentation method is used.

[0080] It is known that the internal limiting membrane and the fundus blood vessels are approximately parallel to each other. The Doppler angle calculation unit 233 calculates the gradient A of the internal limiting membrane region M on the cross section C0 of interest. ａｐｐ The gradient A of the inner limiting membrane region M in the cross section C0 of interest is calculated. ａｐｐ is used as an approximation of the gradient A of the blood vessel Db of interest in the cross section C0 of interest.

[0081] 6A and 6B is a vector representing the direction of the blood vessel of interest Db, and its value may be defined arbitrarily. In some non-limiting examples, the value of the gradient A can be defined as the angle (Doppler angle) formed by the gradient (vector) A and the z-axis. Similarly, the gradient A shown in FIG. ａｐｐ is a vector representing the direction of the inner limiting membrane region M, and its value may be defined arbitrarily. For example, the gradient (vector) A ａｐｐ The angle between the z-axis and the Doppler angle is the gradient A. ａｐｐ Here, the orientation of the z-axis substantially coincides with the incident direction of the measurement light LS.

[0082] As a third example of estimating the gradient of the blood vessel of interest, the Doppler angle calculation unit 233 can analyze the supplementary cross-sectional image Gp shown in FIG. 6B to identify an image region corresponding to the blood vessel of interest Db and determine the gradient of the image region at a position corresponding to the cross section of interest C0. In this case, the Doppler angle calculation unit 233 can, for example, perform a curve approximation on the boundary or central axis of the image region corresponding to the blood vessel of interest Db and determine the gradient of the approximated curve at a position corresponding to the cross section of interest C0. It is also possible to apply a similar curve approximation to an image region corresponding to a specific tissue of the fundus oculi Ef described above (for example, the internal limiting membrane region M).

[0083] The processing performed by the Doppler angle calculation unit 233 is not limited to the above example, and may be any processing that can obtain an estimated value of the inclination of the blood vessel Db of interest (e.g., the inclination value of the blood vessel Db itself, its approximate value, etc.) based on cross-sectional data collected by applying an OCT scan to a cross section of the fundus Ef.

[0084] The blood flow velocity calculation unit 234 calculates the blood flow velocity of blood flowing through the blood vessel Db at the cross section C0 of interest based on information on the time-series change in phase difference obtained as a phase image. The calculated information may be the value of the blood flow velocity at a specific time point (blood flow velocity value) or the time-series change in the blood flow velocity value (blood flow velocity change information). The blood flow velocity value may be a value at a specific cardiac phase selected from the cardiac cycle (e.g., the R-wave phase). The period for which the blood flow velocity change information is defined may be the entire period during which the main scan is applied to the cross section C0 of interest, or may be a selected portion of that period.

[0085] When the blood flow velocity change information is obtained, the blood flow velocity calculation unit 234 may calculate a statistical value of the blood flow velocity during the measurement period. This statistical value may be, for example, any of the mean value, standard deviation, variance, median, mode, maximum value, minimum value, local maximum value, and local minimum value. However, it is not limited to these. Furthermore, when the blood flow velocity change information is obtained, the change in the blood flow velocity can be visualized to generate visual information (e.g., a graph, a histogram, etc.).

[0086] The blood flow velocity calculation unit 234 calculates the blood flow velocity using the Doppler OCT technique. At this time, the gradient A (or its approximate value A) of the blood vessel Db of interest in the cross section C0 calculated by the Doppler angle calculation unit 233 is used. ａｐｐ Specifically, the blood flow velocity calculation unit 234 can use the following formula: Δf=[2nv cos θ] / λ.

[0087] Here, Δf indicates the Doppler shift experienced by the scattered light of the measurement light LS; n indicates the refractive index of the medium; v indicates the flow velocity (blood flow velocity) of the medium; θ indicates the angle between the incident direction of the measurement light LS and the flow vector of the medium; and λ indicates the central wavelength of the measurement light LS.

[0088] In some embodiments, n and λ are known, Δf is obtained from the time series of the phase difference, and θ is the Doppler angle (slope A or approximate value A ａｐｐ The blood flow velocity calculation unit 234 calculates the blood flow velocity v by substituting the medium refractive index n, the central wavelength λ of the measurement light LS, the Doppler shift Δf, and the Doppler angle θ into the above equation: v = [λΔf] / [2n cos θ]. Note that the method for calculating the blood flow velocity is not limited to the method described here, and any method that can be employed in Doppler OCT may be used.

[0089] The blood vessel diameter calculation unit 235 calculates the diameter of the blood vessel Db of interest in the cross section C0 of interest. Examples of this calculation method include a first calculation method using a frontal fundus image and a second calculation method using a cross section image.

[0090] When the first calculation method is applied, an image of the area of ​​the fundus Ef including the position of the cross section of interest C0 is captured in advance. The resulting frontal fundus image may be, for example, a frame of an observed image, a captured image (color image, fluorescent contrast image), or an OCT angiography image (motion contrast image).

[0091] The blood vessel diameter calculation unit 235 sets the scale of the front fundus image based on various factors that determine the relationship between the scale in the image and the scale in real space, such as the imaging angle of view (imaging magnification, scan dimension), working distance, information on the ocular optical system, etc. This scale, for example, corresponds the interval between adjacent pixels (pixel pitch) to the scale in real space (e.g., pixel pitch = 10 micrometers). The blood vessel diameter calculation unit 235 can calculate the diameter of the blood vessel Db of interest in the cross section C0 of interest, i.e., the diameter of the blood vessel region V0, based on the scale set for the front fundus image and the pixels in the blood vessel region V0.

[0092] The second calculation method will be described. In the second calculation method, a cross-sectional image of the cross-section of interest C0 is typically used. This cross-sectional image may be a principal cross-sectional image or another cross-sectional image. The scale of the cross-sectional image is determined based on the measurement conditions of the OCT, etc. In some embodiments, the cross-section of interest C0 is scanned as shown in FIG. 5A or 5B. The length of the cross-section of interest C0 is determined based on various factors that determine the relationship between the scale on the image and the scale in real space, such as the scan dimension, working distance, and information about the ocular optical system. The blood vessel diameter calculation unit 235 can calculate the diameter of the blood vessel of interest Db in the cross-section of interest C0 by performing a process of calculating the pixel pitch based on the length of the cross-section of interest C0 and a process similar to that of the first calculation method.

[0093] The blood flow rate calculation unit 236 calculates the blood flow rate in the blood vessel of interest Db based on the blood flow velocity calculated by the blood flow velocity calculation unit 234 and the blood vessel diameter calculated by the blood vessel diameter calculation unit 235. An example of this process will be described below. It is assumed that the blood flow in the blood vessel is a Hagen-Poiseuille flow. Furthermore, the blood vessel diameter is represented by w, and the maximum value of the blood flow velocity is represented by Vm. In this case, the blood flow rate Q is expressed by the following equation: Q = [πw ２ Vm] / 8.

[0094] The blood flow calculation unit 236 calculates the blood flow Q by substituting the blood vessel diameter value w calculated by the blood vessel diameter calculation unit 235 and the maximum value Vm based on the blood flow velocity value calculated by the blood flow velocity calculation unit 234 into this formula.

[0095] The types of parameters calculated by the hemodynamic information generating unit 232 are not limited to the several parameters described above. For example, the hemodynamic information generating unit 232 can calculate parameters obtained by relative measurement in addition to or instead of parameters obtained by absolute measurement, such as blood flow velocity and blood flow rate. Some non-limiting examples of hemodynamic parameters that can be used in this embodiment will be described below.

[0096] Even when an inaccurate Doppler angle value is obtained, it is possible to extract and analyze a profile from an image showing the inside of a blood vessel, or to extract the shape of a pulse wave curve (a waveform derived from the heartbeat) from the time course of an image showing the inside of a blood vessel. Several studies have demonstrated the usefulness of the relative values ​​obtained in this way. It is also possible to extract specific characteristic parameters from the waveform of a pulse wave curve. The extracted characteristic parameters can be used for hemodynamic evaluation, disease assessment, etc.

[0097] The flow of blood within a blood vessel can be considered essentially laminar, with the flow velocity decreasing as the blood approaches the vessel wall due to the frictional drag from the vessel wall, and reaching its maximum at the center of the vessel. Laminar flow is a parabolic flow, and the diastolic and systolic waveforms in the cardiac cycle can be read from the pulse wave. Therefore, the characteristics of these waveforms can be determined. For example, parameters relating to deviations from a specific waveform (such as the presence, degree, and frequency of deviations) can be determined.

[0098] The blood flow velocity in veins is not always constant, but exhibits slight variations (pulsations). Parameters that indicate these minute pulsations (absolute velocity parameters, relative velocity parameters, etc.) can be calculated.

[0099] <Non-limiting aspects of the ophthalmic device> Several non-limiting aspects realized by applying the ophthalmic device 1 having the hardware aspects, software aspects, and functional aspects described above will be described. In the following description, matters related to the ophthalmic device 1 will be referenced and used as appropriate. Any matter related to the ophthalmic device 1 can be at least partially combined with each aspect. Two or more aspects can be at least partially combined.

[0100] 7 shows the configuration of an ophthalmic apparatus 1000 according to one non-limiting embodiment. The ophthalmic apparatus 1000 performs OCT blood flow measurement to measure the blood flow dynamics in the blood vessels at the fundus of the eye. The ophthalmic apparatus 1000 includes a scanning unit 1010, a scan control unit 1020, a phase image generating unit 1030, a vascular region specifying unit 1040, a future time point estimating unit 1050, a Doppler angle calculating unit 1070, a blood flow dynamics information generating unit 1080, a blood vessel of interest specifying unit 1090, and an alignment unit 1100.

[0101] The scan unit 1010 is configured to collect data by applying an OCT scan to the fundus Ef of the subject's eye E. In a preparatory stage for OCT blood flow measurement, the scan unit 1010 applies repeated scans to a specific blood vessel (blood vessel of interest) in the fundus Ef. The repeated scans in the preparatory stage collect data by applying multiple scans to a specific cross section (cross section of interest) in the blood vessel of interest. The blood vessel of interest to which the repeated scans in the preparatory stage are applied may be the same blood vessel as the blood vessel of interest to which OCT blood flow measurement is applied, or may be a different blood vessel. Furthermore, the cross section of interest to which the repeated scans in the preparatory stage are applied may be the same cross section as the cross section of interest to which OCT blood flow measurement is applied, or may be a different cross section.

[0102] Furthermore, the scanning unit 1010 applies scans for OCT blood flow measurement (e.g., the above-mentioned main scan and supplementary scan) to the blood vessel of interest to collect data. However, the types of scans that the scanning unit 1010 can perform are not limited to these. The ophthalmologic apparatus 1 of a non-limiting embodiment can achieve the functions of the scanning unit 1010 using the fundus camera unit 2 and the OCT unit 100.

[0103] The blood vessel of interest (at least one of the blood vessel of interest to which the preparatory scan is applied and the blood vessel of interest to which OCT blood flow measurement is applied) is designated in advance. The designation of the blood vessel of interest is performed automatically or manually. Automatic designation is performed by a blood vessel of interest designation unit 1090 described below. Manual designation is performed by a combination of displaying an image of the fundus oculi Ef using a user interface (the above-mentioned user interface 240) and performing a position designation operation on this displayed image. The same applies to designation of the cross section of interest.

[0104] The scan control unit 1020 is configured to control the scan unit 1010. For example, the scan control unit 1020 can cause the scan unit 1010 to execute the above-mentioned repetitive scan in the preparation stage for OCT blood flow measurement. The scan control unit 1020 can also cause the scan unit 1010 to execute scans (main scans and supplementary scans) for OCT blood flow measurement.

[0105] The scan control unit 1020 is realized by cooperation between hardware including a circuit and scan control software. The scan control unit 1020 has a timing function. The ophthalmologic apparatus 1 of a non-limiting embodiment can realize the functions of the scan control unit 1020 using the control unit 210 (main control unit 211).

[0106] The phase image generating unit 1030 processes data collected by repeated scans performed by the scanning unit 1010 in preparation for OCT blood flow measurement to generate a phase image. As described above, a phase image is data representing time-series changes in phase difference at each pixel. For details about the phase image and its generation method, please refer to the above description of the phase image generating unit 222.

[0107] The phase image generating unit 1030 is realized by cooperation between hardware including a circuit and phase image generating software. The ophthalmologic apparatus 1 of a non-limiting embodiment can realize the function of the phase image generating unit 1030 by using the phase image generating unit 222.

[0108] The vascular region identifying unit 1040 is configured to identify a vascular region in the phase image generated by the phase image generating unit 1030. A phase image is data that represents a time-series change in phase difference at each pixel. In other words, a phase image is a time-series image including a plurality of frames. The value of each pixel in each frame is the value of the phase difference at the time of the frame. The vascular region identifying unit 1040 identifies a vascular region from each frame. Therefore, the vascular region identified from the phase image by the vascular region identifying unit 1040 is an image that represents a time-series change in the phase difference value.

[0109] In some embodiments, the vascular region identifying unit 1040 applies image analysis to each of the multiple frames forming the phase image, thereby identifying multiple vascular regions (multiple groups of vascular regions) corresponding to each of the multiple frames.

[0110] In some embodiments, the vascular region identification unit 1040 identifies a vascular region from a first group of frames (one or more frames) among a plurality of frames forming a phase image, and identifies a vascular region in a second group of frames (a group consisting of frames other than the first group of frames) based on the vascular region identified from the first group of frames.

[0111] The image analysis method for detecting a vascular region from a phase image (frame) may be any method. For example, the image analysis may include any image segmentation. The image segmentation may be either an image segmentation method using a machine learning algorithm (machine learning model) or an image segmentation method using a non-machine learning algorithm, or may be at least a partial combination of both.

[0112] Non-limiting examples of image segmentation methods applicable to the vascular region identification unit 1040 include thresholding-based methods, edge detection-based methods, region-based methods, clustering-based methods, convolutional neural network (CNN)-based methods, transformer-based methods, generative adversarial network (GAN)-based methods, self-supervised learning (SSL)-based methods, graph-based methods, etc. The image segmentation performed by the vascular region identification unit 1040 may be a combination of two or more methods.

[0113] In some embodiments, the vascular region identifying unit 1040 applies image analysis for identifying a vascular region directly to the phase image generated by the phase image generating unit 1030. That is, in some embodiments, the vascular region identifying unit 1040 identifies a vascular region from the phase image without processing a separate image.

[0114] In contrast, the vascular region identifying unit 1040 in some embodiments identifies a vascular region from a phase image by using an image other than the phase image. The other image may depict the fundus tissue in more detail than the phase image, and may be, for example, an OCT intensity image (cross-sectional image, B-scan image). The cross-sectional image may be an intensity image of a cross-section of interest or an intensity image of a cross-section located near the cross-section of interest. The number of cross-sectional images used may be one or two or more.

[0115] When two or more cross-sectional images are used, a cross-sectional image generating unit (not shown in FIG. 7 , corresponding to the cross-sectional image generating unit 221 described above) generates multiple cross-sectional images corresponding to the multiple scans in the repeated scans performed by the scanning unit 1010. The vascular region identifying unit 1040 combines the multiple cross-sectional images to generate a composite cross-sectional image. This image combination is, for example, an arithmetic average, which reduces random noise such as speckle noise. The vascular region identifying unit 1040 identifies the vascular region by applying image analysis to the composite cross-sectional image. Because the multiple cross-sectional images and the phase image are derived from the same acquired data, there is a natural positional correspondence between the pixels of the composite cross-sectional image and the pixels of the phase image. Based on this positional correspondence, the vascular region identifying unit 1040 identifies the vascular region in the phase image corresponding to the vascular region in the composite cross-sectional image. Note that the vascular region identifying process using a single cross-sectional image is performed in the same manner as when two or more cross-sectional images are used, except that the composite cross-sectional image is generated and analyzed.

[0116] The vascular region specifying unit 1040 is realized by cooperation between hardware including a circuit and vascular region specifying software. The ophthalmologic apparatus 1 of a non-limiting embodiment can realize the function of the vascular region specifying unit 1040 by using the data processing unit 230 (vascular region specifying unit 231).

[0117] The future time point estimation unit 1050 applies time series analysis to the vascular region identified from the phase image by the vascular region identification unit 1040, and estimates a future time point corresponding to a predetermined cardiac phase.

[0118] Time series analysis is generally a technique for analyzing phenomena that vary over time, and more specifically, a technique for predicting the future based on the periodicity and trend of data observed at regular time intervals. As described above, a vascular region in a phase image is an image that represents time-series changes in phase difference values. The future time estimation unit 1050 estimates a future time corresponding to a predetermined cardiac phase by applying time series analysis, which analyzes the phase difference values ​​that vary over time, to the vascular region. More specifically, the future time estimation unit 1050 estimates a future time corresponding to a predetermined cardiac phase by determining the periodicity and trend of the phase difference values ​​observed at regular time intervals as the vascular region in the phase image.

[0119] The predetermined cardiac phase is a predetermined phase in the cardiac cycle, and in particular, a phase corresponding to the timing at which repeated scans (main scans) are started in OCT blood flow measurement. The cardiac phase considered by the future time estimator 1050 of this embodiment may be, for example, the point at which the cardiac cycle transitions from diastole to systole. This point is referred to as the start point of systole. The start point of systole may be the actual point at which the cardiac cycle transitions from diastole to systole, or may be a point at which an allowable time difference is added (referred to as a nearby point). The time difference of the nearby point may be an error associated with measurement or analysis, or may be an intentionally set time difference. In this way, the future time estimator 1050 of this embodiment determines a future time (estimated value) corresponding to the start point of systole in the cardiac cycle. This future time may be the start point of systole that arrives immediately after the current time, or a subsequent start point of systole. Furthermore, the future time point estimation unit 1050 of this aspect may determine one future time point or may determine multiple future time points. When multiple future time points are determined, the time difference between any two of those future time points is an integer multiple of the cardiac cycle.

[0120] In some embodiments, the future time point estimation unit 1050 obtains a cardiac cycle by applying time series analysis to the vascular region identified from the phase image by the vascular region identification unit 1040. The time series changes in the phase difference values ​​in the vascular region are caused by the heartbeat and are therefore periodic. The time series analysis of this embodiment obtains the period of the time series changes in the phase difference values ​​(time series changes in pixel values ​​obtained by visualizing the phase difference values).

[0121] In some embodiments, the future time estimation unit 1050 applies time series analysis to the vascular region identified from the phase image by the vascular region identification unit 1040 to determine the cardiac cycle and a past time point corresponding to the predetermined cardiac phase (the start time of systole). This past time point may be the start time of systole immediately preceding the current time point, or may be an earlier start time of systole. Furthermore, the future time estimation unit 1050 of this embodiment may determine one past time point or multiple past time points. When multiple past time points are determined, the time difference between any two of these past time points is an integer multiple of the cardiac cycle. Furthermore, the future time estimation unit 1050 of this embodiment estimates a future time point corresponding to the start time of systole based on the cardiac cycle and the past time point determined by the time series analysis. Two examples of the future time estimation process of this embodiment are described below. The processes in these examples are not limiting, and other processes that can be used to estimate future times may also be used.

[0122] 8 shows a schematic diagram of a heartbeat waveform. The horizontal axis represents time t, and the vertical axis represents blood flow velocity v. ０ indicates the current time point. For example, the future time point estimation unit 1050 applies the time series image to the phase image to estimate the current time point t ０ Two time points (two past time points) t that are earlier than the start time of the systole －１ and t －２ Furthermore, the future time estimation unit 1050 determines the time t －１ and t －２ This time interval represents the cardiac cycle T. The future time point estimation unit 1050 calculates the time interval between the current time point t ０ The previous time t just before －１By adding the cardiac cycle T to ０ The future time t that arrives immediately after １ The future time estimation unit 1050 calculates the current time t ０ The previous time t just before －１ By adding 2T, which is twice the cardiac cycle T, to １ The next future time t ２ Generally, the future time estimation unit 1050 calculates the current time t ０ The previous time t just before －１ By adding nT, which is n times the cardiac cycle T, to the current time, the nth future time t ｎ can be obtained (n is a positive integer).

[0123] In another example, the future time estimation unit 1050 applies a time series image to a phase image to estimate the current time t ０ In this example, a time point (a past time point) is identified that is earlier than the current time point t ０ The previous time t just before －１ The same applies when another past time point is specified. The future time point estimation unit 1050 also applies the time series image to the phase image to estimate the current time point t ０ In the example of FIG. 8, two time points corresponding to two peaks of the blood flow velocity (two past peak time points) are identified. Furthermore, the future time point estimation unit 1050 calculates the time interval between the identified two past peak time points. This time interval represents the cardiac cycle T. The future time point estimation unit 1050 calculates the time interval between the past time point t －１ By adding the cardiac cycle T to ０ The future time t that arrives immediately after １ Generally, the past time t －１ By adding nT, which is n times the cardiac cycle T, to the current time, the nth future time t ｎ can be obtained (n is a positive integer).

[0124] The future time estimation unit 1050 is realized by cooperation between hardware including a circuit and future time estimation software. The ophthalmologic apparatus 1 according to a non-limiting embodiment can realize the function of the future time estimation unit 1050 by using the data processing unit 230.

[0125] Information about the future time point determined by the future time point estimation unit 1050 is sent to the scan control unit 1020. The scan control unit 1020 controls the scan unit 1010 to apply a first scan to a first cross section of the blood vessel of interest to collect first data (first scan data 1061) before the future time point arrives. Furthermore, the scan control unit 1020 controls the scan unit 1010 to apply a second scan to a second cross section of the blood vessel of interest to collect second data (second scan data 1062) when the future time point arrives.

[0126] The first scan corresponds to a supplemental scan in OCT blood flow measurement of a blood vessel of interest. The first scan may be, for example, a B-scan of two or more cross sections (first cross sections) that traverse the blood vessel of interest (see FIGS. 5A and 6A ), or a B-scan of one or more cross sections (first cross sections) that longitudinally cut the blood vessel of interest (see FIGS. 5B and 6B ). The second scan corresponds to a main scan (repeated scan) in OCT blood flow measurement of a cross section (second cross section) of the blood vessel of interest.

[0127] As described above, in some aspects, the future time point estimation unit 1050 obtains the cardiac cycle by applying time series analysis to the vascular region in the phase image. In this aspect, the scan control unit 1020 can control the scan unit 1010 to start a second scan (main scan) at the future time point estimated by the future time point estimation unit 1050, and can also control the scan unit 1010 to end the second scan at a time point between when one cardiac cycle has elapsed and when two cardiac cycles have elapsed from this future time point.

[0128] Referring to the example of FIG. 8, the scan control unit 1020 of this embodiment performs the scan at a future time t １ The scan unit 1010 is controlled to start main scanning (repeated scanning) at a future time t １When one cardiac cycle T has elapsed since ２ and at the point t ３ The scanning unit 1010 is controlled so that the main scanning is completed at a time between the time when the scanning unit 1010 is stopped and the time when the main scanning is completed.

[0129] The length of time over which the main scan is performed in this embodiment is at least one cardiac cycle (T) and at most two cardiac cycles (2T). This length of time is shorter than the length of time in the past, in which the main scan was performed for a period (e.g., two seconds) that was significantly longer than a standard cardiac cycle. Moreover, since this embodiment collects data for at least one cardiac cycle, it is possible to determine the hemodynamics of blood flow in all cardiac phases.

[0130] In some embodiments, the scan control unit 1020 controls the scan unit 1010 to start a second scan (main scan) at the future time estimated by the future time estimation unit 1050, and controls the scan unit 1010 to end the second scan at a time when one cardiac cycle has elapsed from this future time.

[0131] Referring to the example of FIG. 8, the scan control unit 1020 of this embodiment performs the scan at a future time t １ The scan unit 1010 is controlled to start main scanning (repeated scanning) at a future time t １ When one cardiac cycle T has elapsed since ２ The scan unit 1010 is controlled to terminate the main scan at time T. The length of time for which the main scan is performed in this mode is one cardiac cycle (T), which is the shortest main scan execution time required to determine the hemodynamics in all cardiac time phases.

[0132] In some embodiments, the scan control unit 1020 controls the scan unit 1010 to start a first scan (supplementary scan) at a time point that is a predetermined time required for the first scan before the future time point estimated by the future time point estimation unit 1050, and also controls the scan unit 1010 to start a second scan (main scan) immediately after the end of the first scan (supplementary scan). The time required for the first scan (required time) is, for example, the time required to perform B-scans on one or more predetermined cross sections (control time, operation time, time lag, etc.), and is therefore a known value (referred to as a known time) that can be calculated in advance. Here, the known time may be set by taking into account the time required to transition from the first scan to the second scan. The start time of the first scan is set to a time that is the known time before the future time point estimated by the future time point estimation unit 1050. The first scan started at this set time is performed for the known time and completed almost simultaneously with the arrival of the future time estimated by the future time estimation unit 1050. The second scan is then started in response to the arrival of the future time. This second scan is performed for a predetermined period set, for example, between one cardiac cycle and two cardiac cycles.

[0133] 9 shows an example of the operation of this mode. The scan control unit 1020 of this example calculates the time of the future t １ (the start point of the systole) from the preset required time L of the first scan. １ The previous time t Ｓ The scanning unit 1010 is controlled to start a first scan (supplementary scan) at a future time t １ The future time estimation unit 1050 of this example estimates the future time t １ The second scan (repeated scan) in this example is performed at a future time t １The period L2 may be one cardiac cycle T at the shortest and two cardiac cycles 2T at the longest. The period L2 in this example is from the future time t when the second scan is started. １ From the next future time t ２ or a later time t Ｅ This is the period until

[0134] This aspect is configured to determine the start time of the first scan (supplementary scan) taking into account the time required for the first scan, and to start the second scan (main scan) immediately after the end of the first scan. This allows for a reduction in the time required for both the first and second scans. By combining the aforementioned reduction in the main scan time with this aspect and setting the length of the main scan time to a value between one cardiac cycle (T) and two cardiac cycles (2T), it is possible to further reduce the time required for both the first and second scans while reliably collecting data for one cardiac cycle. Furthermore, by setting the length of the main scan time to one cardiac cycle (T), it is possible to perform both the first and second scans in the shortest time possible while reliably collecting data for one cardiac cycle.

[0135] First scan data 1061 collected by the scan unit 1010 in the first scan is sent to the Doppler angle calculation unit 1070. The Doppler angle calculation unit 1070 is configured to calculate the Doppler angle in OCT blood flow measurement for the blood vessel of interest based on the first scan data 1061. For the calculation to calculate the Doppler angle, please refer to the Doppler angle calculation unit 233 described above.

[0136] The Doppler angle calculation unit 1070 is realized by cooperation between hardware including a circuit and Doppler angle calculation software. The ophthalmologic apparatus 1 of a non-limiting embodiment can realize the function of the Doppler angle calculation unit 1070 using the data processing unit 230 (the image generation unit 220, the vascular region identification unit 231, the Doppler angle calculation unit 233, etc.).

[0137] Second scan data 1062 collected by the scan unit 1010 in the second scan is sent to the hemodynamic information generation unit 1080. In addition, information on the Doppler angle calculated by the Doppler angle calculation unit 1070 is sent to the hemodynamic information generation unit 1080. The hemodynamic information generation unit 1080 generates hemodynamic information in the blood vessel of interest based on the second scan data 1062 and the Doppler angle.

[0138] For example, the hemodynamic information generating unit 1080 can generate a phase image of a cross section of interest based on the second scan data 1062 and calculate a blood flow velocity based on the phase image and the Doppler angle. Furthermore, the hemodynamic information generating unit 1080 can calculate a diameter (vascular diameter) of a blood vessel of interest in the cross section of interest and calculate a blood flow volume based on the blood vessel diameter and the blood flow velocity. The blood flow velocity and blood flow volume are non-limiting examples of hemodynamic information. The hemodynamic information generating unit 1080 may be capable of calculating other hemodynamic information.

[0139] The hemodynamic information generating unit 1080 is realized by cooperation between hardware including a circuit and hemodynamic information generating software. The ophthalmologic apparatus 1 of a non-limiting embodiment can realize the function of the hemodynamic information generating unit 1080 by using the data processing unit 230 (the image generating unit 220, the vascular region identifying unit 231, the blood flow velocity calculating unit 234, the vascular diameter calculating unit 235, the blood flow rate calculating unit 236, etc.).

[0140] The vessel of interest designation unit 1090 is configured to designate a vessel of interest to which OCT blood flow measurement is to be applied. In some aspects, the vessel of interest designation unit 1090 designates a vessel of interest to which OCT blood flow measurement is to be applied based on a vessel map representing the distribution of blood vessels in the fundus EF. The vessel map is generated from an OCT intensity image of the fundus EF. The process of generating the vessel map includes, for example, a process of extracting a vascular region from a three-dimensional OCT intensity image (stack data, volume data) of the fundus EF. The vessel of interest designation unit 1090 may be configured to select a vessel of interest from multiple blood vessels presented in the vessel map. The criterion for selecting a vessel of interest (selection criterion) may include an index related to the orientation of the vessel. Examples of vessel orientation indices include the Doppler angle and the suitability of the Doppler angle.

[0141] In some embodiments, the preferred value of the Doppler angle in OCT blood flow measurement is approximately 80 degrees, and in actual measurements, the search for the blood vessel and cross section of interest is performed with a target range of 77 degrees to 83 degrees. However, although measurements can be performed even when the Doppler angle is as small as 75 degrees, a problem occurs in that phase wrapping is more likely to occur, so it is considered desirable to set the lower limit of the target range to approximately 77 degrees. Furthermore, when the Doppler angle is as large as 85 degrees, a problem occurs in that the strength of the detected Doppler signal decreases, so it is considered desirable to set the upper limit of the target range to approximately 83 degrees. Note that this target range is a non-limiting example, and other target ranges may be used.

[0142] Considering these circumstances regarding the Doppler angle, the preferred range of the Doppler angle in OCT blood flow measurement is typically set to a range of 77 degrees to 83 degrees. This range is referred to as the acceptable Doppler angle range. The ophthalmic apparatus 1000 (e.g., the vessel of interest designation unit 1090 or the Doppler angle calculation unit 1070) can estimate the Doppler angle of each blood vessel displayed on the vascular map. For the calculation method, please refer to the Doppler angle calculation unit 233 of the ophthalmic apparatus 1 described above.

[0143] The vessel of interest designation unit 1090 compares the Doppler angle of each blood vessel displayed on the vascular map with the Doppler angle tolerance range. If the Doppler angle value of a certain blood vessel falls within the tolerance range, the vessel of interest designation unit 1090 determines that the Doppler angle of the certain blood vessel is good. If there are two or more blood vessels with good Doppler angles and only one blood vessel of interest is designated, the vessel of interest designation unit 1090 may be configured to select the blood vessel with the Doppler angle closest to the optimal value (typically 80 degrees). In some aspects, each blood vessel with a good Doppler angle may be designated as a blood vessel of interest. In some aspects, a predetermined number of blood vessels of interest may be selected from a plurality of blood vessels with good Doppler angles.

[0144] In addition to or instead of orientation information such as the Doppler angle or the favorability, the selection criteria may include other indices. Examples of other indices include the type of blood vessel (e.g., artery, vein), size (blood vessel diameter), tortuosity, and position (e.g., position relative to the optic disc). The blood vessel of interest designation unit 1090 can select a blood vessel of interest by considering two or more types of indices in stages or in parallel.

[0145] In another non-limiting example, the vessel of interest designation unit 1090 may be configured to designate a vessel selected by the user from among multiple blood vessels presented on a vascular map as the vessel of interest. In this example, the ophthalmic device 1000 displays a vascular map (a visualized image of the vascular map). The user can select a vessel of interest by referring to the displayed vascular map. The display of the vascular map and the input operation of the selected vessel of interest are performed using a user interface (e.g., the user interface 240 of the ophthalmic device 1) not shown.

[0146] The blood vessel of interest designation unit 1090 is realized by cooperation between hardware including a circuit and software for designating the blood vessel of interest. The ophthalmologic apparatus 1 according to a non-limiting embodiment can realize the function of the blood vessel of interest designation unit 1090 by using the data processing unit 230.

[0147] The alignment unit 1100 is configured to perform alignment to adjust the position of the scanning unit 1010 relative to the fundus Ef. For details about alignment, see the alignment optical system 50 described above. The alignment method is not limited to this. Any other alignment method may be adopted. After the alignment is completed, an operation (tracking) may be performed to maintain the suitable position of the scanning unit 1010 relative to the fundus Ef achieved by the alignment.

[0148] The alignment unit 1100 is realized by the cooperation of hardware including circuits, optical systems, and mechanisms with alignment software. The ophthalmologic apparatus 1 of a non-limiting embodiment can realize the functions of the alignment unit 1100 using the fundus camera unit 2 (alignment optical system 50), the control unit 210 (main control unit 211), and the data processing unit 230.

[0149] The scanning unit 1010 may perform at least a part of the aforementioned preparatory repetitive scan in parallel with the alignment performed by the alignment unit 1100. Furthermore, at least a part of the processing of data collected by the scanning unit 1010 in this preparatory repetitive scan (generation of phase images, identification of vascular regions, estimation of future time points) may be performed in parallel with the alignment.

[0150] The operation of the ophthalmic apparatus 1000 will be described. Fig. 10 shows one example of the operation of the ophthalmic apparatus 1000. The processing content of each step in this example of operation is not limited and may be modified as desired. Furthermore, the order of the steps in this example of operation is not limited and may be modified as desired.

[0151] First, in step S1, the blood vessel of interest designation unit 1090 designates a blood vessel of interest in the fundus oculi Ef. A cross section of interest, which is the target of application of the OCT scan, may also be designated.

[0152] In step S2, the alignment part 1100 starts aligning the scanning part 1010 with the fundus oculi Ef.

[0153] In step S3, the scan control unit 1020 controls the scan unit 1010 to apply a repeat scan to the blood vessel of interest designated in step S1. This repeat scan is a preparatory repeat scan.

[0154] In step S4, the phase image generating unit 1030 processes the data collected in the repeated scan in step S3 to generate a phase image.

[0155] In step S5, the vascular region specifying unit 1040 specifies a vascular region in the phase image generated in step S4.

[0156] When the above-described vascular map can be referenced, the range in which the vascular region exists in the phase image generated in step S4 can be identified from the vascular map. Furthermore, changes in pixel values ​​within the identified range due to heartbeat can be monitored in real time. The ophthalmologic apparatus 1000 can display the phase image and also display information indicating the monitoring range (e.g., a frame image indicating the outer edge of the range) on the phase image.

[0157] In step S6, the future time point estimation unit 1050 applies time series analysis to the vascular region identified in step S5 to estimate a future time point corresponding to a predetermined cardiac phase, and sets the start time points of the supplementary scan and the main scan based on this future time point.

[0158] In the examples of FIGS. 8 and 9, the future time estimation unit 1050 calculates the time between two past times t －ｎ and t －（ｎ＋１） , or past time t －ｎ and two past peak times. The future time point estimation unit 1050 calculates two past times t －ｎ and t －（ｎ＋１） , or two past peak times. The future time point estimation unit 1050 calculates the cardiac cycle T based on two past times t －ｎ and t －（ｎ＋１） , or past time t －ｎ and the cardiac cycle T, １ The future time point estimation unit 1050 estimates the future time point t １ and the start time t of the supplemental scan based on the known time required for the supplemental scan.Ｓ and the start time of the main scan t １ Set the following.

[0159] In step S7, it is determined whether the alignment started in step S2 has already been completed. If the alignment has already been completed (S7: Yes), the processing procedure proceeds to step S8.

[0160] The scan controller 1020 may detect the timing to start step S8 by monitoring the vascular region in the phase image. At this time, by storing sequentially acquired data in a ring buffer, this processing procedure can be executed using the data stored in the ring buffer even if data is missed or the start of measurement is delayed.

[0161] In step S8, the scan control unit 1020 determines the supplementary scan start time t Ｓ In response to the arrival of the main scanning start time t, the scanning unit 1010 is controlled to apply a supplementary scan to the first cross section (supplementary cross section) of the blood vessel of interest designated in step S1 and acquire first scan data 1061. The supplementary scan is performed at the main scanning start time t １ It ends just before.

[0162] In step S9, the scan control unit 1020 determines the main scanning start time t １ In response to the arrival of the time t, the scanning unit 1010 is controlled to apply a main scan (repeated scan) to the first cross section (cross section of interest) of the blood vessel of interest designated in step S1 to acquire second scan data 1062. Ｅ It ends at .

[0163] Main scanning end time t Ｅ is the start time of the main scanning t １ Time t after one cardiac cycle T has elapsed since ２ and the scanning start time t １ Time t, two cardiac cycles 2T after ３ The main scanning end time t Ｅ is the time t at which the shortest measurement time can be achieved. ２However, the main scanning end time t Ｅ is not limited to this.

[0164] In step S10, the Doppler angle calculation unit 1070 calculates the Doppler angle in the OCT scan for the blood vessel of interest based on the first scan data 1061 acquired in step S8.

[0165] In step S11, the hemodynamic information generating unit 1080 calculates the blood flow velocity in the blood vessel of interest based on the second scan data 1062 collected in step S9 and the Doppler angle calculated in step S10. The hemodynamic information generating unit 1080 calculates the diameter of the blood vessel of interest in the cross section of interest, and can calculate the blood flow volume based on this diameter and the blood flow velocity.

[0166] The ophthalmologic apparatus 1000 can display the blood flow dynamics information (blood flow velocity, blood flow volume, etc.) generated in step S11, the blood vessel diameter, the Doppler angle, an image of the subject's eye E (fundus oculi Ef), and the like.

[0167] According to the ophthalmologic device 1000 of this embodiment, the start point of fundus blood flow dynamics measurement can be suitably set without using a biological information monitor such as an electrocardiograph, and data for one cardiac cycle can be reliably collected in a short measurement time.

[0168] Other Embodiments It will be understood by those skilled in the art that the present disclosure also provides embodiments in categories other than ophthalmic devices. For example, the present disclosure may provide an embodiment of a method for controlling an ophthalmic device, an embodiment of a method for controlling an ophthalmic information processing device, an embodiment of a program for causing a computer to execute each step of any of the methods, and an embodiment of a computer-readable non-transitory recording medium on which any of the programs is recorded. The recording medium may take any form. For example, the recording medium may be any of a magnetic disk, an optical disk, a magneto-optical disk, and a semiconductor memory.

[0169] Some embodiments are a method for controlling an ophthalmologic apparatus having a scanning unit and a processor that performs OCT scans, and that performs OCT blood flow measurement to measure hemodynamics in fundus blood vessels. The method according to the present embodiment causes the processor to execute first scan control, phase image generation processing, vascular region identification processing, future time point estimation processing, second scan control, angle calculation processing, third scan control, and hemodynamic information generation processing. The first scan control controls the scanning unit to apply repeated scans to a blood vessel of interest in the fundus of the subject's eye to acquire data. The phase image generation processing processes the data acquired by the first scan control to generate a phase image. The vascular region identification processing identifies a blood vessel region in the phase image. The future time point estimation processing applies time series analysis to the identified blood vessel region to estimate a future time point corresponding to a predetermined cardiac phase. The second scan control controls the scanning unit to apply a first scan to a first cross-section of the blood vessel of interest to acquire first data before the estimated future time point arrives. The angle calculation process calculates the Doppler angle in OCT blood flow measurement for the blood vessel of interest based on first data collected in the first scan. The third scan control controls the scanning unit to apply a second scan to a second cross section of the blood vessel of interest to collect second data when the estimated future time arrives. The hemodynamic information generation process generates hemodynamic information for the blood vessel of interest based on the second data collected in the second scan and the Doppler angle calculated in the angle calculation process.

[0170] It is possible to configure a program that causes an ophthalmic device including a computer to execute the method according to this embodiment. It is also possible to create a computer-readable non-transitory recording medium on which such a program is recorded. This non-transitory recording medium may be in any form, such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory. Any of the features described in this disclosure may be combined with the method, program, and recording medium according to this embodiment.

[0171] Although several embodiments according to the present disclosure have been described above with reference to the drawings, these are non-limiting examples, and various configurations other than those described above may also be adopted.

[0172] In addition, in the flowcharts used in the above description, multiple steps (processes) are described in order. However, the order of the steps performed in each embodiment is not limited to the order described. In each embodiment, the order of the steps shown in the drawings can be changed to the extent that the content is not affected. Furthermore, the above embodiments can be at least partially combined to the extent that the content is not contradictory.

[0173] Some or all of the above embodiments can be described as follows: However, the embodiments according to the present disclosure are not limited to the following supplementary notes.

[0174] [1] An ophthalmic device that performs optical coherence tomography blood flow measurement to measure blood flow dynamics in blood vessels at the fundus of an eye, comprising: a scanning unit that applies repeated scans to a blood vessel of interest at the fundus of an eye to collect data; a phase image generating unit that processes the data to generate a phase image; a blood vessel region identifying unit that identifies a blood vessel region in the phase image; a future time point estimating unit that applies time series analysis to the blood vessel region to estimate a future time point corresponding to a predetermined cardiac time phase; a scan control unit that controls the scanning unit to apply a first scan to a first cross section of the blood vessel of interest to collect first data before the future time point arrives, and to control the scanning unit to apply a second scan to a second cross section of the blood vessel of interest to collect second data when the future time point arrives; an angle calculating unit that calculates a Doppler angle in optical coherence tomography blood flow measurement for the blood vessel of interest based on the first data; and a blood flow dynamics information generating unit that generates blood flow dynamics information in the blood vessel of interest based on the second data and the Doppler angle.

[0175] [2] The ophthalmologic apparatus of claim 1, wherein the future time point estimation unit applies the time series analysis to the vascular region to obtain a cardiac cycle, and the scan control unit controls the scan unit to start the second scan at the future time point and end the second scan at a time point between a time point when one cardiac cycle has elapsed and a time point when two cardiac cycles have elapsed from the future time point.

[0176] [3] The ophthalmologic apparatus according to claim 2, wherein the scan control unit controls the scan unit to start the second scan at the future time point and to end the second scan at a time point when one cardiac cycle has elapsed from the future time point.

[0177] [4] The ophthalmologic device according to any one of [1] to [3] above, wherein the future time point estimation unit applies the time series analysis to the vascular region to obtain a cardiac cycle and a past time point corresponding to the cardiac time phase, and estimates the future time point based on the cardiac cycle and the past time point.

[0178] [5] The ophthalmologic apparatus according to any one of [1] to [4] above, wherein the scan control unit controls the scan unit to start the first scan at a time point earlier than the future time point by a predetermined time required for the first scan, and to start the second scan immediately after the end of the first scan.

[0179] [6] The ophthalmologic device according to any one of 1 to 5 above, further comprising an alignment unit that performs alignment to adjust the position of the scanning unit relative to the fundus, and the scanning unit performs the repeated scan of the blood vessel of interest in parallel with the alignment.

[0180] [7] The ophthalmologic apparatus according to the above item 6, wherein after the alignment is completed, the scan control unit causes the scan unit to execute the first scan and the second scan.

[0181] [8] The ophthalmologic apparatus according to any one of the above items 1 to 7, further comprising a target blood vessel designation unit that designates the target blood vessel.

[0182] [9] A method for controlling an ophthalmologic apparatus having a scanning unit and a processor that performs optical coherence tomography scans, and that performs optical coherence tomography blood flow measurement to measure blood flow dynamics in blood vessels at the fundus of the eye, comprising: a first scanning control that controls the scanning unit to apply repeated scans to a blood vessel of interest at the fundus of the eye to collect data; a phase image generating process that processes the data to generate a phase image; a blood vessel region identifying process that identifies a blood vessel region in the phase image; a future time point estimation process that applies time series analysis to the blood vessel region to estimate a future time point corresponding to a predetermined cardiac phase; a second scanning control that controls the scanning unit to apply a first scan to a first cross section of the blood vessel of interest to collect first data before the future time point arrives; an angle calculating process that calculates a Doppler angle in optical coherence tomography blood flow measurement for the blood vessel of interest based on the first data; and a third scanning control that controls the scanning unit to apply a second scan to a second cross section of the blood vessel of interest to collect second data when the future time point arrives. and executing a hemodynamic information generation process for generating hemodynamic information in the blood vessel of interest based on the second data and the Doppler angle.

[0183]

[10] A program for causing a computer to execute the method of 9 above.

[0184]

[11] A computer-readable non-transitory recording medium on which the program of 10 above is recorded.

[0185] The present disclosure is merely an example of how to implement the present invention, and those who intend to implement the present invention can make any modifications (omissions, substitutions, additions, etc.) within the scope of the gist of the present invention.

[0186] REFERENCE SIGNS LIST 1000 Ophthalmic apparatus 1010 Scan unit 1020 Scan control unit 1030 Phase image generation unit 1040 Blood vessel region identification unit 1050 Future time point estimation unit 1070 Doppler angle calculation unit 1080 Blood flow dynamics information generation unit 1090 Blood vessel of interest designation unit 1100 Alignment unit

Claims

1. An ophthalmic device that performs optical coherence tomography blood flow measurement to measure blood flow dynamics in blood vessels at the fundus of an eye, comprising: a scanning unit that applies repeated scans to a blood vessel of interest at the fundus of an eye to collect data; a phase image generating unit that processes the data to generate a phase image; a blood vessel region identifying unit that identifies a blood vessel region in the phase image; a future time point estimating unit that applies time series analysis to the blood vessel region to estimate a future time point corresponding to a predetermined cardiac phase; a scan control unit that controls the scanning unit to apply a first scan to a first cross section of the blood vessel of interest to collect first data before the future time point arrives, and to control the scanning unit to apply a second scan to a second cross section of the blood vessel of interest to collect second data when the future time point arrives; an angle calculating unit that calculates a Doppler angle in optical coherence tomography blood flow measurement for the blood vessel of interest based on the first data; and a blood flow dynamics information generating unit that generates blood flow dynamics information in the blood vessel of interest based on the second data and the Doppler angle.

2. The ophthalmologic apparatus of claim 1, wherein the future time point estimation unit applies the time series analysis to the vascular region to determine a cardiac cycle, and the scan control unit controls the scan unit to start the second scan at the future time point and end the second scan at a time point between when one cardiac cycle has elapsed and when two cardiac cycles have elapsed from the future time point.

3. The ophthalmologic apparatus according to claim 2, wherein the scan control unit controls the scan unit so as to start the second scan at the future time point and to end the second scan at a time point when one cardiac cycle has elapsed from the future time point.

4. An ophthalmologic device according to any one of claims 1 to 3, wherein the future time point estimation unit applies the time series analysis to the vascular region to obtain a cardiac cycle and a past time point corresponding to the cardiac time phase, and estimates the future time point based on the cardiac cycle and the past time point.

5. An ophthalmologic device according to any one of claims 1 to 4, wherein the scan control unit controls the scan unit to start the first scan at a time point earlier than the future time point by a predetermined time required for the first scan, and to start the second scan immediately after the end of the first scan.

6. An ophthalmologic device according to any one of claims 1 to 5, further comprising an alignment unit that performs alignment to adjust the position of the scanning unit relative to the fundus, and the scanning unit performs the repeated scan of the blood vessel of interest in parallel with the alignment.

7. The ophthalmologic apparatus according to claim 6, wherein after the alignment is completed, the scan control unit causes the scan unit to execute the first scan and the second scan.

8. The ophthalmologic apparatus according to any one of claims 1 to 7, further comprising a target blood vessel designation unit that designates the target blood vessel.

9. A method for controlling an ophthalmic device having a scanning unit and a processor that performs optical coherence tomography scans, and that performs optical coherence tomography blood flow measurement to measure blood flow dynamics in blood vessels at the fundus of the eye, comprising: a first scan control that controls the scanning unit to apply repeated scans to a blood vessel of interest at the fundus of the eye to collect data; a phase image generation process that processes the data to generate a phase image; a blood vessel region identification process that identifies a blood vessel region in the phase image; a future time point estimation process that applies time series analysis to the blood vessel region to estimate a future time point corresponding to a predetermined cardiac phase; a second scan control that controls the scanning unit to apply a first scan to a first cross section of the blood vessel of interest to collect first data before the future time point arrives; an angle calculation process that calculates a Doppler angle in optical coherence tomography blood flow measurement for the blood vessel of interest based on the first data; and a third scan control that controls the scanning unit to apply a second scan to a second cross section of the blood vessel of interest to collect second data when the future time point arrives. and executing a hemodynamic information generation process for generating hemodynamic information in the blood vessel of interest based on the second data and the Doppler angle.

10. A program for causing a computer to execute the method of claim 9.

11. A computer-readable non-transitory recording medium on which the program of claim 10 is recorded.

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