JP2017143994A - Ophthalmologic imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ophthalmologic imaging device capable of detecting a blood flow with high sensitivity even when the blood flow is slow in speed.SOLUTION: An ophthalmologic imaging device is capable of performing OCT of ocular fundus by a scan pattern in which a plurality of lines are arranged, and includes a data collection part, an optical scanner, a control part, and an image forming part. The data collection part is configured to project a measurement light onto the ocular fundus, detect an interference light of the return light and a reference light, and collect the detection data. The optical scanner is configured to deflect the measurement light two-dimensionally. The control part is configured to control the optical scanner so as to scan a plurality of lines a predetermined number of times in the order different from the arrangement order of the plurality of lines. The image forming part is configured to form an angiographic image in which a blood vessel of the ocular fundus is emphasized based on detection data collected by the data collection part while control of the optical scanner is being performed by the control part.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an ophthalmologic photographing apparatus.

  Image diagnosis occupies an important position in the field of ophthalmology. In recent years, the use of optical coherence tomography (OCT) has progressed. OCT has been used not only for acquiring B-mode images and three-dimensional images of the eye to be examined, but also for acquiring front images (en-face images) such as C-mode images and shadowgrams. Moreover, acquiring the image which emphasized the specific site | part of the eye to be examined, and acquiring functional information are also performed.

  For example, OCT angiography (OCT-Angiography) that forms an image in which retinal blood vessels and choroidal blood vessels are emphasized is attracting attention (see, for example, Patent Document 1). In OCT angiography, the same region (same cross section) of the fundus is scanned a plurality of times. In general, the tissue (structure) of the scan site is not changed in time, but the blood flow portion inside the blood vessel changes in time. In OCT angiography, an image is formed by emphasizing a portion (blood flow signal) where such a temporal change exists. By executing such repeated scanning and signal processing for a plurality of cross sections, a three-dimensional distribution of the fundus blood vessel is obtained.

Special table 2015-515894 gazette

  In ophthalmic OCT, measurement light having a center wavelength in the near-infrared region is generally used, but the measurement light may contain a visible component. When performing fundus OCT using measurement light including a visible component, the eye to be examined follows the movement locus of the measurement light, and data on the target part may not be acquired.

  For example, in OCT angiography, a raster scan is often applied in order to collect data of a three-dimensional region of the fundus, and conventional ophthalmologic imaging apparatuses have a plurality of lines arranged in parallel to each other in the order of arrangement. Scanning every time. For this reason, a red linear image that moves in the arrangement direction of a plurality of lines may be chased by the eyes.

  In OCT angiography, the same cross section is scanned multiple times to detect temporal changes in blood flow, and this is imaged. However, in conventional ophthalmic imaging devices, the same cross section is scanned continuously, When the blood flow is slow, the temporal change may not be sufficiently detected. In order to solve this, it is conceivable to reduce the repetition rate of continuous scanning of the same cross section, but a new problem that the measurement time becomes longer occurs. This problem is particularly noticeable when a three-dimensional region is targeted.

  An object of the ophthalmologic photographing apparatus according to the present invention is to detect a blood flow with high sensitivity even when the blood flow is slow.

  The ophthalmologic photographing apparatus of the embodiment can perform optical coherence tomography (OCT) of the fundus with a scan pattern in which a plurality of lines are arranged, and includes a data collection unit, an optical scanner, a control unit, and an image forming unit. Is provided. The data collection unit is configured to project measurement light onto the fundus, detect interference light between the return light and the reference light, and collect the detection data. The optical scanner is configured to be able to deflect measurement light two-dimensionally. The control unit is configured to control the optical scanner so as to scan the plurality of lines a predetermined number of times in an order different from the arrangement order of the plurality of lines. The image forming unit is configured to form an angiographic image in which the blood vessels of the fundus are emphasized based on the detection data collected by the data collecting unit while controlling the optical scanner by the control unit.

  According to the embodiment, the blood flow can be detected with high sensitivity even when the blood flow is at a low speed.

Schematic showing an example of a structure of the ophthalmologic imaging apparatus which concerns on embodiment. Schematic showing an example of a structure of the ophthalmologic imaging apparatus which concerns on embodiment. Schematic showing an example of a structure of the ophthalmologic imaging apparatus which concerns on embodiment. Schematic for demonstrating an example of a structure of the ophthalmologic imaging device which concerns on embodiment. Schematic for demonstrating an example of a structure of the ophthalmologic imaging device which concerns on embodiment. The flowchart showing an example of operation | movement of the ophthalmologic imaging device which concerns on embodiment.

  Several embodiments of the present invention will be described in detail with reference to the drawings. The ophthalmologic imaging apparatus according to the embodiment is an ophthalmologic apparatus having a function of executing at least optical coherence tomography (OCT). In particular, the ophthalmic imaging apparatus of the embodiment is used for OCT angiography of the fundus.

  Hereinafter, an ophthalmologic photographing apparatus in which a swept source OCT and a fundus camera are combined will be described, but the embodiment is not limited thereto. For example, the type of OCT is not limited to the swept source OCT, and may be a spectral domain OCT or the like. Here, the swept source OCT divides the light from the wavelength sweep type (wavelength scanning type) light source into the measurement light and the reference light, and causes the return light of the measurement light from the test object to interfere with the reference light to cause interference light. The interference light is detected by a balanced photodiode or the like, and an image is formed by performing Fourier transform or the like on the detection data collected according to the wavelength sweep and the measurement light scan. Spectral domain OCT splits light from a low-coherence light source into measurement light and reference light, and causes interference light to be generated by interfering the return light of the measurement light from the test object with the reference light. This is a technique in which a distribution is detected by a spectroscope and an image is formed by applying Fourier transform or the like to the detected spectral distribution.

  The ophthalmologic photographing apparatus may or may not have a function of acquiring a photograph (digital photograph) of the eye to be examined like a fundus camera. Further, instead of the fundus camera, a scanning laser ophthalmoscope (SLO), a slit lamp microscope, an anterior segment imaging camera, a surgical microscope, or the like may be provided. The fundus photograph can be used for fundus observation, scan area setting, tracking, and the like.

<Constitution>
As shown in FIG. 1, the ophthalmologic photographing apparatus 1 includes a fundus camera unit 2, an OCT unit 100, and an arithmetic control unit 200. The fundus camera unit 2 is provided with an optical system that is substantially the same as that of a conventional fundus camera. The OCT unit 100 is provided with an optical system and a mechanism for performing OCT. The arithmetic control unit 200 includes a processor. A chin rest and a forehead support for supporting the face of the subject are provided at positions facing the fundus camera unit 2.

  In this specification, the “processor” is, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), or a programmable logic device (for example, SPLD (Simple ProLigL). It means a circuit such as Programmable Logic Device (FPGA) or Field Programmable Gate Array (FPGA). For example, the processor implements the functions according to the embodiment by reading and executing a program stored in a storage circuit or a storage device.

<Fundus camera unit 2>
The fundus camera unit 2 is provided with an optical system and mechanism for photographing the fundus oculi Ef of the eye E to be examined. Images obtained by photographing the fundus oculi Ef (called fundus images, fundus photographs, etc.) include observation images and photographed images. The observation image is obtained, for example, by moving image shooting using near infrared light. The captured image is, for example, a color image or monochrome image obtained using visible flash light, or a monochrome image obtained using near-infrared flash light. The fundus camera unit 2 may be able to acquire a fluorescein fluorescent image, an indocyanine green fluorescent image, a spontaneous fluorescent image, or the like.

  The fundus camera unit 2 includes an illumination optical system 10 and a photographing optical system 30. The illumination optical system 10 irradiates the eye E with illumination light. The imaging optical system 30 detects the return light of the illumination light from the eye E. The measurement light from the OCT unit 100 is guided to the eye E through the optical path in the fundus camera unit 2, and the return light is guided to the OCT unit 100 through the same optical path.

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

  The return light of the observation illumination light from the eye E is refracted by the objective lens 22, passes through the dichroic mirror 46, passes through the hole formed in the central region of the perforated mirror 21, and passes through the dichroic mirror 55. The light is reflected by the mirror 32 via the photographing focusing lens 31. Further, the return light passes through the half mirror 33A, is reflected by the dichroic mirror 33, and forms an image on the light receiving surface of the CCD image sensor 35 by the condenser lens. The CCD image sensor 35 detects the return light at a predetermined frame rate, for example. Note that an observation image of the fundus oculi Ef is obtained when the photographing optical system 30 is focused on the fundus oculi Ef, and an anterior eye observation image is obtained when the focus is on the anterior eye segment.

  The imaging light source 15 is a visible light source including, for example, a xenon lamp or an LED. The light (imaging illumination light) output from the imaging light source 15 is applied to the fundus oculi Ef through the same path as the observation illumination light. The return light of the imaging illumination light from the eye E is guided to the dichroic mirror 33 through the same path as the return light of the observation illumination light, passes through the dichroic mirror 33, is reflected by the mirror 36, and is reflected by the condenser lens 37. An image is formed on the light receiving surface of the CCD image sensor 38.

  The LCD 39 displays a fixation target for fixing the eye E to be examined. A part of the light beam (fixed light beam) output from the LCD 39 is reflected by the half mirror 33A, reflected by the mirror 32, and passes through the photographing focusing lens 31 and the dichroic mirror 55, and then the hole of the aperture mirror 21. Pass through the department. The fixation light beam that has passed through the hole of the aperture mirror 21 passes through the dichroic mirror 46, is refracted by the objective lens 22, and is projected onto the fundus oculi Ef. By changing the display position of the fixation target on the screen of the LCD 39, the fixation position of the eye E can be changed. Instead of the LCD 39, a matrix LED in which a plurality of LEDs are arranged two-dimensionally, a combination of a light source and a variable aperture (liquid crystal aperture, etc.), etc. can be used as the fixation light flux generating means.

  The fundus camera unit 2 is provided with an alignment optical system 50 and a focus optical system 60. The alignment optical system 50 generates an alignment index used for alignment of the optical system with respect to the eye E. The focus optical system 60 generates a split index used for focus adjustment with respect to the eye E.

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

  The cornea-reflected light of the alignment light passes through the objective lens 22, the dichroic mirror 46, and the hole, part of which passes through the dichroic mirror 55, passes through the photographing focusing lens 31, is reflected by the mirror 32, and is half The light passes through the mirror 33A, is reflected by the dichroic mirror 33, and is projected onto the light receiving surface of the CCD image sensor 35 by the condenser lens. Based on the received light image (alignment index image) by the CCD image sensor 35, manual alignment and auto alignment similar to the conventional one can be performed.

  The focus optical system 60 is moved along the optical path (illumination optical path) of the illumination optical system 10 in conjunction with the movement of the imaging focusing lens 31 along the optical path (imaging optical path) of the imaging optical system 30. The reflection bar 67 can be inserted into and removed from the illumination optical path.

  When performing the focus adjustment, the reflection surface of the reflection bar 67 is obliquely provided in the illumination optical path. The focus light output from the LED 61 passes through the relay lens 62, is separated into two light beams by the split target plate 63, passes through the two-hole aperture 64, is reflected by the mirror 65, and is reflected by the condenser lens 66. An image is once formed on the reflection surface 67 and reflected. Further, the focus light passes through the relay lens 20, is reflected by the perforated mirror 21, passes through the dichroic mirror 46, is refracted by the objective lens 22, and is projected onto the fundus oculi Ef.

  The fundus reflection light of the focus light is detected by the CCD image sensor 35 through the same path as the corneal reflection light of the alignment light. Based on the received image (split index image) by the CCD image sensor 35, manual alignment and auto-alignment similar to the conventional one can be performed.

  The photographing optical system 30 includes diopter correction lenses 70 and 71. The diopter correction lenses 70 and 71 can be selectively inserted into a photographing optical path between the perforated mirror 21 and the dichroic mirror 55. The diopter correction lens 70 is a plus (+) lens for correcting intensity hyperopia, for example, a + 20D (diopter) convex lens. The diopter correction lens 71 is a minus (−) lens for correcting intensity myopia, for example, a −20D concave lens. The diopter correction lenses 70 and 71 are mounted on, for example, a turret plate. The turret plate is formed with a hole for the case where none of the diopter correction lenses 70 and 71 is applied.

  The dichroic mirror 46 combines the fundus imaging optical path and the OCT optical path. The dichroic mirror 46 reflects light in a wavelength band used for OCT and transmits light for fundus photographing. In the optical path for OCT, a collimator lens unit 40, an optical path length changing unit 41, an optical scanner 42, an OCT focusing lens 43, a mirror 44, and a relay lens 45 are provided in this order from the OCT unit 100 side.

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

  The optical scanner 42 is disposed at a position optically conjugate with the pupil of the eye E. The optical scanner 42 changes the traveling direction of the measurement light LS that passes through the optical path for OCT. Thereby, the eye E is scanned with the measurement light LS. The optical scanner 42 can deflect the measurement light LS in an arbitrary direction on the xy plane, and includes, for example, a galvanometer mirror that deflects the measurement light LS in the x direction and a galvanometer mirror that deflects the measurement light LS in the y direction.

<OCT unit 100>
As illustrated in FIG. 2, the OCT unit 100 is provided with an optical system for performing OCT of the eye E. The configuration of this optical system is the same as that of the conventional swept source OCT. That is, this optical system divides the light from the wavelength sweep type (wavelength scanning type) light source into the measurement light and the reference light, and returns the return light of the measurement light from the eye E and the reference light via the reference light path. An interference optical system that generates interference light by causing interference and detects the interference light is included. A detection result (detection signal) obtained by the interference optical system is a signal indicating the spectrum of the interference light, and is sent to the arithmetic control unit 200.

  The light source unit 101 includes a wavelength swept type (wavelength scanning type) light source that changes the wavelength of the emitted light at a high speed, like a general swept source OCT. The wavelength sweep type light source is, for example, a near infrared laser light source.

  The light L0 output from the light source unit 101 is guided to the polarization controller 103 by the optical fiber 102 and its polarization state is adjusted. Further, the light L0 is guided to the fiber coupler 105 by the optical fiber 104 and is divided into the measurement light LS and the reference light LR.

  The reference light LR is guided to the collimator 111 by the optical fiber 110 and converted into a parallel light beam, and is guided to the corner cube 114 via the optical path length correction member 112 and the dispersion compensation member 113. The optical path length correction member 112 acts to match the optical path length of the reference light LR and the optical path length of the measurement light LS. The dispersion compensation member 113 acts to match the dispersion characteristics between the reference light LR and the measurement light LS.

  The corner cube 114 turns the traveling direction of the incident reference light LR in the reverse direction. The incident direction and the emitting direction of the reference light LR with respect to the corner cube 114 are parallel to each other. The corner cube 114 is movable in the incident direction of the reference light LR, and thereby the optical path length of the reference light LR is changed.

  1 and 2, the optical path length changing unit 41 for changing the length of the optical path (measurement optical path, measurement arm) of the measurement light LS and the optical path (reference optical path, reference arm) of the reference light LR are used. Both corner cubes 114 for changing the length are provided, but only one of the optical path length changing unit 41 and the corner cube 114 may be provided. It is also possible to change the difference between the measurement optical path length and the reference optical path length using optical members other than these.

  The reference light LR that has passed through the corner cube 114 passes through the dispersion compensation member 113 and the optical path length correction member 112, is converted from a parallel light beam to a focused light beam by the collimator 116, and enters the optical fiber 117. The reference light LR incident on the optical fiber 117 is guided to the polarization controller 118 and its polarization state is adjusted. The reference light LR is guided to the attenuator 120 by the optical fiber 119 and the amount of light is adjusted, and is guided to the fiber coupler 122 by the optical fiber 121. It is burned.

  On the other hand, the measurement light LS generated by the fiber coupler 105 is guided by the optical fiber 127 and converted into a parallel light beam by the collimator lens unit 40, and the optical path length changing unit 41, the optical scanner 42, the OCT focusing lens 43, and the mirror 44. Then, the light passes through the relay lens 45, is reflected by the dichroic mirror 46, is refracted by the objective lens 22, and enters the eye E to be examined. The measurement light LS is scattered and reflected at various depth positions of the eye E. The return light of the measurement light LS from the eye E travels in the reverse direction on the same path as the forward path, is guided to the fiber coupler 105, and reaches the fiber coupler 122 via the optical fiber 128.

  The fiber coupler 122 combines (interferes) the measurement light LS incident through the optical fiber 128 and the reference light LR incident through the optical fiber 121 to generate interference light. The fiber coupler 122 generates a pair of interference light LC by branching the interference light at a predetermined branching ratio (for example, 1: 1). The pair of interference lights LC are guided to the detector 125 through optical fibers 123 and 124, respectively.

  The detector 125 is, for example, a balanced photodiode (Balanced Photo Diode). The balanced photodiode has a pair of photodetectors that respectively detect the pair of interference lights LC, and outputs a difference between detection results obtained by these. The detector 125 sends the detection result (detection signal) to a DAQ (Data Acquisition System) 130.

  The clock 130 is supplied from the light source unit 101 to the DAQ 130. The clock KC is generated in synchronization with the output timing of each wavelength swept within a predetermined wavelength range by the wavelength sweep type light source in the light source unit 101. For example, the light source unit 101 optically delays one of the two branched lights obtained by branching the light L0 of each output wavelength, and then generates a clock KC based on the result of detecting these combined lights. Generate. The DAQ 130 samples the detection signal input from the detector 125 based on the clock KC. The DAQ 130 sends the sampling result of the detection signal from the detector 125 to the arithmetic control unit 200.

<Calculation control unit 200>
The arithmetic control unit 200 controls each part of the fundus camera unit 2, the display device 3, and the OCT unit 100. The arithmetic control unit 200 executes various arithmetic processes. For example, the arithmetic control unit 200 performs signal processing such as Fourier transform on the spectrum distribution based on the detection result obtained by the detector 125 for each series of wavelength scans (for each A line). A reflection intensity profile is formed. Furthermore, the arithmetic control unit 200 forms image data by imaging the reflection intensity profile of each A line. The arithmetic processing for that is the same as the conventional swept source OCT.

  The arithmetic control unit 200 includes, for example, a processor, a RAM (Random Access Memory), a ROM (Read Only Memory), a hard disk drive, a communication interface, and the like. Various computer programs are stored in a storage device such as a hard disk drive. The arithmetic control unit 200 may include an operation device, an input device, a display device, and the like.

<Control system>
A configuration example of the control system of the ophthalmologic photographing apparatus 1 is shown in FIG.

<Control unit 210>
The control unit 210 controls each unit of the ophthalmologic photographing apparatus 1. Control unit 210 includes a processor. The control unit 210 is provided with a main control unit 211 and a storage unit 212.

<Main control unit 211>
The main control unit 211 performs various controls. For example, the main control unit 211 includes an imaging focusing lens 31, CCDs (image sensors) 35 and 38, an LCD 39, an optical path length changing unit 41, an optical scanner 42, an OCT focusing lens 43, a focus optical system 60, a reflector 67, The light source unit 101, the reference driving unit 114A, the detector 125, the DAQ 130, and the like are controlled. The reference driving unit 114A moves the corner cube 114 provided in the reference optical path. Thereby, the length of the reference optical path is changed.

<Storage unit 212>
The storage unit 212 stores various data. Examples of the data stored in the storage unit 212 include image data of an OCT image, image data of a fundus image, and eye information to be examined. The eye information includes subject information such as patient ID and name, left / right eye identification information, electronic medical record information, and the like.

  Further, the storage unit 212 stores scan information 212a in advance. The scan information 212a records scan conditions for one or more scan patterns. When the scan pattern includes a plurality of lines, the scan condition of the scan pattern includes information (scan order information) indicating an order when the plurality of lines are sequentially scanned.

  A specific example of the scan order information will be described with reference to FIGS. 4A and 4B. 4A shows a raster scan (three-dimensional scan) 300 in which a plurality of lines 300-1, 300-2, 300-3,..., 300-N are arranged in parallel to each other. FIG. 4B shows scan order information 212 b created in advance for the raster scan 300. The scan order information 212b associates the arrangement order n of the N lines 300-n (n = 1 to N) included in the raster scan 300 with the scan order m. As shown in FIG. 4A, the arrangement order n is a natural order representing the spatial arrangement of N lines 300-n (n = 1 to N). The scan order m is a temporal order when the scans along the N lines 300-n (n = 1 to N) are sequentially performed.

  An interval (spacing) between N lines 300-n (n = 1 to N) shown in FIG. 4A, that is, a distance between adjacent lines 300-n and 300- (n + 1) can be arbitrarily set. . For example, the interval between the N lines 300-n (n = 1 to N) may or may not be constant.

  In OCT angiography, scanning of each line 300-n is repeated a predetermined number of times (for example, four times). In this case, for example, N lines 300-n (n = 1 to N) can be scanned so as to satisfy any of the following conditions: (Condition 1) The order indicated by the scan order m A series of scans of N lines 300-n (n = 1 to N) is executed, and this series of scans is repeated a predetermined number of times; (Condition 2) N lines 300-n in the order indicated by the scan order m While switching (n = 1 to N), the scanning of each line 300-n is continuously performed a predetermined number of times; (Condition 3) The scanning of each line 300-n is continuously performed a predetermined number of times (the number of times less than the predetermined number). A series of scans for switching the N lines 300-n (n = 1 to N) in the order indicated by the scan order m is performed, and the series of scans until the number of scans of each line 300-n reaches a predetermined number. repeat.

In the scan order information 212b, the scan order _mn is associated with the array order n (n = 1 to N). The N scan orders m ₁ , m ₂ , m ₃ ,..., _{M N} are different in scan order m _n1 and m _{n2 for} any different arrangement order n1 and n2. The number of array order n and the number of scan order _mn are both N. In other words, the scan order information 212b of this example gives a permutation “n → _mn ” of N lines 300-n (n = 1 to N) included in the raster scan, and N The spatial order of the lines 300-n (n = 1 to N) is converted into a temporal order. Further, this conversion (replacement) is not an identity conversion (that is, there are at least two n where n ≠ _mn ).

  The replacement for creating the scan order information 212b may be, for example, regular replacement or irregular replacement. An example of regular replacement can be constructed as follows. First, a set consisting of the arrangement order n = 1 to N is divided into K subsets including the same number of elements (2 ≦ K <N and N / K = integer). Next, the K subsets are ordered, and the elements (elements) of each subset are ordered. And order all the elements as follows: the first element of the first subset, the first element of the second subset,..., The first element of the Kth subset, The second element of the first subset, the second element of the second subset,..., The second element of the Kth subset, the third element of the first subset,. ..., the (N / K-1) th element of the Kth subset, the (N / K) th element of the first subset, ..., the (N / K) th element of the Kth subset The origin of. In OCT angiography, a series of scans for N lines 300-n (n = 1 to N) can be executed in this order, and this series of scans can be repeated a predetermined number of times.

  As another example of regular replacement, the replacement is configured such that one end side and the other end side of the array of the plurality of lines 300-n (n = 1 to N) are alternately scanned in order from the outside toward the inside. can do. That is, the substitution defined by “1 → 1, 2 → N, 3 → 2, 4 → N−1, 5 → 3,..., N → N / 2 or (N−1) / 2” is applied. can do. Here, “N → N / 2” is applied when N is an even number, and “N → (N−1) / 2” is applied when N is an odd number. In addition, the above is an illustration and regular substitution is not limited to these.

  On the other hand, irregular replacement is set based on, for example, a pseudo-random number sequence. The pseudo random number sequence is generated by a known pseudo random number sequence generation method (pseudo random number sequence generator). Examples of pseudo-random number sequence generation methods include the squaring method, linear congruence method (multiplication congruence method, mixed congruence method), linear feedback shift register, Mersenne Twister, multiplication with carry, Xorshift, Lagged Fibonacci method, Blum-Blum- There are Shub (BBS) and Fortuna. Alternatively, the scan order information 212b can be created by a manufacturer or user of the ophthalmologic photographing apparatus arbitrarily replacing the arrangement order (permute). In addition, the above is an illustration and irregular substitution is not limited to these.

  Thus, in OCT angiography, for example, a plurality of lines 300-n (n = 1 to N) included in a raster scan as shown in FIG. 4A are sequentially scanned. In order to extract a weak blood flow signal, rather than obtaining a blood flow signal from a plurality of images obtained by repeatedly scanning the same part at a short time interval, a plurality of images obtained at a relatively long time interval are obtained. The amount of change can be reliably captured by extracting temporal changes. In order to lengthen the scan time interval for the same part, the optical scanner 42 is controlled so that a plurality of scans of the part are performed continuously and at a time interval. Performing the scan can optimize the entire scan (for example, shortening the total photographing time). Therefore, in the OCT angiography, the scan order m of the plurality of lines 300-n (n = 1 to N) is set in advance so that the imaging time and the imaging flow are optimized, and based on the scan order information 212b (FIG. 4B). ) Is created. Note that the scan order in this case may be random, but the regular order is considered to be relatively effective.

Further, in the permutation of the array order n = 1 to n, two or more consecutive array orders n, n + 1,..., N + i (i is an arbitrary integer between 1 and N−1) are in the scan order _mn . The scan order information 212b can be created so as not to be continuous. Alternatively, the scan order information 212b can be created so that a predetermined number of such continuous arrays are included at most. Further, the scan order information 212b can be created so that the scan orders m _n and m _{n + 1} corresponding to two consecutive arrangement orders n and n + 1 are arranged apart from each other by a predetermined interval. In the scan order information creation method exemplified here, lines 300-n to 300- (n + j) (j is an arbitrary integer between 1 and N-1) in which spatial arrangements are continuous are temporally continuous. It is an example of the device for avoiding being scanned as much as possible. Any device for achieving this object can be applied in the creation of scan order information.

  The scan order information is not limited to the above example. For example, even if the scan pattern is other than the raster scan, the scan order information can be generated in the same manner as in this example as long as the scan pattern includes a plurality of lines. Examples of such scan patterns include a radial scan in which a plurality of lines are arranged radially, a multi-cross scan composed of two groups of lines orthogonal to each other (for example, a group of five lines parallel to each other), and a diameter There is a concentric scan in which a plurality of different circles are arranged concentrically.

  Further, even with the same line arrangement, scan patterns corresponding to the size, shape and interval can be individually provided. For example, a raster scan in which a plurality of lines are arranged in parallel to each other in a square area and a raster scan in which a plurality of lines are arranged in parallel to a rectangular area can be provided. Further, even in the case of a square area raster scan, for example, a raster scan having a size of 6 mm × 6 mm and a raster scan having a size of 9 mm × 9 mm can be provided.

  The scan information 212a may include a plurality of scan order information. Here, two or more scan order information may be provided for the same scan pattern, or scan order information may be provided for each of two or more different scan patterns. When a plurality of scan order information is included in the scan information 212a, the scan order information corresponding to a preset scan pattern is selected by the main control unit 211, for example. When two or more pieces of scan order information are provided for one scan pattern, for example, scan order information applied to the eye E in the past (for example, a scan applied when a scan is suitably performed) Order information) is selected. Alternatively, it is possible to select scan order information according to the attributes (age, disease, etc.) of the subject. Further, it is possible to selectively apply scan order information applied to OCT angiography and scan order information applied to other measurement techniques (for example, three-dimensional scan for acquiring morphological images).

<Image forming unit 220>
The image forming unit 220 forms image data of a cross-sectional image of the fundus oculi Ef based on the sampling result of the detection signal input from the DAQ 130. This processing includes signal processing such as noise removal (noise reduction), filter processing, and FFT (Fast Fourier Transform) as in the case of the conventional swept source OCT. The image data formed by the image forming unit 220 is a group of image data (a group of image data) formed by imaging reflection intensity profiles in a plurality of A lines (lines in the z direction) arranged along the scan line. A scan image data).

  When OCT angiography is performed, the image forming unit 220 performs an angiographic image in which the blood vessels of the fundus oculi Ef are emphasized based on detection data (for example, a detection signal group from the DAQ 130) collected by a predetermined number of scans. (Angiogram). The image forming unit 220 can form an angiographic image in the following manner, for example.

  First, the image forming unit 220 classifies detection data collected by scanning a plurality of lines 300-n (n = 1 to N) a predetermined number of times into time-series data for each line 300-n. For example, when a plurality of lines 300-n (n = 1 to N) are scanned L times, the image forming unit 220 specifies L sets of data corresponding to each line 300-n. Each of the L sets of data includes data collected in one B scan along the line 300-n. L sets of data are collected in the first B scan along the line 300-n, data collected in the second B scan,..., Collected in the Lth B scan. Data. Therefore, L sets of data are time-series data obtained by L B scans executed at different timings.

  Next, the image forming unit 220, based on the time series data of each line 300-n, a two-dimensional angiographic image corresponding to the line 300-n, that is, a B scan plane (longitudinal section) including the line 300-n. An angiographic image representing the surface is formed. This process is performed in the same manner as conventional OCT angiography. For example, the image forming unit 220 first forms a normal OCT image (B-mode image composed of a group of A-scan image data) based on each of the L sets of data. Thereby, L B-mode images corresponding to the line 300-n are obtained. The image forming unit 220 identifies an image area that changes between L B-mode images. This process includes, for example, a process for obtaining a difference between different B-mode images. Each B-mode image is luminance image data representing the form of the eye to be examined, and an image region corresponding to a part other than a blood vessel is considered to be substantially unchanged. On the other hand, considering that the backscattering contributing to the interference signal changes randomly due to blood flow, an image region in which changes occur between the L B-mode images (for example, a pixel whose difference is not zero or the difference is predetermined) It can be estimated that a pixel that is equal to or greater than the threshold is a blood vessel region. The image forming unit 220 gives a predetermined pixel value to the pixels in the specified blood vessel region. This pixel value may be, for example, a relatively high luminance value (expressed bright and white at the time of display) or a pseudo color value. Note that the blood vessel region can also be specified using Doppler OCT or image processing, as in other conventional techniques.

  Accordingly, N two-dimensional angiographic images corresponding to N lines 300-n (n = 1 to N) are obtained. The image forming unit 220 arranges N two-dimensional angiographic images according to the arrangement order m of the N lines 300-n (n = 1 to N). This processing is performed by, for example, converting N two-dimensional angiographic images into a single three-dimensional coordinate in accordance with the arrangement order m and arrangement interval (spacing) of N lines 300-n (n = 1 to N). Includes the process of placing (embedding) in the system. That is, stack data can be formed by rearranging N two-dimensional angiographic images according to the arrangement of N lines 300-n (n = 1 to N). Such stack data is an example of an image (three-dimensional angiographic image) representing a three-dimensional distribution of blood vessels in the fundus oculi Ef.

  As another example of the three-dimensional angiographic image, there is volume data (voxel data) formed by interpolating the stack data. Such volume data is constructed by, for example, a data processing unit 230 described later. The process for forming an angiographic image from the collected detection data is not limited to the above example, and an angiographic image can be formed using any known technique.

  The image forming unit 220 includes, for example, at least one of a processor and a dedicated circuit board. In the present specification, “image data” and “image” based thereon may be identified. Further, the part of the eye E to be examined and the image representing it may be identified.

<Data processing unit 230>
The data processing unit 230 performs image processing and analysis processing on the image formed by the image forming unit 220. For example, the data processing unit 230 executes correction processing such as image luminance correction and dispersion correction. Further, the data processing unit 230 performs image processing and analysis processing on an image (fundus image, anterior eye image, etc.) obtained by the fundus camera unit 2. The data processing unit 230 includes, for example, at least one of a processor and a dedicated circuit board.

  The data processing unit 230 can form a three-dimensional image of the fundus oculi Ef by performing an interpolation process for interpolating pixels between a plurality of tomographic images formed by the image forming unit 220. A three-dimensional image is an image in which pixel positions are defined by a three-dimensional coordinate system. As a three-dimensional image, stack data obtained by three-dimensionally arranging a plurality of tomographic images along a plurality of scan lines based on the positional relationship of the scan lines, or voxels obtained by interpolating stack data, etc. Data (volume data). A display image is formed by performing rendering (volume rendering, MIP (Maximum Intensity Projection), etc.) on the three-dimensional image. In addition, a cross section can be set in a three-dimensional image and displayed (multi-section reconstruction: MPR). In addition, projection data and shadowgrams can be obtained by projecting at least a part of the three-dimensional image in the z direction (A line direction, depth direction).

<User Interface 240>
The user interface 240 includes a display unit 241 and an operation unit 242. The display unit 241 includes the display device 3. The operation unit 242 includes various operation devices and input devices. The user interface 240 may include a device such as a touch panel in which a display function and an operation function are integrated. Embodiments that do not include at least a portion of the user interface 240 can also be constructed. For example, the display device may be an external device connected to the ophthalmologic photographing apparatus.

<Operation>
The operation of the ophthalmologic photographing apparatus 1 will be described. An example of the operation is shown in FIG. In this example, OCT angiography is performed.

(S1: Set scan pattern)
First, an OCT scan pattern of the fundus oculi Ef is set. The scan pattern is manually set using the user interface 240, for example. Alternatively, the main control unit 211 can automatically set the scan pattern based on the scan pattern or disease type applied in the past. Here, scan patterns and disease types applied in the past are acquired with reference to an electronic medical record or the like.

(S2: Select scan order information corresponding to the scan pattern)
The main control unit 211 acquires scan order information corresponding to the scan pattern set in step S1 from the scan information 212a.

(S3: OCT is performed while controlling the optical scanner based on the scan order information)
In response to the OCT start trigger, the main control unit 211 controls the OCT unit 100 and the optical scanner 42 to execute OCT of the fundus oculi Ef. At this time, the main control unit 211 controls the optical scanner 42 based on the scan order information acquired in step S2.

As an example, when the scan order information 212b illustrated in FIG. 4B is selected, the main control unit 211 selects a plurality of lines 300-n (n = 1 to N) included in the raster scan 300 illustrated in FIG. 4A in the scan order. Execute in the order indicated by m ₁ , m ₂ , m ₃ ,..., m _N. Then, this series of scans is repeatedly performed a predetermined number of times (for example, four times). Thereby, scanning along a plurality of lines 300-n (n = 1 to N) is executed a predetermined number of times in an order different from the arrangement order. At this time, the optical scanner 42 is set so that scanning along two or more lines 300-n, 300- (n + 1),..., 300- (n + j) arranged spatially continuously is not continuously performed. Can be controlled. Further, the optical scanner 42 can be controlled so that scanning along two lines 300-n and 300- (n + 1) arranged spatially continuously is performed at a timing separated by a predetermined time interval or more. According to such a scan, lines 300-n to 300- (n + j) (j is an arbitrary integer between 1 and N-1) in which the spatial arrangement is continuous are continuously scanned in time. Can be avoided as much as possible.

When the parameter for changing the interval (spacing) of the N lines 300-n (n = 1 to N) is included in the scan order information 212b, the main control unit 211 determines that the scan order m ₁ , m ₂ , m ₃ ,..., _{M N} and the optical scanner so as to execute a series of scans of the plurality of lines 300-n (n = 1 to N) in the order indicated by the parameters _{N N} and the spacing represented by the parameters. 42 can be controlled. Further, as in a modification example described later, when the scan order information 212b includes a parameter for changing the scan speed (temporal interval), the main control unit 211 scans the scan orders m ₁ , m ₂ , The optical scanner 42 is configured to execute a series of scans of the plurality of lines 300-n (n = 1 to N) in the order indicated by m ₃ ,..., m _N and at the scan speed represented by the parameter. Can be controlled. If both the parameters for changing the spacing and the parameters for changing the scan speed are included in the scan order information 212b, some or all of the scan order, spacing, and scan speed are changed. It is possible to perform control so as to.

  Further, by performing tracking in parallel with the repetition of such a series of scans, it is possible to avoid the shift of the scan position due to the movement of the eye E. Tracking will be described later.

(S4: classify into time-series data for each line)
The image forming unit 220 classifies the detection data collected in step S3 into time series data corresponding to each of a plurality of lines. This process is executed based on, for example, the acquisition order of the detection data sequentially collected by the repeated scan in step S3 and the scan order information selected in step S2.

(S5: forming a two-dimensional angiographic image along each line)
Next, the image forming unit 220 forms a predetermined number (for example, four) of B scan images arranged in time series for each line based on the time series data classified for each line in step S4, and these B scans. A two-dimensional angiographic image for each line is formed based on the image.

(S6: forming a three-dimensional angiographic image)
Subsequently, the image forming unit 220 3 represents the distribution of blood vessels in the scan area (three-dimensional region) of the plurality of lines based on the plurality of two-dimensional angiographic images corresponding to the plurality of lines formed in step S5. A dimensional angiographic image is formed. Further, the data processing unit 230 can form volume data based on the three-dimensional angiographic image (stack data or the like). This volume data is image data expressing the distribution of blood vessels in the scan area using voxels.

Note that when creating a three-dimensional angiographic image from a plurality of two-dimensional angiographic images, the plurality of two-dimensional angiographic images are rearranged. Specifically, the image forming unit 220 (or the data processing unit 230) changes the time-series order of the plurality of two-dimensional angiographic images to the spatial arrangement order of the plurality of lines 300-n based on the scan order information 212b. Reverse conversion. In other words, the inverse transform ^f -1 _(m n) of the transformation f _(n) = _m n for performing a scan = n applies. As described above, since the transformation f is bijective, the inverse transformation f ⁻¹ is uniquely determined.

  The data processing unit 230 can form a volume rendering image, an MPR image, a projection image, and a shadowgram based on a three-dimensional angiographic image (stack data, volume data, etc.). The main control unit 211 causes the display unit 241 to display the image formed in this way, the two-dimensional angiographic image formed in step S2, and the morphological image (normal B-scan image, rendering image, etc.). be able to.

<Action and effect>
The operation and effect of the ophthalmologic photographing apparatus according to the embodiment will be described.

  The ophthalmologic photographing apparatus according to the embodiment is configured to perform optical coherence tomography (OCT) of the fundus using a scan pattern in which a plurality of lines are arranged, and includes a data collection unit, an optical scanner, a control unit, and an image forming unit. . The ophthalmologic imaging apparatus of the embodiment can perform OCT angiography.

  The data collection unit is configured to project measurement light onto the fundus, detect interference light between the return light and the reference light, and collect the detection data. In the present embodiment, elements in the OCT unit 100 and an optical member that forms a measurement arm are included in the data collection unit.

  The optical scanner is configured to be able to deflect measurement light two-dimensionally. In the present embodiment, the optical scanner 42 corresponds to this.

  The control unit controls the optical scanner so that the plurality of lines are scanned a predetermined number of times in an order different from the order of arrangement of the plurality of lines (that is, spatial arrangement order). In the present embodiment, the main control unit 211 corresponds to this. Note that the number of scans may be the same or different for all the plurality of lines.

  The image forming unit forms an angiographic image in which the blood vessels of the fundus are emphasized based on the detection data collected by the data collecting unit while controlling the optical scanner by the control unit. In the present embodiment, the image forming unit 220 (and the data processing unit 230) corresponds to this.

  According to such an embodiment, since scanning of a plurality of lines is configured to be executed in an order different from the order of arrangement, the same line is compared with the conventional technique in which the same line is continuously and repeatedly scanned. The scan time interval can be increased. Thereby, a temporal change in blood flow can be detected with higher sensitivity, and a low-speed blood flow (weak blood flow signal) can also be detected. In addition, since the scan of another line can be executed between different scans of the same line (that is, the scan of another line can be executed during a non-continuous scan of the same line), the imaging time is wasted. There is no end to it.

  Also, according to such a scanning mode, the possibility that the eye to be inspected follows the movement trajectory of the measurement light is reduced as compared with a conventional apparatus that performs scanning according to the spatial arrangement order of a plurality of lines. The

  In the embodiment, the control unit may be configured to control the optical scanner so as to repeat a series of scans in which a plurality of lines are scanned once. According to this configuration, since the scan time interval for the same line can be increased, a weak blood flow signal can be captured with higher sensitivity. Furthermore, the time required for the entire scan can be shortened. In this case, a plurality of lines can be scanned an equal number of times.

  Further, the control unit may be configured to cause the optical scanner to execute the series of scans so as to scan the plurality of lines once in a predetermined order. The predetermined order is determined by, for example, the regular replacement described above.

  In the embodiment, the image forming unit performs a process of classifying the detection data collected by the data collecting unit into time-series data for each of a plurality of lines, and a two-dimensional blood vessel along the line based on each of the time-series data It is configured to execute a process of forming a contrast image and a process of forming a three-dimensional angiographic image by arranging a plurality of two-dimensional angiographic images formed for a plurality of lines in the order of arrangement of the plurality of lines. It may be.

  Note that the image forming unit may be configured to execute other processes and / or execute the processes in another order. For example, the image forming unit may be configured to form a three-dimensional angiographic image from a three-dimensional image (stack data, volume data, etc.) arranged in time series. In addition, a two-dimensional blood vessel image (or a B-scan image arranged in time series, etc.) and the arrangement order of a plurality of lines can be associated and rearranged when displayed. Further, identification information (flag or the like) may be attached to the blood vessel region, and the pixels of the blood vessel region may be emphasized when displayed.

<Modification>
The embodiment described above is merely an example of the present invention. A person who intends to implement the present invention can arbitrarily make modifications (omission, substitution, addition, etc.) within the scope of the present invention.

  As a first modification, tracking can be applied in the above embodiment. The tracking is performed by monitoring the movement of the eye E using an observation image of the fundus oculi Ef, and controlling the optical scanner 42 in real time according to the movement, so that the eye movement, body movement, and pulsation are controlled. This is a technique for canceling the positional shift of the optometry E.

  An observation image of the fundus oculi Ef is acquired by the fundus camera unit 2 (the illumination optical system 10, the imaging optical system 30, etc.). The arithmetic control unit 200 (for example, the data processing unit 230) identifies, for example, at least one feature part of the fundus oculi Ef by analyzing frames sequentially acquired as an observation image having a predetermined frame rate. The characteristic part is, for example, an optic nerve head, a macula, a blood vessel (a characteristic blood vessel, a branching portion of the blood vessel, etc.), a lesioned part, or the like. Furthermore, the arithmetic and control unit 200 obtains the displacement of the characteristic part in the sequentially acquired frames. For example, the arithmetic control unit 200 sequentially calculates the displacement with respect to the characteristic part specified from the first frame. When a single feature part is considered, at least a translation of the feature part (that is, a translation of the fundus oculi Ef) is detected. In addition, when the characteristic part has an asymmetric shape, the rotational movement of the fundus oculi Ef can also be detected. Further, when considering two or more characteristic parts, it is possible to detect parallel movement and rotational movement of the fundus oculi Ef.

  The main control unit 211 controls the optical scanner 42 so as to cancel the displacement obtained by the arithmetic control unit 200. That is, the scan position is shifted by the detected displacement. Thereby, even when the eye E moves during scanning, substantially the same line can be scanned.

  When tracking is applied, for example, the shape and size of the line 300-n are not changed, but the position and / or orientation thereof is adjusted in real time. The amount of offset from the default position and the default direction of the line 300-n is obtained from, for example, time-series changes in the position of the characteristic part of the fundus oculi Ef drawn in the observation image.

  A second modification will be described. In the above embodiment, the control unit 210 (or 210A) performs the first mode in which OCT is performed according to the arrangement order (spatial arrangement order) of the plurality of lines included in the scan pattern, and the arrangement order of the plurality of lines. The optical scanner 42 may be controlled by selecting a second mode in which OCT is performed in a different order (time-series order). For example, the mode can be selected according to the age of the subject, the situation in the past examination, the measurement technique, and the like. The mode is selected by the user or the control unit 210 (210A).

  Further, the control unit 210 (210A) may be configured to select the first mode or the second mode according to the region of the fundus oculi Ef on which OCT is performed. For example, when the scan area is set in the center region of the fundus (for example, when the scan area includes macula), the second mode in which an order different from the arrangement order of the plurality of lines is applied is selected, and the scan area However, it is possible to select the first mode in which the arrangement order of a plurality of lines is applied as it is to the fundus peripheral region (for example, when the scan area does not include macular).

  A third modification will be described. In the above embodiment, the case where the scan order of the plurality of lines 300-n (n = 1 to N) is changed has been described. In addition to the change in the scan order, the scan density (spatial interval) and It is also possible to apply a change in speed (time interval). For example, when scanning a plurality of lines 300-n (n = 1 to N) in an arbitrary order, the initial scan speed is increased, the intermediate scan speed is decreased, and the final scan speed is increased. It is possible to perform control so that sampling on the detection side is executed at a constant speed. Thereby, it is possible to scan relatively important parts at high density. In particular, it is possible to adjust the scan density for a site of interest such as a diseased site or the periphery of the optic disc. Such a control is not limited to a scan including a plurality of lines 300-n (n = 1 to N) extending in the horizontal direction as shown in FIG. 4A, but also a scan including a plurality of lines arranged in the vertical direction or concentric circles. The present invention can also be applied to an arbitrary scan pattern such as a scan including a plurality of arranged circles.

DESCRIPTION OF SYMBOLS 1 Ophthalmic imaging device 42 Optical scanner 100 OCT unit 210 Control part 220 Image formation part 230 Data processing part

Claims (5)

An ophthalmologic imaging apparatus capable of performing optical coherence tomography (OCT) of the fundus with a scan pattern in which a plurality of lines are arranged,
Projecting measurement light onto the fundus, detecting interference light between the return light and the reference light, and a data collection unit for collecting the detection data;
An optical scanner capable of two-dimensionally deflecting the measurement light;
A controller that controls the optical scanner to scan the plurality of lines a predetermined number of times in an order different from the arrangement order of the plurality of lines;
An ophthalmologic imaging apparatus comprising: an image forming unit that forms an angiographic image in which blood vessels of the fundus are emphasized based on detection data collected by the data collecting unit while controlling the optical scanner by the control unit. The ophthalmic imaging apparatus according to claim 1, wherein the control unit controls the optical scanner so as to repeat a series of scans in which the plurality of lines are scanned once. The ophthalmic imaging apparatus according to claim 2, wherein the control unit causes the optical scanner to execute the series of scans so as to scan the plurality of lines once in a predetermined order. The image forming unit classifies the detection data collected by the data collection unit into time-series data for each of the plurality of lines, and based on each of the time-series data, a two-dimensional angiographic image along the line And forming a three-dimensional angiographic image by arranging a plurality of two-dimensional angiographic images formed for the plurality of lines in the arrangement order. Ophthalmic photography device. A displacement detector for detecting the displacement of the fundus;
The ophthalmologic imaging apparatus according to claim 1, wherein the control unit controls the optical scanner so as to cancel the displacement detected by the detection unit.