JP2018068630A - Tomographic image acquisition apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the following problem: examining the vascular structure and photoreceptor cell morphological distribution in a wide range of a retina with AO-OCT is time-consuming and troublesome, and thus the burden on the patient becomes large.SOLUTION: A tomographic image acquisition apparatus according to the present invention includes: first specification means for specifying a first position at which to acquire a low-resolution tomographic image in a fundus image of a subject eye; first acquisition means for acquiring a low-resolution tomographic image corresponding to the first position; second specification means for specifying a second position at which to acquire a high-resolution tomographic image in the low-resolution tomographic image; and second acquisition means for acquiring a high-resolution tomographic image based on the first position and the second position.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a tomographic image acquisition apparatus and method, and more particularly to a tomographic image acquisition apparatus and method that can efficiently acquire a high-resolution tomographic image.

  2. Description of the Related Art In recent years, a tomographic imaging apparatus (Optical Coherence Tomography: hereinafter referred to as OCT) using interference by low coherence light has been put into practical use as an ophthalmic examination apparatus. Further, AO-OCT which is equipped with an adaptive optical system (adaptive optics: hereinafter referred to as AO) and renders a fine structure of the retina with high resolution has been researched and developed (Non-patent Document 1).

  The optical system of the human eyeball (cornea, crystalline lens, vitreous body) is non-uniform, and when photographing the fundus, aberration occurs in the light wavefront of the light that images the fundus, so the fundus retina is photographed with high resolution. That is generally difficult. In AO-OCT, the aberration of the optical wavefront is measured using a wavefront sensor, and the aberration of the optical wavefront is canceled using a wavefront correction device. Therefore, a high-resolution fundus image can be acquired.

  The aberration received by the light wavefront transmitted through the eyeball depends on the incident angle to the pupil, and the angle at which the aberration can be regarded as almost constant with respect to the incident angle is within several degrees (corresponding to 1 mm or less in length on the retina). It is said. Aberration correction by the wavefront correction device is difficult to switch at high speed according to the incident angle of the imaging light to the pupil position. Therefore, the OCT imaging angle of view using AO is limited to several degrees, and the conventional OCT The field angle of view is limited to a narrow range compared to the angle of view (10 mm or more). In addition, since the angle of view is narrow and characteristic structures of the fundus (such as blood vessel bifurcation and optic nerve head) cannot be photographed at the same time, the fundus photographing position can be identified only with a high-resolution tomographic image photographed using AO. It was sometimes difficult.

  Further, in AO-OCT, it is necessary to increase the numerical aperture (Numerical Aperture: hereinafter referred to as NA) as compared with conventional OCT, and the depth of focus becomes shallow. For this reason, it is necessary to set the step of the focus position more finely than the conventional OCT (Patent Documents 1 and 2) in which a plurality of striped images taken at different focus positions are combined.

JP 2010-169503 JP2012-213449

“Adaptive opticals optical coherence tomography for high-resolution and high-speed 3D retina in vivo imaging”, R.A. Zawadzki et. al, Optics Express, Vol. 13, pp. 8532-8546

  As described above, AO-OCT has a narrow angle of view and a shallow depth of focus, so it takes time and effort to examine the vascular structure in a wide range including the retinal plane and the depth direction and the morphological distribution of photoreceptor cells. There was a problem of increasing the burden. In addition, there is a problem that it is difficult to identify the photographing position of the photographed high-resolution tomographic image.

  Therefore, there is a demand for an imaging apparatus capable of efficiently performing imaging that can depict the blood vessel structure of the retina and the anatomical structure / lesion.

  In view of the above problems, an object of the present invention is to provide a tomographic image acquisition apparatus that can easily specify the acquisition position of a high-resolution tomographic image by using a low-resolution tomographic image.

  It is another object of the present invention to provide a tomographic image acquisition apparatus that displays an acquisition position of a high-resolution tomographic image in an easy-to-understand manner.

  A tomographic image acquisition apparatus according to the present invention includes a first specifying means for specifying a first position for acquiring a low-resolution tomographic image in a fundus image of an eye to be examined, and a low-resolution image corresponding to the first position. First acquisition means for acquiring a tomographic image; second specifying means for specifying a second position at which a high-resolution tomographic image is acquired using the resolution tomographic image; the first position; And a second acquisition means for acquiring a high-resolution tomographic image based on the position of.

  The tomographic image acquisition apparatus according to the present invention includes a first display area that displays a high-resolution tomographic image, a second display area that displays a low-resolution tomographic image, and a third display that displays a planar image. Display means having a display area, and corresponding positions of the high-resolution tomographic image displayed in the first display area, the low-resolution tomographic image displayed in the second display area and the third And a control means for displaying each on the planar image displayed in the display area.

  According to the present invention, it is possible to easily specify the acquisition position of a high-resolution tomographic image by using a low-resolution tomographic image.

  Furthermore, according to the present invention, the acquisition position of a high-resolution tomographic image can be displayed in an easy-to-understand manner.

1 is a schematic configuration diagram of an ophthalmologic photographing apparatus according to an embodiment of the present invention. It is a block diagram of the optical system in one Embodiment of this invention. It is a flowchart of the production | generation process of an OCT image. It is a schematic explanatory drawing of the display form by the display control part in one Embodiment of this invention. 6 is a flowchart of a shooting operation according to an embodiment of the present invention. It is a figure which shows an example of the segmentation of a tomographic image. It is a figure for demonstrating the imaging | photography order and the imaging | photography number in one Example of this invention.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to these.

[Example 1]
[Overall configuration of ophthalmic imaging apparatus]
FIG. 1 is a schematic configuration diagram of an ophthalmologic imaging apparatus as a tomographic image acquisition apparatus according to an embodiment of the present invention.

In FIG. 1, the ophthalmologic photographing apparatus includes an optical system 100, a control unit 300, an image generation unit 400, and a display control unit 500. The optical system 100 controlled by the control unit 300 irradiates the test eye 118 with measurement light and detects return light from the test eye 118. The image generation unit 400 receives an electrical signal corresponding to the return light from the optical system 100, processes it to generate a tomographic image T _OCT, and outputs it to the display control unit 500. The display control unit 500 includes a display device such as a liquid crystal display, and displays an input image. The generated image is stored in the storage unit 600 together with information for specifying the eye 118 to be examined.

  The ophthalmologic photographing apparatus shown in FIG. 1 can be realized by a PC (personal computer) connected to hardware having a specific function. For example, the optical system 100 can be realized by hardware, and the control unit 300, the image generation unit 400, and the display control unit 500 can be realized by software modules that can be mounted on a PC connected to the hardware. In the following embodiment, the function is realized by the arithmetic processing unit CPU of the PC executing the software module, but the present invention is not limited to such a method. The image generation unit 400 may be realized by dedicated hardware such as an ASIC, for example, and the display control unit 500 may be a dedicated processor such as a GPU different from the CPU. Further, the connection between the optical system 100 and the PC can be realized by changing the configuration via the network without changing the gist of the present invention.

  Next, a detailed configuration of each unit will be described.

<Configuration of optical system 100>
Hereinafter, the configuration of the optical system 100 will be described with reference to FIG. The main components of the optical system 100 include a light source 101, an AO and measurement unit 140, a reference optical system 150, a light receiving optical system 160, an anterior ocular segment observation unit 170, a fixation lamp optical system 180, and an SLO unit 190. Unless otherwise specified, each unit operates under the control of the control unit 300.

  The light source 101 is a low-coherence light source, for example, a super luminescent diode (hereinafter, SLD) light source having a center wavelength of 840 nm and a wavelength width of 100 nm. In the present embodiment, an SLD light source is used, but a titanium sapphire laser or the like may be used.

  Light emitted from the light source 101 is guided to a beam splitter 103 via a single mode fiber (hereinafter referred to as SM fiber) 102-1, and is branched into measurement light and reference light. In the present embodiment, the beam splitter 103 is configured by a fiber coupler. The branching ratio of the beam splitter 103 is 90 (reference light): 10 (measurement light).

  The branched measurement light is guided to the AO and measurement unit 140 via the SM fiber 102-4, converted into parallel light by the collimator 105-1, and incident on the beam diameter variable unit 141.

  The beam diameter varying unit 141 is a unit that changes the beam diameter of the measurement light and changes the NA that irradiates the fundus Er of the eye 118 to be examined. In the present embodiment, the plurality of lenses are configured to be insertable / removable at adjustable positions. The beam diameter variable unit 141 is configured to be able to communicate with the control unit 300, and can change the beam diameter according to an instruction from the control unit 300. This makes it possible to switch between an OCT mode for imaging with the same resolution as that of normal OCT and an AO-OCT mode for imaging with high resolution. In the OCT mode, imaging is performed with a narrow beam diameter and a low NA, and in the AO-OCT mode, imaging is performed with a wide beam diameter and a high NA. In the OCT mode, it is desirable to set the beam diameter so as to be 2 mm or less on the pupil of the eye 118 to be examined, and to operate the beam diameter variable unit 141 so that the beam diameter is 6 mm or more in the AO-OCT mode. However, since the pupil of the eye 118 does not open to 6 mm or more, or the entrance pupil of the eye 118 is narrow due to a cataract disease or the like, AO-OCT can be imaged with a beam diameter between 2 mm and 6 mm. Various shooting modes may be provided. In the present embodiment, the beam diameter is 1 mm (spot diameter on the fundus of 20 μm) in the OCT mode, and the beam diameter is 6 mm (spot diameter on the fundus of 3.5 μm) in the AO-OCT mode.

  Next, the measurement light passes through the light splitting unit 107 and is guided to the wavefront correction device 104, the scan optical system 108, and the eye 118 to be examined by the relay optical elements 130-1 to 130-6. In this embodiment, the relay optical element is configured by a lens. The relay optical elements 130-1 to 130-6 are adjusted so that the entrance pupils of the wavefront correction device 104, the scan optical system 108, and the eye 118 to be examined are substantially phase conjugate.

  The scanning optical system 108 can perform xy two-dimensional scanning, and may be a scanner that performs two-dimensional scanning with a single mirror, or may be configured by a plurality of scanners. In this embodiment, both the y (vertical) direction and the x (horizontal) direction are galvano scanners. Further, the scanning optical system 108 can change (steer) the photographing position based on an instruction from the control unit 300.

  The relay optical elements 130-5 and 130-6 have a function of adjusting the focus position of the measurement light on the fundus oculi Er. The relay optical element 130-6 is fixed on the stage 109, and the focus position can be adjusted by moving in the optical axis direction. In this embodiment, the focus position is adjusted by moving the lens. However, a Badal Optometer having a mechanism for fixing the lens and adjusting the optical path length may be used.

  The relay optical elements 130-1 to 130-6 may be configured to use a mirror or the like in order to prevent the reflected light from the lens surface from becoming stray light.

  The scanning optical system 108 and the stage 109 are controlled by the control unit 300 and can scan the measurement light in a desired range of the fundus Er of the eye 118 to be examined. The measurement light is incident on the eye 118 to be examined by the movement of the focus lens 116 mounted on the stage 109 in the optical axis direction, and is focused at a desired depth position on the fundus Er.

  The measurement light irradiated on the fundus Er is reflected / scattered to become return light, traces the relay optical elements 130-1 to 130-6 in the reverse order, and returns to the light splitting unit 107. The return light is partly divided by the light splitting unit 107 and guided to the wavefront sensor 106 via the relay optical elements 130-7 and 130-8 and the aperture 132. The relay optical elements 130-7 and 130-8 are adjusted so as to be substantially phase conjugate with the wavefront correction device 104, the scan optical system 108, and the entrance pupil of the eye 118 to be examined. The aperture 132 is inserted to prevent stray light from entering the wavefront sensor 106. Further, the branching ratio of the light splitting unit 107 is determined by the amount of light incident on the eye 117 to be examined, the light usage efficiency (throughput) of the AO and measuring unit 140, the sensitivity of the wavefront sensor 106, and the throughput of the light receiving optical system 160. In form, 90 (transmission): 10 (reflection).

  The return light of the measurement light transmitted through the light splitting unit 107 is incident on the beam splitter 103 via the beam diameter varying unit 141, the collimator 105-1, and the SM fiber 102-4.

  On the other hand, the reference light branched by the beam splitter 103 is emitted through the SM fiber 102-3 and converted into parallel light by the collimator 151. The reference light is reflected by the mirror 153 through the dispersion compensation glass 152. The mirror 153 is disposed on the stage 154 and is driven in the optical axis direction corresponding to the difference in the eye axis length of the subject to adjust the coherence gate position (the optical path length difference between the measurement light and the reference light). Control is performed by the controller 300 as described above. In the present embodiment, the optical path length of the reference light is changed, but it is sufficient that the optical path length difference between the optical path of the measurement light and the optical path of the reference light can be changed.

  The reference light reflected by the mirror 153 follows the optical path in reverse order and enters the beam splitter 103 via the dispersion compensation glass 152, the collimator 151, and the SM fiber 102-3. In the beam splitter 103, the return light of the measurement light and the reference light are combined to become interference light and enter the light receiving optical system 160.

The interference light that has entered the light receiving optical system 160 enters the detector 164 via the collimator 161, the grating 162, and the imaging lens 163. The interference light is decomposed into a spectrum by the grating 162, received for each spectral component of the interference light on the detector 164, converted into a signal S _OCT and input to the image generation unit 400.

<AO operation>
The operation of AO in the AO-OCT mode will be described below.

  In this embodiment, a Shack-Hartmann sensor is used as the wavefront sensor 106. The Shack-Hartmann sensor divides the light incident on the microlens array (in this embodiment, the divided light of the return light of the measurement light) and collects the divided measurement light on the two-dimensional sensor. When the signal of the two-dimensional sensor is imaged, it becomes an image in which condensing points are arranged, and this is called a Hartmann image. The wavefront sensor 106 is connected to the control unit 300, reads the Hartmann image by the control unit 300, and returns aberration of the measurement light based on the amount of movement from the reference point for each condensing point (occurred in the eye to be examined) Aberration).

  The control unit 300 calculates an input signal (drive signal for canceling the aberration) to the wavefront correction device 104 based on the obtained aberration, and drives the wavefront correction device 104 so that the aberration is reduced. A series of operations of acquiring the Hartmann image by the wavefront sensor 106, calculating the aberration in the control unit 300, and driving the wavefront correction device 104 is repeatedly performed, and always moves so that the aberration of the return light of the measurement light is reduced. to continue. In addition, the input signal to the wavefront correction device 104 by the control unit 300 transforms the optical wavefront of the return light of the measurement light into a desired shape, such as a concave shape (defocus) for changing the focus on the fundus Er. It is also possible to superimpose a signal for making it happen.

<Anterior segment observation>
The eye 118 is irradiated with illumination light from the anterior illumination light source 172, and the anterior eye portion of the eye 118 is imaged by the anterior eye observation unit 170. In this embodiment, an LED having a central wavelength of 740 nm is used as the anterior segment illumination light source 172. The illumination light of the anterior segment illumination light source 172 is reflected by the dichroic mirrors 120-1 and 120-2 and enters the anterior segment observation unit 170. The anterior ocular segment observation unit 170 includes an imaging lens 171 and a two-dimensional imaging device 172, and is adjusted so that the anterior ocular segment of the eye 118 to be examined is captured. A signal from the two-dimensional imaging device 172 is input to the display control unit 500 via the control unit 300 and displayed on the display device. In order to facilitate alignment of the eye 118 along the optical axis, a split prism may be introduced into the anterior eye observation unit 170.

  The user turns on the anterior ocular segment illumination light source 172 before starting the OCT imaging, and performs alignment of the eye to be examined 118 using the obtained anterior ocular segment image. Further, if necessary, OCT imaging may be interrupted, the anterior segment illumination light source 172 may be turned on, and the position of the eye 118 to be examined may be confirmed. When the alignment is completed, the anterior ocular segment illumination light source 172 is turned off and imaging by the anterior ocular segment observation unit 170 is completed.

<Fixed light optical system>
The fixation lamp optical system 180 includes an optical element 181 and a light emitting organic EL display module 182. As the display module 182, a liquid crystal, an LED array, or the like can be used.

  A pattern that is lit and displayed on the display module 182 according to an instruction from the control unit 300 is projected onto the fundus Er at an appropriate magnification via the optical element 181 and the dichroic mirrors 120-3, 120-2, and 120-1. By changing the lighting position of the pattern, it is possible to guide the fixation of the eye 118 to be examined and adjust so that a desired position of the fundus Er can be photographed. As the pattern, a cross, a circle, a square, or the like can be used, and it is desirable to use a pattern that can be easily perceived by the eye 118 to be examined. Further, the pattern size may be changed or a color filter may be inserted so that the eye 118 can be easily perceived.

  The optical element 181 can adjust the focus on the fundus oculi Er according to an instruction from the control unit 300. The optical element 181 is placed on the stage 183 and moved in conjunction with the stage 109 of the AO and measurement unit 140.

<SLO part>
The SLO unit 190 captures an image in a wide range of the fundus oculi Er (angle of view: about 40 degrees × 40 degrees). The SLO unit 191 includes a light source, a two-dimensional scanner, a detector, and the like, and acquires about 15 SLO images per second. The SLO signal S _SLO acquired by the SLO unit 191 is converted into an SLO image M _SLO by the image generation unit 400, and then input to the display control unit 500 and displayed on a display device included in the display control unit 500. .

  The acquired SLO image can be used for confirming an imaging position of a diseased part or the like, or for specifying an imaging position using an input device such as a keyboard or a mouse (not shown).

<Tracking>
The optical system 100 detects a shift of the photographing position due to fixation fine movement of the eye 118 to be examined, and performs tracking for adjusting the photographing position in real time. The procedure will be described below.

  One of the SLO images of the fundus Er acquired by the SLO unit 191 is selected as a reference image and stored in the storage unit 600. It is desirable that the reference image has a high signal-to-noise ratio (hereinafter referred to as S / N ratio) and little image distortion, and an averaged image of a plurality of SLO images may be used.

  When imaging is started by the SLO unit 191, the acquired SLO image is sent to the control unit 300, and the amount of positional deviation is obtained based on the calculation result of the correlation value with the reference image. For the calculation of the correlation value, the correlation value may be calculated while the pixels of the reference image and the SLO image are relatively shifted, or a Phase Only Correlation (POC) method using Fourier transform may be used. In order to calculate at high speed, an FPGA unit or a GPU unit may be used.

  Based on the amount of displacement obtained by the calculation, the control unit 300 sends an instruction for canceling the displacement to the scanning optical system 108, and the galvano scanner in the x direction and the galvano scanner in the y direction are driven to photograph the fundus Er. The position is adjusted.

  Since tracking is based on an SLO image in which a wide area of the fundus oculi Er is captured, the amount of positional deviation can be obtained even when the photographing position is greatly deviated, and the same position can be stably photographed without being out of frame. is there.

<Control unit 300>
Next, the control unit 300 will be described. As described above, in the present embodiment, the control unit 300 realizes its function when the CPU executes a software module, controls each unit of the optical system 100, and controls the operation of the entire ophthalmologic photographing apparatus according to the present invention. . The control unit 300 also accepts input from a user who operates the ophthalmologic photographing apparatus. Specifically, information such as a patient ID for specifying an eye to be examined, parameters necessary for imaging, selection of a pattern for scanning the fundus, and the like are input to the control unit 300 from a device such as a keyboard or a mouse (not shown). Based on this, the control unit 300 has a function of controlling each unit and storing the obtained data such as signals and images in the storage unit 600.

<Image Generation Unit 400>
The image generation unit 400 generates and outputs an image related to the eye to be examined by performing various processes on the signal output from the optical system 100.

The generation of the OCT image, as shown in FIG. 3, remaps of wavenumber signals _{S OCT} respect to wavelength at the step S301, after removing the DC component in step S302, OCT image _{T OCT} by the Fourier transform at step S302 To get. In addition, alignment and averaging of a plurality of OCT images, and processing for generating a three-dimensional OCT image V _OCT by combining images taken at a plurality of different fundus positions are performed.

In the generation of the SLO image, a process of converting the signal S _SLO into two-dimensional data in synchronization with the signal of the scanner and converting it into the SLO image M _SLO is performed.

<Display control unit 500>
Next, the display control unit 500 will be described. As described above, the display control unit 500 includes a display device such as a liquid crystal display, and displays an image input from the image generation unit 400. FIG. 4 shows the configuration of the screen displayed by the display control unit 500. In addition to the screen shown in FIG. 4, an input screen for specific information of the eye to be examined such as a patient ID input by the control unit 300 is necessary. Since it is not a central part, description is omitted.

  In FIG. 4, the display device 401 displays a screen including an image display area 402 and a display area 403 for eye information to be examined. In the eye information display area 403, information such as patient ID, name, and age is displayed. The image display area 402 includes image display areas 404, 405, 406, 407, and 408, buttons 420, 421, 422, sliders 412, 431, 432, and pull-down menus 413 that are user interfaces that can be operated by the user. Has been.

  The image displayed in each display area and the function of the user interface will be described in the flow of the photographing operation described later.

[Shooting operation]
Next, the operation of the ophthalmologic photographing apparatus according to the embodiment of the present invention will be described with reference to the flowchart shown in FIG.

<Step S501> (SLO, OCT operation start)
The operation of the light source, the scanner unit, and the like of the SLO unit 191 is started, and the fundus Er of the eye to be examined 118 is irradiated two-dimensionally with light. A preview of the SLO image is displayed in the image display area 404, and the photographing position and image quality of the fundus oculi Er can be confirmed.

  Also, the operation of the light source 101 and the scanning optical system 108 is started. The wavefront correction device 104 performs initialization so that the reflection surface becomes flat. A preview of the OCT image is displayed in the image display area 405.

<Step S502> (Reference SLO Image Acquisition)
The SLO unit 191 and the fixation lamp optical system 180 are adjusted so that a desired photographing position of the fundus Er is acquired. The lighting position of the fixation lamp optical system 180 is fixed, and a desired shooting position is shot by the steering of the SLO unit 191.

  Next, the focus position of the SLO is adjusted. The focus position can be adjusted automatically or manually, and the user can select either. In the automatic adjustment of the focus position, the control unit 300 moves the SLO focus position by driving, and adjusts the focus position so that the root mean square (hereinafter referred to as rms) value of the SLO image becomes maximum.

  The SLO image acquired after the focus adjustment is completed is set as a reference SLO image and stored in the storage unit 600 together with the rms value. In manual focus position adjustment, the control unit 300 is driven to move the focus position of the SLO based on a value designated by the user with the slider 431. An SLO image acquired after it is determined that there is no input from the user at a preset time is set as a reference SLO image and is stored in the storage unit 600 together with the rms value. When the reference image is already stored in the storage unit 600, the newly acquired rms value is compared with the stored rms value, and the reference SLO image having a high rms value is stored together with the rms value. Is remembered.

  The OCT focus is interlocked with the SLO focus, and the control unit 300 moves and drives the stage 109 in accordance with the adjustment of the SLO focus position.

<Step S503> (Start tracking)
Tracking is started using the reference SLO image acquired in step S502 as a reference image.

<Step S504> (OCT imaging position (x, y) designation)
A rectangular mark 410 indicating the OCT imaging position is superimposed on the image display area 404, and the user designates the imaging position (rectangular area) by moving the mark 410 with an input device such as a mouse. The control unit 300 drives the scan optical system based on the position of the mark 410 and performs pre-scan within the imaging range specified by the mark 410. Pre-scanning is performed by reducing the number of OCT images acquired in one two-dimensional scan. In this embodiment, an OCT image at the center of the imaging range is acquired and displayed in a preview in the display area 405. Further, the control unit 300 drives the stage 154 based on the luminance value of the OCT image, and adjusts the coherent gate position so that the retinal tomography of the fundus Er is within the image.

  In the present embodiment, a single OCT image is preview-displayed, but a plurality of OCT images may be previewed. For example, by displaying an OCT image of the outer periphery of the imaging range designated by the mark 410 or the center cross, it is possible to determine whether the focus and coherent gate adjustment are appropriate. The user can also finely adjust the coherent gate manually by operating the slider 432.

<Step S505> (OCT image acquisition)
When the user presses the button 420, acquisition of the three-dimensional OCT data is started. Data is acquired for an imaging range designated by the mark 410 based on preset parameters such as pixel resolution, speed, and number of acquisitions.

<Step S506> (Segmentation execution)
The data acquired in step S505 is sent to the image generation unit 400 to be imaged and displayed in the display area 405. Further, segmentation (part information acquisition) is performed, and the superposition of the segmentation lines can be switched between display / non-display.

  Here, the segmentation of the retina will be specifically described.

  The image generation unit 400 creates an image by applying a median filter and a Sobel filter to the tomographic image to be processed extracted from the OCT image (hereinafter referred to as a median image and a Sobel image, respectively). Next, a profile is created for each A scan from the created median image and Sobel image. The median image has a luminance value profile, and the Sobel image has a gradient profile. Then, a peak in the profile created from the Sobel image is detected. By referring to the profile of the median image before and after the detected peak and between the peaks, the boundary of each region of the retinal layer is extracted.

  The segmentation result will be described with reference to FIG. FIG. 6 is a luminance averaged tomographic image, and shows that the segmentation lines are superimposed with solid lines. The segmentation detects 6 layers in the present embodiment. The breakdown of the six layers is as follows: (1) nerve fiber layer (NFL), (2) ganglion cell layer (GCL) + inner plexus layer (IPL) combined layer, (3) inner granule layer (INL) + outer reticular shape Layer (OPL) combined layer, (4) Outer granule layer (ONL) + Outer boundary membrane (ELM) combined layer, (5) Ellipoid Zone (EZ) + Interchange Zone (IZ) + Retinal pigment epithelium (RPE) (6) Choroid.

  Note that the segmentation described in this embodiment is an example, and other methods such as segmentation using the Dijkstra method may be used. The number of layers to be detected can be arbitrarily selected.

<Step S507> (AO-OCT imaging position designation)
Dashed lines 411-1 and 411-2 superimposed on the image in the display area 405 are drawn along the x and y directions of the three-dimensional OCT image, and the positions of the broken lines can be adjusted by the sliders 412-1 and 412-2. It is. When the value indicated by the slider 412 is updated, the tomographic image at the position corresponding to the broken line 411 is displayed in the display area 406 (corresponding to the horizontal direction H: 411-2), 407 (vertical direction V: 411-1). Automatically). The user adjusts using the slider 412 so that the AO-OCT imaging position is included. In addition, the layers separated by the segmentation from the pull-down menu 413 can be selected singly or in combination, and the desired retinal layer is highlighted and displayed, such as making the non-selected layer transparent or translucent, The photographing position is easily adjusted.

  Note that the range for drawing the tomographic image may be narrowed to about 1 mm from the position where the broken lines 411-1 and 411-2 intersect so that the AO-OCT imaging position can be easily specified. Moreover, the broken lines 411-1 and 411-2 may be projected along the curvature of the retina so that the position of the tomographic image can be specified more easily. Furthermore, the broken lines 411-1 and 411-2 may be configured so that an arbitrary direction can be designated with an input device such as a mouse, and a tomographic image generated from a three-dimensional OCT image by interpolation or the like is displayed in the display area. You may be comprised so that a disease site | part etc. can be designated easily.

  AO-OCT imaging position designation is performed by the user moving a rectangular mark 413 displayed superimposed on the display area 406 or the display area 407. This mark 413 is displayed in accordance with the position where the broken lines 411-1 and 411-2 intersect in the display area (either 406 or 407) where the mouse cursor operated by the user is entered. In addition, the user shifts to the AO-OCT mode by pressing a button 421 for switching between the OCT mode and the AO-OCT mode.

  When shifting to the AO-OCT mode, the control unit 300 drives the beam diameter variable unit 141 to change the beam diameter, and starts the AO operation. The control unit 300 performs preview shooting in the AO-OCT mode based on preset parameters such as scan amplitude and scan speed. In the present embodiment, the center imaging position of the area designated by the mark 413 is imaged, and an AO-OCT image is previewed on the display area 408. Here, generation of an AO-OCT image will be described. Similar to a normal OCT image, an A-scan tomographic image is obtained by performing FFT conversion on a signal corresponding to interference light. A depth position in the OCT image is set based on the set focus position. An OCT image having a width (width in the height direction of the image) corresponding to the width of the high resolution region in the retinal depth direction of the tomographic image, centered on the position corresponding to the set depth position of the A-scan tomographic image. Extracted as a high-resolution tomographic image. An AO-OCT image is generated by repeating this process for A scan corresponding to the horizontal width of the image.

  Based on the shooting range designated by the mark 413, the lighting position of the fixation lamp optical system 180 and the moving distance of the shooting position by the steering (hereinafter referred to as the steering amount) are calculated, and the control unit 300 automatically adjusts the shooting position. I do. In the present embodiment, the lighting position of the fixation lamp is set according to the intersection of the broken lines 411-1 and 411-2. In addition, the focus position at the time of AO-OCT imaging is based on the coherence gate position at the time of OCT imaging (upper end of the image) and the highly reflective layer of the retina (at least one of the optic nerve fiber layer, IS / OS, RPE, etc.) It is assumed that the focus position is set to a position where the position of the mark 413 is obtained from the relative position between the two. In addition, the focus position can be adjusted by superimposing a preset defocus on the wavefront correction device 104 with the highly reflective layer as a reference. In order to determine the reference, through focus shooting (shooting continuously performed in the depth direction) may be performed after the start of shooting. Alternatively, the setting value of the stage 109 that is in focus on the highly reflective layer and the defocus of the wavefront correction device 104 may be stored in the storage unit 600 in advance, and the control unit 300 may be operated based on the stored value.

  If it is not possible to automatically move to a desired photographing position, such as when fixation guidance is not successful, it is possible to manually adjust the lighting position of the fixation lamp and the steering amount. When the alignment of the eye to be examined 118 is shifted due to the adjustment of the imaging position or the like, a configuration that prompts the readjustment of the alignment may be provided.

  The lighting position and steering amount of the fixation lamp optical system 180 are stored in the storage unit 600, and when the same position is re-photographed, the control unit 300 is operated based on the stored lighting position and steering amount. In addition, in order to correct the shift of the shooting position that is automatically adjusted with the designation of the shooting position, the lighting position and the steering amount may be adjusted based on the manually adjusted lighting position and steering amount.

  When the lighting position of the fixation lamp optical system 180 is changed, the reference SLO image is shifted from the reference position, so that the tracking is temporarily interrupted.

  The shooting range (the size of the rectangular area) designated by the mark 413 can be arbitrarily set by the user. However, since the angle of view is limited in shooting using AO, the fundus area is divided when shooting a wide range. Data needs to be acquired. For this reason, the size of the mark 413 that can be specified by the user has different upper limit values in the x, y direction and the depth direction. When the user tries to specify a value exceeding the upper limit value, the size of the mark 413 is automatically set to the upper limit value, or a prompt screen notifying the occurrence of an error is displayed.

<Step S508> (AO-OCT imaging start)
The user presses the button 422 to start AO-OCT imaging. If it is determined in step S507 that the mode has not shifted to the AO-OCT mode, the control unit 300 drives the beam diameter variable unit 141 to change the beam diameter, and starts the AO operation.

  First, based on the imaging range designated by the mark 413, the control unit 300 determines parameters such as the scan amplitude and scan speed of the scan optical system 108, the number of images to be imaged, and the imaging order.

  When the imaging range exceeds the maximum width of a single AO-OCT image, the imaging region is divided so that AO-OCT images at adjacent imaging positions overlap. Taking into account the shallow depth of focus (theoretically about 20 μm) in the depth direction, the image is divided into regions of about 50 μm to 100 μm. The reason why the larger area than the theoretical value is set is that the change in focus is moderate even outside the range of the depth of focus. However, it is possible to divide the area into 100 μm or more in order to shorten the photographing time.

  When tracking is interrupted in step S507, or when shooting is performed by changing the lighting position of the fixation lamp optical system 180 a plurality of times, a reference SLO image is acquired before the start of AO-OCT shooting, and tracking is performed. To start.

  The imaging sequence in the AO-OCT mode according to the present embodiment will be described with reference to FIG.

  In FIG. 7, a region (for example, region 702) indicated by a solid line superimposed on the OCT image 701 is an imaging range in which aberrations can be regarded as substantially constant, and the lighting position, steering amount, and focus position of the fixation lamp optical system 180. The area that can be photographed without changing is shown.

  FIG. 7A shows a case where the shooting range designated by the user is narrow. By adjusting the fixation guidance, steering, and focus position so that the region 703 includes the mark 413, an AO-OCT image can be acquired by one imaging.

  FIGS. 7B and 7C show a case where the shooting range specified by the user is wide and the entire specified range cannot be included in a single shooting. In particular, it is necessary to take images while moving both in the retina plane direction and in the depth direction. In this case, in order to reduce the amount of change in the aberration to be corrected, priority is given to the adjustment of the focus position, and the shooting order is determined so as to continuously shoot in the depth direction. In addition, since it is difficult for an alignment shift to occur, it is possible to perform photographing efficiently.

  FIG. 7B shows an example in which the range designated by the mark 413 is taken by dividing the range into four. After photographing the area 703-1, the focus position is moved to photograph the area 703-2. Next, steering is performed to capture the area 703-3, and finally the focus position is moved to capture the area 704-4.

  In FIG. 7 (c), the area 704-1 at the center of the mark 413 is first imaged, and then the areas 704-2 to 704-5 are imaged. An area 704-1 is used as a reference image for creating a composite image. The creation of the composite image will be described in step S514 described later.

<Step S509> (Fixation guidance / steering)
Based on the imaging order determined in step S508, the control unit 300 operates the fixation lamp optical system 180 and the scan optical system 108.

<Step S510, Step S511> (Adjustment of focus position)
In step S510, based on an instruction from the control unit 300, the stage 109 is driven and adjustment is performed so that a desired retinal layer is in focus. It is also possible to adjust the focus position by superimposing defocus on the wavefront correction device 104. Further, the coherence gate can be moved so that the S / N ratio of the signal of the desired retinal layer can be adjusted. At this time, adjustment is performed so that the folded image at the coherence gate does not overlap at a desired photographing position. Further, the user can finely adjust the coherence gate position with the slider 432.

  In step S511, it is determined whether further photographing in the depth direction is necessary. If necessary, the process returns to S510 to adjust the focus position again. If not necessary, the process proceeds to S512.

<Step S512> (Moving the shooting position (x, y))
It is determined whether or not it is necessary to move the shooting position (x, y) in order to perform shooting while dividing the region, or to perform shooting again when shooting fails, and return to S509 if necessary. Then, the fixation fixation guidance and the steering adjustment are performed. If unnecessary, the process proceeds to S513.

<Step S513> (judgment completion)
It is determined whether or not shooting has been completed. If completed, the process proceeds to S514. If shooting is to be continued, the process proceeds to S502.

<Step S514> (Image composition)
When a plurality of OCT images are acquired, areas with high contrast and high S / N ratio are combined and displayed on the display area 408.

  In the four OCT images acquired in FIG. 7B, regions 703-1 to 703-4 are cut out to create a combined image. Pasting is performed by aligning the overlapping areas of the images set in step S508. Further, when the overlap is small, for example, the low-resolution OCT image 701 may be used as a reference image to perform alignment with an image with a reduced resolution of the AO-OCT image to obtain a rough bonding position. The pasted image is trimmed so as to roughly match the shooting range designated by the mark 413 and displayed in the display area 408.

  Regarding the OCT image acquired in FIG. 7C, the regions 704-2 to 704-5 are pasted together using the region 704-1 as a reference image. By acquiring the reference image at a position approximately in the center of the photographing range, the overlapping area becomes large, and it is possible to improve the bonding accuracy.

  As described above, according to the present embodiment, the acquisition position of the high-resolution tomographic image can be specified with the low-resolution tomographic image, so that the blood vessel structure and the lesion can be extracted efficiently. Furthermore, it is possible to easily specify the position of a high-resolution tomographic image, thereby reducing the burden on the patient.

[Example 2]
In the above-described first embodiment, the procedure for capturing a high-resolution tomographic image has been described. In the present embodiment, as a tomographic image acquisition apparatus, a process in a case where the imaging position of a high-resolution tomographic image acquired by an ophthalmologic imaging apparatus is presented to a user will be described.

  First, a plurality of high-resolution tomographic images acquired as shown in the first embodiment are stored in the storage unit 600 together with the captured position information.

  Based on a user instruction, the control unit 300 displays a list of a plurality of high-resolution tomographic images read from the storage unit 600 on a display device. Then, the selected high-resolution tomographic image is displayed in the display area 408 of FIG. At the same time, the low-resolution tomographic image and the position information stored in the storage unit 600 in association with the selected high-resolution tomographic image are read out, and the low-resolution tomographic images are respectively displayed in the display areas 406 and 407 based on the position information. Display a tomographic image. Then, rectangular marks 413 indicating the corresponding positions of the high-resolution tomographic image are displayed on the low-resolution tomographic images displayed in the display areas 406 and 407. Furthermore, the corresponding positions of the low-resolution tomographic images displayed in the display areas 406 and 407 are displayed on the fundus image, which is a planar image of the fundus oculi generated from a plurality of low-resolution tomographic images displayed in the display area 405. Dashed lines 411-1 and 411-2 are displayed. The planar image of the fundus does not necessarily need to be a two-dimensional image, and is a three-dimensional image (for example, an image displayed in the display area 405 in FIG. 4) in which the fundus plane (surface) can be confirmed. Also good.

  As described above, according to the present embodiment, the acquisition position of a high-resolution tomographic image can be displayed in an easy-to-understand manner.

[Other Examples]
In the embodiment described above, the imaging data is obtained by spectral domain OCT using a broadband light source for the eye 118 to be examined. However, the present invention is not limited to this, and for example, wavelength sweep type OCT is used. May be.

  In the above-described embodiment, the case where the subject is an eye is described. However, the present invention can also be applied to a subject such as a skin or an organ other than the eye. In this case, the present invention has an aspect as a medical device such as an endoscope other than the ophthalmologic photographing apparatus. Therefore, it is preferable that the present invention is grasped as an image acquisition device exemplified by an ophthalmologic photographing apparatus, and the eye to be examined is grasped as one aspect of the subject.

  The present invention can also be achieved by configuring the apparatus as follows. That is, a recording medium (or storage medium) that records software program codes (computer programs) that implement the functions of the above-described embodiments may be supplied to the system or apparatus. In addition to the form of the recording medium, a computer-readable recording medium may be used. Then, the computer (or CPU or MPU) of the system or apparatus reads and executes the program code stored in the recording medium. In this case, the program code itself read from the recording medium realizes the functions of the above-described embodiment, and the recording medium on which the program code is recorded constitutes the present invention. The embodiment can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

Claims (12)

First designation means for designating a first position for acquiring a low-resolution tomographic image in the fundus image of the eye to be examined;
First acquisition means for acquiring a low-resolution tomographic image corresponding to the first position;
A second designating unit for designating a second position for acquiring a high-resolution tomographic image with the resolution tomographic image;
An ophthalmologic imaging apparatus comprising: a second acquisition unit that acquires a high-resolution tomographic image based on the first position and the second position.   The tomographic image acquisition apparatus according to claim 1, wherein the fundus image of the eye to be examined is an image generated by projecting a plurality of low-resolution tomographic images in the optical axis direction. Splitting means for splitting light from the light source into measurement light and reference light;
Control means for adjusting an optical path length difference between the measurement light and the reference light;
Focusing means for adjusting the focus position of the measurement light;
The focus means adjusts a focus position when acquiring the high-resolution tomographic image based on information on an optical path length difference when the low-resolution tomographic image is acquired. The tomographic image acquisition apparatus according to 2. A correction means for correcting the aberration of the return light caused by irradiating the eye to be examined with the measurement light;
The second position is designated as a rectangular region;
When the horizontal size of the designated rectangular area exceeds the size that can be corrected by the correcting means, the second acquiring means obtains a high-resolution tomographic image for each area obtained by dividing the rectangular area into a plurality of areas. The tomographic image acquisition apparatus according to claim 3, wherein:   The tomographic image acquisition apparatus according to claim 4, further comprising a pasting unit that creates a single tomographic image by pasting the acquired plurality of high-resolution tomographic images. Further comprising an alignment means for selecting and aligning a reference image from the acquired plurality of high-resolution tomographic images,
6. The tomographic image acquisition apparatus according to claim 5, wherein the pasting unit pastes the plurality of aligned high-resolution tomographic images.   The said 2nd acquisition means gives priority to the acquisition of the area | region of a vertical direction, when there exist two or more in the said vertical direction and the horizontal direction, respectively, The said 2nd acquisition means gives priority to acquisition of the area | region of the vertical direction. The tomographic image acquisition device according to item. A changer for changing a beam diameter of the measurement light;
The said 1st acquisition means and the said 2nd acquisition means differ in the beam diameter of the said measurement light, The beam diameter of the said 2nd acquisition means is large, The any one of Claim 3 thru | or 7 characterized by the above-mentioned. The tomographic image acquisition apparatus described in 1. Display means having a first display area for displaying a high-resolution tomographic image, a second display area for displaying a low-resolution tomographic image, and a third display area for displaying a planar image;
Corresponding positions of the high-resolution tomographic image displayed in the first display area are displayed on the low-resolution tomographic image displayed in the second display area and the planar image displayed in the third display area. A tomographic image acquisition apparatus having a control means for displaying each.   The tomographic image acquisition apparatus according to claim 9, wherein the planar image is a planar image of the fundus oculi generated by projecting a plurality of low-resolution tomographic images in the optical axis direction. A first designation step for designating a first position for acquiring a low-resolution tomographic image in the fundus image of the eye to be examined;
A first acquisition step of acquiring a low-resolution tomographic image corresponding to the first position;
A second designating step of designating a second position for acquiring a high-resolution tomographic image in the tomographic image of the resolution;
A tomographic image acquisition method comprising: a second acquisition step of acquiring a high-resolution tomographic image based on the first position and the second position. A display step of displaying a high-resolution tomographic image in the first display area of the display means, displaying a low-resolution tomographic image in the second display area, and displaying a planar image in the third display area;
Corresponding positions of the high-resolution tomographic image displayed in the first display area are displayed on the low-resolution tomographic image displayed in the second display area and the planar image displayed in the third display area. A tomographic image acquisition method comprising: a control step of displaying each.

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