Ophthalmic device and image processing method

Abstract

To provide an ophthalmologic apparatus and image processing method which measure the state of a blood vessel of an ocular fundus.SOLUTION: A vascular elasticity rate measurement device comprises: an ultrasonic irradiation unit which applies an acoustic radiation force to a subject eye; a tomographic image acquisition unit which acquires a tomographic image of the ocular fundus of the subject eye; and a control unit which controls the ultrasonic irradiation unit and the tomographic image acquisition unit so as to acquire a first tomographic image of the ocular fundus in such a state that the ultrasonic wave is irradiated to the subject eye with the first output from the ultrasonic irradiation unit and acquire a second tomographic image of the ocular fundus in a state that the ultrasonic wave is irradiated to the subject eye with the second output different from the first output from the ultrasonic irradiation unit, and calculates the vascular elasticity rate of the ocular fundus on the basis of the first tomographic image and second tomographic image.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an ophthalmic apparatus and an image processing method.

Background Art

[0002] Patent Document 1 discloses an invention for predicting the risk of glaucoma onset in an eye to be examined. In order to predict diseases such as glaucoma in the eye to be examined, it is required to measure the state of blood vessels in the fundus of the eye.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] An ophthalmic apparatus according to a first aspect of the technology of the present disclosure includes an ultrasonic irradiation unit that applies ultrasonic waves to an eye to be examined, a tomographic image acquisition unit that acquires a tomographic image of the eye to be examined, and a first tomographic image of the eye to be examined is acquired in a state where the first ultrasonic wave is irradiated to the eye to be examined with a first output from the ultrasonic irradiation unit, and a second tomographic image of the eye to be examined is acquired in a state where the second ultrasonic wave is irradiated to the eye to be examined with a second output different from the first output from the ultrasonic irradiation unit. The ultrasonic irradiation unit and the tomographic image acquisition unit are controlled, and a control unit that calculates an elastic modulus of blood vessels in the eye to be examined based on the first tomographic image and the second tomographic image.

[0005] An image processing method according to a second aspect of the technology of the present disclosure includes acquiring a first tomographic image of an eye to be examined in a state where a first ultrasonic wave is irradiated to the eye to be examined with a first output from an ultrasonic irradiation unit, acquiring a second tomographic image of the eye to be examined in a state where a second ultrasonic wave is irradiated to the fundus of the eye with a second output different from the first output, and calculating an elastic modulus of blood vessels in the eye to be examined based on the first tomographic image and the second tomographic image.

Brief Description of the Drawings

[0006]

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Mode for Carrying Out the Invention

[0007] [First Embodiment] Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an ophthalmic system 100. As shown in FIG. 1, the ophthalmic system 100 includes an ophthalmic device 110, a server device (hereinafter referred to as “server”) 140, and a display device (hereinafter referred to as “viewer”) 150. The ophthalmic device 110 acquires fundus images. The server 140 stores a plurality of fundus images obtained by photographing the fundus of a plurality of patients by the ophthalmic device 110 in correspondence with the patient IDs. The viewer 150 displays the fundus images and analysis results acquired by the server 140.

[0008] The ophthalmic device 110 is a device for photographing an eye to be examined, photographs the posterior segment and anterior segment of the eye to be examined, and acquires a fundus image and an anterior segment image. And it is provided with an optical coherence tomography (OCT) for acquiring a tomographic image of the eye to be examined. It may be a device that combines other modalities such as a fundus camera and a scanning laser ophthalmoscope (SLO) in addition to OCT.

[0009] The server 140 stores the images of the eyes to be examined photographed by the ophthalmic device 110 in correspondence with the patient IDs. The viewer 150 displays the data (images of the eyes to be examined, analysis results for assisting diagnosis, etc.) acquired by the server 140.

[0010] The ophthalmic device 110, the server 140, and the viewer 150 are interconnected via the network 130. The viewer 150 is a client in a client-server system, and multiple viewers can be connected via the network. Also, multiple servers 140 may be connected via the network to ensure system redundancy. Alternatively, if the ophthalmic device 110 has an image processing function and an image viewing function of the viewer 150, the ophthalmic device 110 can be in a stand-alone state, enabling acquisition, processing, and viewing of fundus images. Further, if the server 140 has an image viewing function of the viewer 150, acquisition, processing, and viewing of fundus images are possible with the configuration of the ophthalmic device 110 and the server 140.

[0011] Note that other ophthalmic devices (examination devices such as perimetry and tonometry) and a diagnostic support device that performs image analysis using AI (Artificial Intelligence) may be connected to the ophthalmic device 110, the server 140, and the viewer 150 via the network 130.

[0012] Next, with reference to FIG. 2, the configuration of the ophthalmic device 110 will be described. When the ophthalmic device 110 is installed on a horizontal plane, the horizontal direction is defined as the "X direction", the vertical direction with respect to the horizontal plane is defined as the "Y direction", and the direction connecting the center of the pupil 27 of the anterior eye part of the eye to be examined 12 and the center O of the eyeball is defined as the "Z direction". Therefore, the X direction, the Y direction, and the Z direction are perpendicular to each other.

[0013] The ophthalmic device 110 includes a photographing device 14 and a control device 116. The photographing device 14 has a configuration including an SLO unit 18 and an OCT unit 200. The two-dimensional fundus image acquired by the SLO unit 18 is referred to as an SLO image. Also, a tomographic image or an en-face image of the retina created based on the OCT data acquired by the OCT unit 200 is referred to as an OCT image. The OCT image corresponds to the "tomographic image" of the technology of the present disclosure.

[0014] The control device 116 includes a computer having a CPU (Central Processing Unit), a RAM (Random Access Memory) 16B, a ROM (Read-Only Memory) 16C, and an input / output (I / O) port 16D.

[0015] The control device 116 includes an input / display device 16E connected to the CPU 16A via the I / O port 16D. The input / display device 16E has a graphic user interface for displaying an image of the eye to be examined 12 and receiving various instructions from the user. Examples of the graphic user interface include a touch panel display.

[0016] Further, the control device 116 includes an image processing device 17 connected to the I / O port 16D. The image processing device 17 generates an image of the eye to be examined 12 based on the data obtained by the imaging device 14 and executes various image processes in cooperation with the CPU 16A. Note that the control device 116 is connected to the network 130 via the communication interface 16F.

[0017] As described above, in FIG. 2, the control device 116 of the ophthalmic device 110 includes the input / display device 16E, but the technology of the present disclosure is not limited thereto. For example, the control device 116 of the ophthalmic device 110 may not include the input / display device 16E and may include a separate input / display device physically independent of the ophthalmic device 110.

[0018] The imaging device 14 operates under the control of the CPU 16A of the control device 116. The imaging device 14 includes an SLO unit 18, an imaging optical system 19, and an OCT unit 200. The imaging optical system 19 includes an optical scanner 22 and a wide-angle optical system 30.

[0019] The optical scanner 22 two-dimensionally scans the light emitted from the SLO unit 18 in the X direction and the Y direction. The optical scanner 22 may be an optical element capable of deflecting a light beam. For example, a polygon mirror, a galvanometer mirror, or the like can be used. Also, a combination thereof may be used.

[0020] The wide-angle optical system 30 guides the light from the SLO unit 18 to the eye to be examined 12. The wide-angle optical system 30 may be a reflective optical system using a concave mirror such as an elliptical mirror, a refractive optical system using a wide-angle lens, or a catadioptric optical system combining a concave mirror and a lens. By using a wide-angle optical system using an elliptical mirror or a wide-angle lens, it is possible to photograph the retina not only at the center of the fundus but also at the peripheral part of the fundus.

[0021] When using a system including an elliptical mirror, a configuration using the system with an elliptical mirror described in International Publication WO2016 / 103484 or International Publication WO2016 / 103489 may be used. The disclosures of International Publication WO2016 / 103484 and International Publication WO2016 / 103489 are each incorporated herein by reference in their entirety.

[0022] The wide-angle optical system 30 enables observation in a wide field of view (FOV) 12A in the fundus. The FOV 12A indicates the range that can be photographed by the imaging device 14. The FOV 12A can be expressed as a viewing angle. The viewing angle can be defined by an internal irradiation angle and an external irradiation angle in the present embodiment. The external irradiation angle is the irradiation angle of the light beam irradiated from the ophthalmic device 110 to the eye to be examined 12, defined with respect to the pupil 27. The internal irradiation angle is the irradiation angle of the light beam irradiated to the fundus, defined with respect to the center O of the eyeball. The external irradiation angle and the internal irradiation angle are in a corresponding relationship. For example, when the external irradiation angle is 120 degrees, the internal irradiation angle corresponds to about 160 degrees. In the present embodiment, the internal irradiation angle is set to 200 degrees.

[0023] Here, an SLO fundus image obtained by imaging with a shooting angle of 160 degrees or more at the internal irradiation angle is referred to as a UWF-SLO fundus image. Note that UWF is an abbreviation for UltraWide Field (ultra-wide angle). With a wide-angle optical system 30 having an ultra-wide angle as the visual field angle (FOV) of the fundus, it is possible to image a region extending from the posterior pole to beyond the equator of the fundus of the eye to be examined 12, and structures existing in the peripheral part of the fundus such as retinal blood vessels can be imaged.

[0024] The SLO system is realized by a control device 116, an SLO unit 18, and an imaging optical system 19 shown in FIG. 2. Since the SLO system includes a wide-angle optical system 30, it enables fundus imaging with a wide FOV 12A.

[0025] The SLO unit 18 includes a light source 40 for B (blue light), a light source 42 for G light (green light), a light source 44 for R light (red light), and a light source 46 for IR light (infrared light (for example, near-infrared light)), and optical systems 48, 50, 52, 54, 56 that reflect or transmit the light from the light sources 40, 42, 44, 46 and guide it to one optical path. The optical systems 48, 56 are mirrors, and the optical systems 50, 52, 54 are beam splitters. The B light is reflected by the optical system 48, transmitted through the optical system 50, and reflected by the optical system 54. The G light is reflected by the optical systems 50, 54. The R light is transmitted through the optical systems 52, 54. The IR light is reflected by the optical systems 52, 56 and is respectively guided to one optical path.

[0026] The SLO unit 18 is configured to be able to switch combinations of light sources that emit laser light or cause emission of laser light with different wavelengths, such as a mode that emits R light and G light and a mode that emits infrared light. In the example shown in FIG. 2, it includes four light sources: a light source 40 for B light, a light source 42 for G light, a light source 44 for R light, and a light source 46 for IR light. However, the technology of the present disclosure is not limited to this. For example, the SLO unit 18 may further include a light source for white light and emit light in various modes such as a mode that emits G light, R light, and B light or a mode that emits only white light.

[0027] The light incident from the SLO unit 18 on the imaging optical system 19 is scanned in the X direction and the Y direction by the optical scanner 22. The scanned light is irradiated onto the fundus via the wide-angle optical system 30 and the pupil 27. The reflected light reflected by the fundus is incident on the SLO unit 18 via the wide-angle optical system 30 and the optical scanner 22.

[0028] The SLO unit 18 includes a beam splitter 64 that reflects B light and transmits light other than B light among the light from the posterior segment (fundus) of the eye to be examined 12, and a beam splitter 58 that reflects G light and transmits light other than G light among the light transmitted through the beam splitter 64. The SLO unit 18 includes a beam splitter 60 that reflects R light and transmits light other than R light among the light transmitted through the beam splitter 58. The SLO unit 18 includes a beam splitter 62 that reflects IR light among the light transmitted through the beam splitter 60. The SLO unit 18 includes a B light detection element 70 that detects the B light reflected by the beam splitter 64, a G light detection element 72 that detects the G light reflected by the beam splitter 58, an R light detection element 74 that detects the R light reflected by the beam splitter 60, and an IR light detection element 76 that detects the IR light reflected by the beam splitter 62.

[0029] The light (reflected light reflected by the fundus) incident on the SLO unit 18 via the wide-angle optical system 30 and the optical scanner 22 is reflected by the beam splitter 64 and received by the B light detection element 70 in the case of B light, and is reflected by the beam splitter 58 and received by the G light detection element 72 in the case of G light. The above-incident light is transmitted through the beam splitter 58 and reflected by the beam splitter 60 and received by the R light detection element 74 in the case of R light. The above-incident light is transmitted through the beam splitters 58 and 60 and reflected by the beam splitter 62 and received by the IR light detection element 76 in the case of IR light. The image processing device 17 operating under the control of the CPU 16A generates a UWF-SLO image using the signals detected by the B light detection element 70, the G light detection element 72, the R light detection element 74, and the IR light detection element 76.

[0030] Further, the control device 116 controls the light sources 40, 42, and 44 to emit light simultaneously. By photographing the fundus of the eye 12 simultaneously with B light, G light, and R light, G-color fundus images, R-color fundus images, and B-color fundus images in which each position corresponds to each other are obtained. An RGB color fundus image is obtained from the G-color fundus image, the R-color fundus image, and the B-color fundus image. The control device 116 controls the light sources 42 and 44 to emit light simultaneously, and by photographing the fundus of the eye 12 simultaneously with G light and R light, G-color fundus images and R-color fundus images in which each position corresponds to each other are obtained. An RG color fundus image is obtained from the G-color fundus image and the R-color fundus image.

[0031] The OCT system is realized by the control device 116 and the OCT unit 200 shown in FIG. 2. The OCT unit 200 is a device capable of full-field OCT that collectively acquires OCT data of the fundus by collectively irradiating the fundus of the eye 12 with measurement light. The OCT unit 200 can acquire OCT data of structures existing in the peripheral part of the fundus such as retinal blood vessels, and can obtain a tomographic image of the retinal blood vessels and a 3D structure of the retinal blood vessels by performing image processing on the OCT data.

[0032] With reference to FIG. 2, the configuration of the optical system of the OCT unit 200 will be described. The OCT unit 200 shown in FIG. 2 includes a wavelength-sweeping type light source 160, a polarizing plate 162 that converts the polarization characteristics of the light beam into linearly polarized light, lenses 164 and 166 that make the light beam a parallel light beam and expand its beam diameter, a cube-type beam splitter 168 that splits the light beam into a measurement light 192 and a reference light 190 and interferes them to generate an interference light 194, a wave plate 170 that imparts polarization to the reference light 190, and a reflecting mirror 172 that totally reflects the reference light 190 by a reflecting surface orthogonal to the traveling direction of the reference light 190.

[0033] The XYZ coordinate system shown in FIG. 2 defines the propagation direction of the light beam output from the light source 160 as the Z direction, and the vibration plane of the light beam orthogonal thereto as the X-Y plane. The X direction and the Y direction are defined so as to coincide with the vibration plane of the electric field (electric field) component and the vibration plane of the magnetic field (magnetic field) component of the light beam. The Z direction is defined as the propagation direction of the measurement light 192 toward the eye to be examined 12, and is also defined as the measurement depth direction of the eye to be examined 12.

[0034] The polarizing plate 162 is a polarizing element composed of a linear polarizer for adjusting the polarization direction of the light beam from the light source 160. The polarizing plate 162 in the present embodiment is configured to transmit the vibration components in the angular directions making 45° with respect to the X axis and the Y axis of the XYZ coordinate system, respectively. Thereby, the light beam transmitted through the polarizing plate 162 has linearly polarized light at an angle of 45°. Therefore, the polarization components of the light beam in the X-axis direction and the Y-axis direction have equal amplitudes, respectively. In other words, the P-polarization component and the S-polarization component of the light beam have equal amplitudes, respectively.

[0035] The cube beam splitter 168 acts to split the linearly polarized light beam made into a parallel light beam into the measurement light 192 toward the eye to be examined 12 and the reference light 190 toward the mirror 172. The cube beam splitter 168 reflects a part (half) of the light beam to form the reference light 190 and transmits the remainder to form the measurement light 192. The formed measurement light is irradiated onto the eye to be examined 12 through the objective lens 176.

[0036] The cube beam splitter 168 generates the interference light 194 by interfering the measurement light 192 and the reference light 190 by reflecting a part of the measurement light 192 that has passed through the eye to be examined 12 and transmitting a part of the reference light 190 that has passed through the mirror 172.

[0037] The wavelength plate 170 is a polarization conversion element that converts the polarization characteristics of the reference light 190 linearly polarized by the polarizing plate 162. As the wavelength plate 170 in the present embodiment, a quarter-wave plate is used. Thereby, when the reference light 190 passes through the wavelength plate 170, a phase difference of π / 4 is given between its P polarization component and S polarization component. Since the reference light 190 is given the phase difference when it travels from the cube beam splitter 168 toward the mirror 172 and when it is reflected by the mirror 172 and re-enters the cube beam splitter 168, a phase difference of π / 2 is ultimately given. Therefore, since it acts in the same way as a quarter-wave plate with respect to the reference light 190 having linearly polarized light at 45°, the reference light 190 re-entering the cube beam splitter 168 is converted into circularly polarized light.

[0038] The interference light 194 is generated by the interference of the measurement light 192 and the reference light 190. The OCT unit 200 includes an imaging lens group 178 for imaging the interference light 194 generated by the cube beam splitter 168, and a CCD (Charge Coupled Device) 182 which is a full-field sensor provided on the optical path of the interference light 194.

[0039] The CCD 182 is a two-dimensional optical sensor array for detecting interference light. The image processor 17 of the control device 116 executes image processing based on the detection signals output from the CCD 182 respectively, and performs a process of forming a tomographic image of the eye to be examined 12. The OCT unit 200 is capable of Full field OCT that acquires an X-Y tomographic image of an arbitrary depth region of the eye to be examined 12 in a single shot, that is, over the entire field of view.

[0040] Also, the ophthalmic device 110 in the present embodiment includes an ultrasonic probe 120 that irradiates ultrasonic waves to the eye to be examined. The ultrasonic probe 120 applies pressure by acoustic radiation force to the eye to be examined 12 under the control of the control device 116. The eye to be examined is compressed by the ultrasonic waves, and the blood vessels of the eye to be examined are compressed.

[0041] By irradiating the fundus of the eye with ultrasonic waves generated from the ultrasonic probe 120, the retinal blood vessels are compressed. The ultrasonic probe may be configured to be adjusted to converge on the retina or to generate focused ultrasonic waves so that the ultrasonic waves are irradiated onto the retinal blood vessels for which the elastic modulus is to be measured.

[0042] FIG. 4 is a flowchart showing the elastic modulus measurement process of the retinal blood vessels in the present embodiment. A case where the process shown in FIG. 4 is executed by the control device 116 of the ophthalmic device 110 will be described. Various functions realized by the CPU 16A of the control device 116 executing a program will be described. As shown in FIG. 3, the program includes an OCT data acquisition function, an image processing function, and a processing function. By the CPU 16A executing a program having such functions, the CPU 16A functions as an OCT data acquisition unit 204, an image processing unit 206, and a processing unit 208. Note that the image processing function includes being achieved by the cooperation of the CPU 16A and the image processing device 17. Further, the program is a computer program product for image processing, and the computer program product includes a computer-readable storage medium that is not a temporary signal itself, and the program is stored in the computer-readable storage medium. The program causes the computer to execute a step of acquiring a first tomographic image of the subject eye with the ultrasonic irradiation unit turned off, a step of acquiring a second tomographic image of the subject eye with the ultrasonic waves irradiated from the ultrasonic irradiation unit to the subject eye, and a step of calculating the elastic modulus of the blood vessels of the subject eye based on the first tomographic image and the second tomographic image. In the present embodiment, by executing such a program, the process shown in FIG. 4 is realized.

[0043] In step 500, the OCT data acquisition unit 204 controls the OCT unit 200 to perform alignment and focus adjustment with the subject eye 12, etc., so that the OCT data of the fundus of the subject eye 12 can be acquired.

[0044] In step 502, the OCT data acquisition unit 204 sets the OCT scan position. In the present embodiment, full-field OCT is performed to collectively acquire OCT data of a predetermined region of the fundus. The predetermined region is defined by the size of the imaging area of the CCD 182, which is a two-dimensional optical sensor array. The OCT scan position may be set such that the position of the predetermined region is centered on the optic nerve head. Alternatively, by changing the presentation position of a fixation target (not shown) and changing the orientation of the test eye 12 with respect to the optical axis, the position of the predetermined region may be set in the peripheral part of the fundus.

[0045] In step 504, the OCT data acquisition unit 204 acquires the first OCT data at the set OCT scan position without operating the ultrasonic probe 120 (set to OFF). The first OCT data is OCT data of a predetermined region in a state without ultrasonic irradiation. Then, the processing unit 208 stores and holds the acquired first OCT data in the RAM 16B.

[0046] In step 506, the OCT data acquisition unit 204 operates the ultrasonic probe 120 (set to ON) to irradiate the test eye 12 with ultrasonic waves. FIG. 5 is a schematic diagram showing ultrasonic irradiation of the test eye 12. The ultrasonic probe 120 irradiates the fundus of the test eye 12 with focused ultrasonic waves having a frequency and output sufficient to constrict the retinal blood vessels. The intensity of the ultrasonic waves during irradiation is constant, and since the irradiation intensity must be non-invasive, it is desirable to set the upper limit to about 500 Pa.

[0047] FIG. 6 is an explanatory diagram showing the effect of ultrasonic irradiation on the fundus of the test eye 12. As shown in FIG. 6, due to the ultrasonic irradiation of the fundus, the vessel wall 302 of the retinal blood vessels is compressed, and the retinal blood vessels are compressed in the Z-axis direction. The elastic modulus of the retinal blood vessels can be measured from the first OCT data and the second OCT data.

[0048] FIG. 7 is an explanatory diagram of strain imaging showing differences in Young's modulus, blood vessel diameter displacement, and blood vessel strain due to differences in hardening when a soft object and a hard object (blood vessel) coexist. The higher the Young's modulus, the more the hardening of the blood vessel wall has progressed. Also, the Young's modulus increases as the displacement or strain of the object with respect to the action of stress increases. In the present embodiment, based on the OCT data when the fundus of the eye 12 is irradiated with ultrasonic waves and the OCT data when not irradiated with ultrasonic waves, the Young's modulus indicating the elastic modulus of the retinal blood vessels is calculated. That is, in the OCT data when irradiated with ultrasonic waves, the harder the blood vessel wall (the higher the Young's modulus), the smaller the strain of the blood vessel wall, and the softer the blood vessel wall (the smaller the Young's modulus), the larger the strain of the blood vessel wall. Therefore, by measuring the magnitude of the strain from the OCT data when the fundus of the eye 12 is irradiated with ultrasonic waves and the OCT data when not irradiated with ultrasonic waves, the Young's modulus of the blood vessel wall at the measurement time point can be calculated.

[0049] In step 508, the OCT data acquisition unit 204 acquires the second OCT data at the set OCT scan position while the eye 12 to be examined is irradiated with ultrasonic waves. The scan position of the second OCT data is the same as the scan position of the first OCT data. The second OCT data is OCT data of a predetermined region in the ultrasonic wave irradiation state. Then, the processing unit 208 stores and holds the acquired second OCT data in the RAM 16B. Then, in step 510, the OCT data acquisition unit 204 stops the operation of the ultrasonic probe 120 (sets it to OFF), and the irradiation of ultrasonic waves is stopped.

[0050] In step 512, the image processing unit 206 calculates the elastic modulus of the blood vessels from the first OCT data and the second OCT data.

[0051] FIG. 8 is a flowchart showing the elastic modulus calculation process of the blood vessels in step 512 of FIG. 4. In step 900, the image processing unit 206 acquires the first OCT data and the second OCT data from the RAM 16B. The process shown in FIG. 8 may be performed by the CPU provided in the server 140.

[0052] In step 902, the image processing unit 206 identifies a first blood vessel region that is a target region for calculating the elastic modulus of a blood vessel. The first blood vessel region may be identified by extracting a region where a blood vessel exists using the first OCT data, or may be identified by extracting a region where a blood vessel exists using the SLO data in combination. Alternatively, the region may be identified by angiography (angioplasty) using a contrast agent. For example, in the fundus of the eye, the crossing portion of the retinal blood vessels is a site where vitreous hemorrhage or retinal detachment is likely to occur, so a region including the crossing portion of the blood vessels may be preferentially identified as the first blood vessel region. Also, in the present embodiment, since full-field OCT capable of collectively acquiring OCT data of the fundus by collectively irradiating the measurement light to the fundus of the test eye 12 is possible, the entire fundus may be used as the first blood vessel region.

[0053] FIGS. 9A, 9B, 9C, and 9D are schematic views showing examples of arteriovenous crossing phenomena. FIG. 9A shows a state in which the vein 300V at the crossing portion with the artery 300A is curved in an arc shape because the artery 300A extending to the obliterated side due to arteriosclerosis pulls the vein 300V through the blood vessel wall.

[0054] FIG. 9B shows a state in which arteriosclerosis has progressed and the blood vessel wall of the artery 300A has become thick, hiding the vein 300V at the crossing portion (because the measurement light is blocked by the blood vessel wall of the artery 300A and does not reach the vein 300V), and the blood flow of the vein 300V appears to have stopped.

[0055] Also, as shown in FIG. 9C, there is a state in which the blood vessel wall of the artery 300A with advanced arteriosclerosis hides the blood flow of the vein 300V, and the tip of the vein 300V at the crossing portion appears to be thin.

[0056] FIG. 9D shows a state in which the blood vessel wall of the artery 300A thickened by arteriosclerosis is obstructing the blood flow of the vein 300V, and the vein 300V is dilated on the peripheral side and in a congested state.

[0057] In this embodiment, the region in the state illustrated in FIGS. 9A, 9B, 9C, and 9D may be preferentially specified as the first blood vessel region.

[0058] In step 904, the thickness of the blood vessels in the first blood vessel region is measured based on the first OCT data. The thickness of the blood vessels to be measured is the diameter in the A-scan direction (the diameter in the depth direction of the retina).

[0059] In step 906, the second blood vessel region in the second OCT data is specified. The second blood vessel region is the region corresponding to the first blood vessel region of the first OCT data in the second OCT data.

[0060] In step 908, the thickness of the blood vessels in the second blood vessel region is measured based on the second OCT data. The thickness of the blood vessels to be measured is the diameter in the A-scan direction (the diameter in the depth direction of the retina), and when the cross-section of the blood vessels compressed by the focused ultrasound is an ellipse, it corresponds to the minor axis of the ellipse.

[0061] In step 910, the elastic modulus of the blood vessels is calculated. The elastic modulus of the blood vessels is calculated based on the thickness of the blood vessels in the first blood vessel region and the thickness of the blood vessels in the second blood vessel region. In this embodiment, when the difference between the thickness of the blood vessels in the first blood vessel region and the thickness of the blood vessels in the second blood vessel region is defined as the strain ε, and the pressure (stress) exerted by the ultrasonic probe 120 on the fundus of the eye 12 to be examined is defined as σ, the Young's modulus E indicating the elastic modulus of the blood vessels is calculated by the following formula (1).

[0062] E = σ / ε …(1)

[0063] In step 912, the data of the elastic modulus of the blood vessels is stored in the storage device of the server 140, and the process shown in FIG. 8 is terminated. Then, the process returns to step 514 in FIG. 4. The data of the elastic modulus of the blood vessels may be data combining the position of the pixels of the blood vessels and the elastic modulus at that position. Further, the data may include the luminance of the pixels, the blood vessel diameter, and the like.

[0064] In step 514, the image processing unit 206 generates a display screen 500 shown in FIG. 10 to be displayed on the input / display device 16E. Next, in step 516, the processing unit 208 stores data for displaying the display screen 500 in the storage device of the server 140. Then, in step 518, the processing unit 208 outputs an image signal of the display screen 500 to the input / display device 16E based on a display request from the user. The display screen 500 is displayed on the input / display device 16E based on the image signal.

[0065] Hereinafter, the details of the display screen 500 will be described. The display screen 500 includes an information display area 502, an image display area 504, and an elastic modulus information display area 506. The information display area 502 includes a patient ID display area 512, a patient name display area 514, an age display area 516, a visual acuity display area 518, a right eye / left eye display area 520, and an axial length display area 522. In the information display area 502, based on the information received from the server 140, the respective information is displayed in each display area from the patient ID display area 512 to the axial length display area 522.

[0066] The image display area 504 is an area for displaying a fundus image or the like. In FIG. 10, a fundus image 530 obtained by full field OCT and tomographic images 532 and 534 of blood vessels at the position indicated by the arrow 536 are respectively displayed. The blood vessels displayed in the fundus image 530 are subjected to a change in display form such as color-coding according to the elastic modulus. Generally, the elastic modulus of a healthy retina is about 10 kPa. The elastic modulus of retinal blood vessels has a certain width and is about 10 kPa to 30 kPa. Further, the fundus image 530 may be an SLO image instead of an en-face image generated from OCT data. In this case, registration between the SLO image and the en-face image may be performed, and image processing such as color-coding the blood vessel portion of the SLO image using elastic modulus data may be performed.

[0067] The tomographic image 532 is a tomographic image of a blood vessel before ultrasonic irradiation, and the tomographic image 534 is a tomographic image during ultrasonic irradiation.

[0068] Arrow 536 moves in conjunction with a pointing device such as a touch panel or a mouse provided in the input / display device 16E, so the user can check the tomographic images 532 and 534 of blood vessels at any position indicated by the pointing device.

[0069] In the elastic modulus information display area 506, information such as the elastic modulus of blood vessels at any position indicated by the pointing device, the blood vessel diameter with ultrasonic irradiation OFF, and the blood vessel diameter with ultrasonic irradiation ON is displayed.

[0070] As described above, in the present embodiment, focused ultrasound is irradiated onto the retina of the eye to be examined 12, and the elastic modulus of blood vessels can be calculated based on the displacement amount of the blood vessel diameter before and after ultrasonic irradiation measured by OCT. In addition, it is possible to measure the elastic modulus of blood vessels not only in the fundus but also in the anterior segment of the eye (such as near the ciliary body) in the same manner as that of the blood vessels in the fundus.

[0071] Measurement of the elasticity of retinal blood vessels is required for early detection of intraocular diseases such as retinal vein occlusion, vitreous hemorrhage, and retinal detachment. In particular, at the optic nerve head, near the macula, or at the arteriovenous crossing, it is required to detect the risk of lesions at an early stage based on the elastic modulus of retinal blood vessels.

[0072] Measurement of the elastic modulus of blood vessels is generally an invasive measurement in which a probe penetrates into the eye to be examined 12, but there is a problem that the burden on the patient is large. In addition, strain imaging, which is a kind of elastic measurement method, is easily affected by the movement of the living body, and high speed is required during measurement.

[0073] In this embodiment, since full-field OCT is used to collectively acquire OCT data of a predetermined region of the fundus, the measurement of the elastic modulus can be performed by calculating the elastic moduli of a plurality of blood vessels existing in the predetermined region. In the acquisition of OCT data obtained by two-dimensional scanning with a laser beam using a point sensor and a scanner, the state of the blood vessels may change during the period of performing the two-dimensional scanning due to the influence of pulsation, beating, fixation tremor, etc. In full-field OCT, the first OCT data of the predetermined region is imaged at the same time t1, and within the first OCT data, it is not photographed at different times depending on the location (the same applies to the second OCT data, which is photographed at the same time t2). Therefore, full-field OCT can perform more accurate elastic modulus measurement than two-dimensional scanning.

[0074] Also, the elastic modulus of a specific blood vessel may be calculated from among the plurality of blood vessels in the predetermined region, or further, the elastic modulus of a blood vessel at a specific position (for example, the blood vessel position designated by the user) may be calculated.

[0075] In this embodiment, non-invasive strain imaging is performed by irradiating the fundus of the eye to be examined 12 with focused ultrasound from the outside, and full-field OCT technology is applied to enable high-speed imaging, reducing the measurement error due to the movement of the living body, which is a weakness of strain imaging.

[0076] In this embodiment, ultrasound is not irradiated to the eye to be examined 12 when acquiring the first OCT data, and ultrasound is irradiated to the eye to be examined 12 when acquiring the second OCT data, but it is not limited to this. For example, ultrasound may be irradiated to the eye to be examined at the first output when acquiring the first OCT data, and ultrasound may be irradiated to the eye to be examined 12 at a second output different from the first output when acquiring the second OCT data. In such a case, in the above formula (1), the pressure (stress) σ at which the ultrasound probe 120 acts on the fundus of the eye to be examined 12 becomes a value corresponding to the difference between the first output and the second output. Also, with such a configuration, when ultrasound is not irradiated to the eye to be examined 12 when acquiring the first OCT data, the first output is set to 0.

[0077] In this embodiment, the processes shown in FIGS. 4 and 8 are performed by the ophthalmic apparatus 110. However, after the first OCT data and the second OCT data are acquired by the ophthalmic apparatus 110, they may be performed by the server 140. When performed by the server 140, steps 512 to 518 of the flowchart in FIG. 4 are executed by the CPU of the server 140, and a display screen 500 visualizing the elastic modulus of the retina is generated. The image signal of the generated display screen 500 is transmitted to the viewer 150 or the like via the network 130. Therefore, the user of the viewer 150 can view the display screen 500, and information for assisting in the diagnosis of the eye to be examined can be displayed.

[0078] Visualization of the elastic modulus of the retina is realized by the CPU of the server 140 executing an image processing program. By the CPU of the server 140 executing an image processing program corresponding to steps 512 to 518 of the flowchart in FIG. 4, the CPU of the server 140 functions as a display control unit, an image processing unit, and a processing unit, similar to the CPU 16A of the ophthalmic apparatus 110.

[0079] [Second Embodiment] Subsequently, a second embodiment of the present invention will be described in detail with reference to FIG. 11. This embodiment uses an OCT unit of a type that scans the eye to be examined by point scanning, and is different from the first embodiment in that the imaging optical system 119 includes an OCT scanner 24 for point scanning. However, since other configurations are the same as those in the first embodiment, the same reference numerals are given to the same configurations and detailed descriptions thereof are omitted. Point scanning is a scanning method in which a laser beam is irradiated onto a single point of the eye to be examined, and the reflected light from the eye to be examined is received by a point sensor. By scanning the laser beam, a predetermined region of the eye to be examined is photographed.

[0080] FIG. 11 is a block diagram showing the configuration of an ophthalmic apparatus 210 according to this embodiment. As shown in FIG. 11, the ophthalmic apparatus 210 includes an imaging device 14 and a control device 16. The imaging device 14 includes an SLO unit 18 and an OCT unit 20, and acquires a fundus image of the fundus of the eye 12 to be examined.

[0081] Similar to the first embodiment, the control device 16 includes a computer having a CPU 16A, a RAM 16B, a ROM 16C, and an I / O port 16D, and includes an input / display device 16E and an image processing device 17 connected to the CPU 16A via the I / O port 16D. Since the SLO unit 18 is the same as that in the first embodiment, a detailed description thereof will be omitted.

[0082] The OCT unit 20 is an OCT unit capable of point scanning. OCT imaging by point scanning is realized by the control device 16, the OCT unit 20, and the imaging optical system 119 shown in FIG. 11. Since the ophthalmic device 210 includes the wide-angle optical system 30, similar to the imaging of the SLO fundus image described above, OCT imaging of the peripheral fundus can be performed. That is, with the wide-angle optical system 30 having an ultra-wide-angle field of view (FOV) of the fundus, OCT imaging of a region exceeding the equator from the posterior pole of the fundus of the eye to be examined 12 can be performed. OCT data of structures existing in the peripheral fundus such as retinal blood vessels can be acquired, and a tomographic image of the retinal blood vessels and a 3D structure of the retinal blood vessels can be obtained by image processing of the OCT data.

[0083] The OCT unit 20 includes a light source 20A, a point sensor (detection element) 20B, a first optical coupler 20C, a reference optical system 20D, a collimating lens 20E, and a second optical coupler 20F.

[0084] The light emitted from the light source 20A is branched by the first optical coupler 20C. One of the branched lights is used as measurement light, collimated by the collimating lens 20E, and then two-dimensionally scanned in the X direction and the Y direction by the OCT scanner 24 and incident on the imaging optical system 19. The measurement light is irradiated onto the fundus via the wide-angle optical system 30 and the pupil 27. The measurement light reflected by the fundus is incident on the OCT unit 20 via the wide-angle optical system 30 and enters the second optical coupler 20F via the collimating lens 20E and the first optical coupler 20C. The OCT scanner 24 may be an optical element capable of deflecting a light beam. For example, a polygon mirror, a galvanometer mirror, or the like can be used. Also, a combination thereof may be used.

[0085] The other light emitted from the light source 20A and branched by the first optical coupler 20C is incident on the reference optical system 20D as reference light, and is incident on the second optical coupler 20F via the reference optical system 20D.

[0086] These lights incident on the second optical coupler 20F, that is, the measurement light reflected from the fundus and the reference light, are interfered by the second optical coupler 20F to generate interference light. The interference light is received by the point sensor 20B. The image processing apparatus 17 operating under the control of the image processing unit 206 generates OCT images such as tomographic images and en-face images based on the OCT data detected by the point sensor 20B.

[0087] Here, an OCT image obtained by photographing with a photographing angle of 160 degrees or more at the internal irradiation angle, or an OCT image obtained by scanning the peripheral part of the fundus is referred to as a UWF-OCT image.

[0088] The image data of the UWF-OCT image is sent from the ophthalmic device 110 to the server 140 via a communication IF (not shown) and stored in the storage device.

[0089] In the present embodiment, the light source 20A is exemplified as a wavelength-sweeping type SS-OCT (Swept-Source OCT), but OCT systems of various methods such as SD-OCT (Spectral-Domain OCT) and TD-OCT (Time-Domain OCT) may also be used.

[0090] In the present embodiment, basically, the elastic modulus of the retinal blood vessels is calculated by the processes shown in FIGS. 4 and 8. However, in the present embodiment, instead of Full field OCT that collectively acquires OCT data of the fundus by collectively irradiating the measurement light to the fundus of the eye to be examined 12, OCT imaging is performed using point scanning that locally acquires OCT data. Therefore, it is necessary to accurately set the OCT scan position in step 502 of FIG. 4 and specify the first blood vessel region in step 902 of FIG. 8.

[0091] In this embodiment, the first OCT data and the second OCT data are acquired by performing tomographic imaging along the blood vessels in the retina. Therefore, the OCT scan position may be set by extracting the region where blood vessels exist from the OCT data obtained by separately performing an OCT scan on the entire fundus, or the OCT scan position may be set by extracting the region where blood vessels exist by using SLO data in combination. Alternatively, the OCT scan position may be set by angiography (angioplasty) using a contrast agent. Further, according to the specified OCT scan position, the irradiation position of the retina by the ultrasonic probe 120 may be controlled, and the OCT scan position may be scanned with focused ultrasonic waves. To scan the OCT scan position with focused ultrasonic waves, an actuator that adjusts the orientation of the ultrasonic probe 120 is controlled in synchronization with the scanning of the measurement light by the OCT scanner 24.

[0092] In step 902 of FIG. 8, a region including the intersection of blood vessels as shown in FIGS. 9A, 9B, 9C, and 9D may be preferentially specified as the first blood vessel region.

[0093] Then, as shown in step 910 of FIG. 8, the elastic modulus of the blood vessel is calculated based on the thickness of the blood vessel in the first blood vessel region and the thickness of the blood vessel in the second blood vessel region.

[0094] As described above, in this embodiment, by performing tomographic imaging along the blood vessels, the number of measurement points is reduced to enable high-speed imaging, and the measurement error due to the movement of the living body, which is a weakness of strain imaging, is reduced.

[0095] Further, in this embodiment, the elastic modulus of the retinal blood vessels can also be calculated by using an apparatus capable of performing OCT imaging by a point scan method using an inexpensive point sensor as compared with an apparatus capable of full field OCT. In addition, in SD-OCT, the elastic modulus of the retinal blood vessels can be measured by changing the detector from a point sensor to a detector composed of a spectrometer and a line sensor.

[0096] The image processing in each of the embodiments described above is merely an example. Therefore, it goes without saying that unnecessary steps may be deleted, new steps may be added, or the processing order may be changed within the scope not departing from the gist.

[0097] In each of the embodiments described above, image processing based on a software configuration using a computer is assumed, but the technology of the present disclosure is not limited thereto. For example, instead of a software configuration using a computer, image processing may be executed only by a hardware configuration such as an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). Part of the image processing may be executed by a software configuration, and the remaining processing may be executed by a hardware configuration.

Explanation of Signs

[0098] 12 Eye to be examined 14 Imaging device 16 Control device 17 Image processing device 20 OCT unit 20A Light source 20B Point sensor 20C Optical coupler 20D Reference optical system 20E Collimating lens 20F Optical coupler 22 Optical scanner 24 OCT scanner 100 Ophthalmic system 110 Ophthalmic device 116 Control device 119 Imaging optical system 120 Ultrasonic probe 130 Network 140 Server 150 Viewer 160 Light source 168 Cube beam splitter 190 Reference light 192 Measurement light 194 Interference light 200 OCT unit 204 OCT data acquisition section 206 Image processing section 208 Processing section 210 Ophthalmic device 300A Artery 300V Vein 302 Vessel wall

Claims

1. An ultrasonic irradiation unit that applies ultrasonic waves to the eye to be examined; A tomographic image acquisition unit that collectively acquires a tomographic image of the eye to be examined by a two-dimensional detector; A control unit that controls the ultrasonic irradiation unit and the tomographic image acquisition unit so as to acquire a first tomographic image of the eye to be examined in a state where the first ultrasonic wave of the first output is irradiated from the ultrasonic irradiation unit to the eye to be examined, and to acquire a second tomographic image of the eye to be examined in a state where the second ultrasonic wave of the second output different from the first output is irradiated from the ultrasonic irradiation unit to the eye to be examined; An image processing unit that specifies a first blood vessel region from the first tomographic image and a second blood vessel region from the second tomographic image, and calculates the elastic modulus of the blood vessels of the eye to be examined based on the first blood vessel region and the second blood vessel region; An ophthalmic apparatus comprising the above.

2. A blood vessel position specifying unit that specifies the position of retinal blood vessels from a retinal image of the eye to be examined; An ultrasonic irradiation unit that applies ultrasonic waves to a specific location of the eye to be examined; A light source that emits broadband light; A branching unit that branches the light emitted from the light source into measurement light and reference light for irradiating the fundus of the eye to be examined; An interference unit that generates interference light between the reflected light generated by reflection of the measurement light from the fundus of the eye to be examined and the reference light; A scanning unit that scans the retinal blood vessels specified by the blood vessel position specifying unit with the measurement light; A detection unit that detects the interference light and outputs a detection signal; An image processing unit that outputs a tomographic image of the eye to be examined based on the detection signal; A control unit that controls each of the ultrasonic irradiation unit, the light source, the interference unit, the scanning unit, the detection unit, and the image processing unit so as to acquire a first tomographic image of the eye to be examined in a state where the first ultrasonic wave of the first output is irradiated from the ultrasonic irradiation unit to the eye to be examined, and to acquire a second tomographic image of the eye to be examined in a state where the second ultrasonic wave of the second output different from the first output is irradiated from the ultrasonic irradiation unit to the eye to be examined, and calculates the elastic modulus of the blood vessels of the eye to be examined based on the first tomographic image and the second tomographic image; An ophthalmic apparatus comprising the above.

3. The ultrasonic irradiation unit operates in synchronization with the scanning unit to apply ultrasonic waves in accordance with the scanning position of the measurement light. The ophthalmic apparatus according to claim 2. The ophthalmic apparatus according to claim 2.

4. The first output is 0, and the second output is an output sufficient to constrict the blood vessels in the fundus. The ophthalmic apparatus according to any one of claims 1 to 3. The ophthalmic apparatus according to any one of claims 1 to 3.

5. The control unit obtains an elastic modulus of the blood vessel by dividing a first difference obtained from a first pressure at the time of irradiating the first ultrasonic wave and a second pressure at the time of irradiating the second ultrasonic wave by a second difference obtained from a first diameter of the blood vessel calculated from the first tomographic image and a second diameter of the blood vessel calculated from the second tomographic image. The ophthalmic apparatus according to any one of claims 1 to 4.

6. The blood vessel is a blood vessel of the retina. The ophthalmic apparatus according to any one of claims 1 to 5.

7. The ultrasonic wave is a focused ultrasonic wave. The ophthalmic apparatus according to any one of claims 1 to 6.

8. Collectively acquiring a first tomographic image of the eye to be examined by a two-dimensional detector in a state where the first ultrasonic wave is irradiated to the eye to be examined with a first output from an ultrasonic wave irradiation unit; Collectively acquiring a second tomographic image of the eye to be examined by the two-dimensional detector in a state where a second ultrasonic wave having a second output different from the first output is irradiated to the eye to be examined from the ultrasonic wave irradiation unit; Identifying a first blood vessel region from the first tomographic image and a second blood vessel region from the second tomographic image, and calculating an elastic modulus of the blood vessel of the eye to be examined based on the first blood vessel region and the second blood vessel region; An image processing method including.

9. Identifying the position of the retinal blood vessel from the retinal image of the eye to be examined; Irradiating a measurement light obtained by branching a reference light from a broadband light emitted from a light source and a first ultrasonic wave having a first output from an ultrasonic wave irradiation unit to the position of the retinal blood vessel of the eye to be examined, respectively; Generating interference light between reflected light generated by reflecting the measurement light irradiated to the eye to be examined in the eye to be examined and the reference light; Detecting the interference light and outputting a first tomographic image of the eye to be examined; Irradiating the measurement light and a second ultrasonic wave having a second output different from the first output from the ultrasonic wave irradiation unit to the position of the retinal blood vessel of the eye to be examined, respectively; Generating interference light between reflected light generated by reflecting the measurement light irradiated to the eye to be examined in the eye to be examined and the reference light; Detecting the interference light and outputting a second tomographic image of the eye to be examined; Calculating an elastic modulus of the blood vessel of the eye to be examined based on the first tomographic image and the second tomographic image; An image processing method including.

10. The first output is 0, and the second output is an output sufficient to contract the blood vessel of the eye to be examined. The image processing method according to claim 8 or claim 9.

11. The elastic modulus of the blood vessels in the fundus of the eye to be examined is calculated by dividing a first difference between a first pressure by the first ultrasonic wave and a second pressure by the second ultrasonic wave by a second difference between a first diameter of the blood vessel calculated from the first tomographic image and a second diameter of the blood vessel calculated from the second tomographic image. The image processing method according to any one of claims 8 to 10.

12. The blood vessels are retinal blood vessels. The image processing method according to any one of claims 8 to 11.

13. Each of the first ultrasonic wave and the second ultrasonic wave is a focused ultrasonic wave. The image processing method according to any one of claims 8 to 12, characterized in that.

14. An ultrasonic irradiation unit that applies ultrasonic waves to the eye to be examined, A tomographic image acquisition unit that collectively acquires tomographic images of the eye to be examined by a two-dimensional detector, A control unit that acquires a first tomographic image of the eye to be examined with the ultrasonic irradiation unit turned off and acquires a second tomographic image of the eye to be examined with the ultrasonic irradiation unit irradiating the eye to be examined with ultrasonic waves, and controls the ultrasonic irradiation unit and the tomographic image acquisition unit, An image processing unit that specifies a first blood vessel region from the first tomographic image and a second blood vessel region from the second tomographic image, and calculates the elastic modulus of the blood vessels in the eye to be examined based on the first blood vessel region and the second blood vessel region, An ophthalmic device including.

15. A blood vessel position specifying unit that specifies the position of retinal blood vessels from a retinal image of the eye to be examined, An ultrasonic irradiation unit that applies ultrasonic waves to a specific location of the eye to be examined, A light source that emits broadband light, A branching unit that branches the light emitted from the light source into measurement light and reference light for irradiating the fundus of the eye to be examined, An interference unit that generates interference light between reflected light generated by reflection of the measurement light on the fundus of the eye to be examined and the reference light, A scanning unit that scans the retinal blood vessels specified by the blood vessel position specifying unit with the measurement light, A detection unit that detects the interference light and outputs a detection signal, An image processing unit that outputs a tomographic image of the eye to be examined based on the detection signal, A control unit that acquires a first tomographic image of the eye to be examined with the ultrasonic irradiation unit turned off and acquires a second tomographic image of the eye to be examined with the ultrasonic irradiation unit irradiating the eye to be examined with ultrasonic waves, controls the ultrasonic irradiation unit, and calculates the elastic modulus of the blood vessels in the eye to be examined based on the first tomographic image and the second tomographic image, An ophthalmic device including.

16. The blood vessels are blood vessels in the fundus of the eye, The ophthalmic apparatus according to claim 14 or claim 15, wherein the control unit generates an image in which a display form of a blood vessel portion of a fundus image is changed based on the elastic modulus.

Images