Ophthalmologic apparatus 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 technology]

[0002] Patent Document 1 discloses an invention for predicting the risk of developing glaucoma in a subject's eye. There is a need to measure the state of blood vessels in the fundus in order to predict diseases such as glaucoma in the subject's eye. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 8,137,271 Summary of the Invention

[0004] An ophthalmic device according to a first aspect of the disclosed technology includes an ultrasound irradiation unit that applies ultrasound to a test eye, a tomographic image acquisition unit that acquires a tomographic image of the test eye, and a control unit that controls the ultrasound irradiation unit and the tomographic image acquisition unit to acquire a first tomographic image of the test eye while irradiating the test eye with a first ultrasound at a first output from the ultrasound irradiation unit, and to acquire a second tomographic image of the test eye while irradiating the test eye with a second ultrasound at a second output different from the first output from the ultrasound irradiation unit, and calculates the elastic modulus of blood vessels in the test eye based on the first tomographic image and the second tomographic image.

[0005] An image processing method according to a second aspect of the disclosed technology includes obtaining a first tomographic image of the test eye while irradiating the test eye with a first ultrasonic wave at a first output from an ultrasonic irradiation unit, obtaining a second tomographic image of the test eye while irradiating the fundus with a second ultrasonic wave at a second output different from the first output from the ultrasonic irradiation unit, and calculating the elastic modulus of blood vessels in the test eye based on the first tomographic image and the second tomographic image. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a block diagram of an ophthalmologic system 100 according to a first embodiment. [Figure 2] 1 is a diagram showing the overall configuration of an ophthalmologic apparatus 110 according to a first embodiment. [Figure 3] 10 is an explanatory diagram of functions realized by an image processing program in a CPU 15A of the ophthalmologic apparatus 110. FIG. [Figure 4] 4 is a flowchart showing a process for measuring elasticity of retinal blood vessels in the first embodiment of the present invention. [Figure 5] 2 is a schematic diagram showing irradiation of an eye 12 to be inspected with ultrasound. FIG. [Figure 6] 3 is an explanatory diagram showing the effect of ultrasonic irradiation on the retinal blood vessels of the subject's eye 12. FIG. [Figure 7] FIG. 1 is an explanatory diagram of strain imaging showing differences in Young's modulus, blood vessel displacement, and blood vessel strain due to differences in hardening of the blood vessel wall. [Figure 8] 5 is a flowchart showing the process of calculating the elastic modulus of a blood vessel in step 512 of FIG. 4. [Figure 9A] This is a schematic diagram showing a state in which a vein is curved like an arch because an artery that has expanded peripherally due to arteriosclerosis pulls the vein through the vascular wall. [Figure 9B] This is a schematic diagram showing a state in which arteriosclerosis progresses and the opaque arterial wall hides the vein at the crossing, making it appear as if blood flow in the vein has been cut off. [Figure 9C] This is a schematic diagram showing a condition in which the arterial wall of an arteriosclerotic artery obscures the blood flow in the vein, making the tip of the vein at the crossing appear to be narrowed. [Figure 9D] This is a schematic diagram showing how arterial walls, thickened by arteriosclerosis, obstruct blood flow in veins. [Figure 10] 1 is a schematic diagram showing a display image displayed on the display of a viewer 150. FIG. [Figure 11] FIG. 2 is a block diagram showing the configuration of an ophthalmologic apparatus 210 according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

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

[0008] The ophthalmologic apparatus 110 is an apparatus for photographing the subject's eye, photographing the posterior and anterior segments of the subject's eye and acquiring fundus images and anterior segment images. The ophthalmologic apparatus 110 is equipped with an optical coherence tomography (OCT) for acquiring tomographic images of the subject's eye. The apparatus may be an apparatus that combines not only OCT but also other modalities such as a fundus camera and a scanning laser ophthalmoscope (SLO).

[0009] The server 140 stores images of the subject's eye captured by the ophthalmologic apparatus 110 in association with the patient's ID. The viewer 150 displays data acquired by the server 140 (images of the subject's eye, analysis results for assisting diagnosis, etc.).

[0010] The ophthalmic apparatus 110, the server 140, and the viewer 150 are connected to each other via a network 130. The viewer 150 is a client in a client-server system, and multiple viewers 150 are connected via the network. Furthermore, multiple servers 140 may also be connected via the network to ensure system redundancy. Alternatively, if the ophthalmic apparatus 110 has an image processing function and the viewer 150 has an image viewing function, the ophthalmic apparatus 110 can acquire, process, and view fundus images in a standalone state. Furthermore, if the server 140 has the viewer 150 has an image viewing function, the configuration of the ophthalmic apparatus 110 and the server 140 can acquire, process, and view fundus images.

[0011] In addition, other ophthalmic devices (examination devices for visual field measurement, intraocular pressure measurement, etc.) and diagnostic support devices that perform 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, the configuration of the ophthalmic device 110 will be described with reference to Fig. 2. Note that the horizontal direction when the ophthalmic device 110 is placed on a horizontal plane is referred to as the "X direction," the direction perpendicular to the horizontal plane is referred to as the "Y direction," and the direction connecting the center of the pupil 27 of the anterior segment of the subject's eye 12 and the center O of the eyeball is referred to as the "Z direction." Therefore, the X direction, Y direction, and Z direction are perpendicular to each other.

[0013] The ophthalmologic apparatus 110 includes an imaging device 14 and a control device 116. The imaging device 14 is configured with an SLO unit 18 and an OCT unit 200. A two-dimensional fundus image acquired by the SLO unit 18 is referred to as an SLO image. Furthermore, a tomographic image or a front image (en-face image) of the retina created based on OCT data acquired by the OCT unit 200 is referred to as an OCT image. An OCT image corresponds to a "tomographic image" in the technology of the present disclosure.

[0014] The controller 116 comprises a computer having a central processing unit (CPU) 16A, random access memory (RAM) 16B, read-only memory (ROM) 16C, and input / output (I / O) ports 16D.

[0015] The control device 116 includes an input / display device 16E connected to the CPU 16A via an I / O port 16D. The input / display device 16E has a graphic user interface that displays an image of the subject's eye 12 and receives various instructions from the user. An example of the graphic user interface is a touch panel display.

[0016] The control device 116 also includes an image processing device 17 connected to an I / O port 16D. The image processing device 17 generates an image of the subject's eye 12 based on data obtained by the photographing device 14, and executes various image processing operations in cooperation with the CPU 16A. The control device 116 is connected to a network 130 via a communication interface 16F.

[0017] 2, the control device 116 of the ophthalmic apparatus 110 includes the input / display device 16E, but the technology of the present disclosure is not limited to this. For example, the control device 116 of the ophthalmic apparatus 110 may not include the input / display device 16E, but may include an input / display device that is physically independent from the ophthalmic apparatus 110.

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

[0019] The optical scanner 22 performs two-dimensional scanning in the X and Y directions with the light emitted from the SLO unit 18. The optical scanner 22 may be any optical element that can deflect a light beam, such as a polygon mirror or a galvanometer mirror, or a combination thereof.

[0020] The wide-angle optical system 30 guides light from the SLO unit 18 to the subject's eye 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 system combining concave mirrors and lenses. By using a wide-angle optical system using an elliptical mirror or a wide-angle lens, it becomes possible to photograph the retina not only at the center of the fundus but also at the peripheral part of the fundus.

[0021] When a system including an elliptical mirror is used, the system using the 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 of the fundus over a wide field of view (FOV) 12A. The FOV 12A indicates the range that can be photographed by the imaging device 14. The FOV 12A can be expressed as a field of view. In this embodiment, the field of view can be defined by an internal illumination angle and an external illumination angle. The external illumination angle is the illumination angle of the light beam irradiated from the ophthalmic device 110 to the subject's eye 12, determined with the pupil 27 as the reference. The internal illumination angle is the illumination angle of the light beam irradiated to the fundus, determined with the center O of the eyeball as the reference. The external illumination angle and the internal illumination angle correspond to each other. For example, if the external illumination angle is 120 degrees, the internal illumination angle corresponds to approximately 160 degrees. In this embodiment, the internal illumination angle is 200 degrees.

[0023] Here, an SLO fundus image captured at an internal illumination angle of 160 degrees or more is referred to as a UWF-SLO fundus image. UWF stands for Ultra Wide Field. The wide-angle optical system 30, which provides an ultra-wide field of view (FOV) of the fundus, can capture images of the area from the posterior pole of the fundus of the subject's eye 12 beyond the equator, enabling the capture of structures present in the peripheral area of ​​the fundus, such as retinal blood vessels.

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

[0025] The SLO unit 18 includes a B (blue light) light source 40, a G (green light) light source 42, an R (red light) light source 44, and an IR (infrared (e.g., near-infrared) light) light source 46, as well as optical systems 48, 50, 52, 54, and 56 that reflect or transmit the light from the light sources 40, 42, 44, and 46 and guide them into a single optical path. The optical systems 48 and 56 are mirrors, and the optical systems 50, 52, and 54 are beam splitters. The B light is reflected by the optical system 48, passes through the optical system 50, and is reflected by the optical system 54; the G light is reflected by the optical systems 50 and 54; the R light is transmitted through the optical systems 52 and 54; and the IR light is reflected by the optical systems 52 and 56 and is each guided into a single optical path.

[0026] The SLO unit 18 is configured to be switchable between a light source emitting laser light of different wavelengths or a combination of light sources emitting laser light of different wavelengths, such as a mode emitting R light and G light and a mode emitting infrared light. In the example shown in FIG. 2 , four light sources are provided: 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 of white light, and may emit light in various modes, such as a mode emitting G light, R light, and B light, or a mode emitting only white light.

[0027] Light incident on the photographing optical system 19 from the SLO unit 18 is scanned in the X and Y directions by the optical scanner 22. The scanning light passes through the wide-angle optical system 30 and the pupil 27 and is irradiated onto the fundus. The light reflected by the fundus passes through the wide-angle optical system 30 and the optical scanner 22 and is incident on the SLO unit 18.

[0028] The SLO unit 18 includes a beam splitter 64 that reflects B light and transmits all light except B light from the posterior segment (fundus) of the subject's eye 12, and a beam splitter 58 that reflects G light and transmits all light except G light from the light that has passed through the beam splitter 64. The SLO unit 18 includes a beam splitter 60 that reflects R light and transmits all light except R light from the light that has passed through the beam splitter 58. The SLO unit 18 includes a beam splitter 62 that reflects IR light from the light that has passed through the beam splitter 60. The SLO unit 18 includes a B light detecting element 70 that detects B light reflected by the beam splitter 64, a G light detecting element 72 that detects G light reflected by the beam splitter 58, an R light detecting element 74 that detects R light reflected by the beam splitter 60, and an IR light detecting element 76 that detects IR light reflected by the beam splitter 62.

[0029] 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 incident light is transmitted through the beam splitter 58 in the case of R light, reflected by the beam splitter 60, and received by the R light detection element 74. The incident light is transmitted through the beam splitters 58 and 60, 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, which operates under the control of the CPU 16A, generates a UWF-SLO image using 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] The control device 116 also controls the light sources 40, 42, 44 to emit light simultaneously. By simultaneously photographing the fundus of the subject's eye 12 with B light, G light, and R light, a G-color fundus image, a R-color fundus image, and a B-color fundus image, each of which 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, 44 to emit light simultaneously, and by simultaneously photographing the fundus of the subject's eye 12 with G light and R light, a G-color fundus image and a R-color fundus image, each of which 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 OCT unit 200 shown in Fig. 2. The OCT unit 200 is a device capable of full-field OCT, which acquires fundus OCT data all at once by irradiating the fundus of the subject's eye 12 with measurement light all at once. The OCT unit 200 can acquire OCT data of structures present in the peripheral part of the fundus, such as retinal blood vessels, and can obtain tomographic images of the retinal blood vessels and the 3D structure of the retinal blood vessels by image processing the OCT data.

[0032] The configuration of the optical system of the OCT unit 200 will be described with reference to Fig. 2. The OCT unit 200 shown in Fig. 2 includes a wavelength sweep 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 collimate the light beam and expand its beam diameter, a cube beam splitter 168 that splits the light beam into measurement light 192 and reference light 190 and causes them to interfere with each other to generate interference light 194, a wave plate 170 that polarizes the reference light 190, and a reflecting mirror 172 that totally reflects the reference light 190 with a reflecting surface that is perpendicular to the traveling direction of the reference light 190.

[0033] 2 defines the traveling direction of the light beam output from the light source 160 as the Z direction, and the vibration plane of the light beam perpendicular to the Z direction as the XY plane. The X and Y directions are defined so as to coincide with the vibration plane of the electric field component and the vibration plane of the magnetic field component of the light beam. The Z direction is defined as the traveling direction of the measurement light 192 toward the subject's eye 12, and is also defined as the measurement depth direction of the subject's eye 12.

[0034] The polarizing plate 162 is a polarizing element made of a linear polarizer for aligning the polarization direction of the light beam from the light source 160. In this embodiment, the polarizing plate 162 is configured to transmit vibration components in angular directions that form 45° with respect to the X-axis and Y-axis of the XYZ coordinate system. As a result, the light beam that has passed through the polarizing plate 162 has linear polarization at an angle of 45°. Therefore, the polarization components of the light beam in the X-axis and Y-axis directions each have the same amplitude. In other words, the P-polarized component and S-polarized component of the light beam each have the same amplitude.

[0035] The cube beam splitter 168 acts to split the parallelized linearly polarized light beam into measurement light 192 directed toward the subject's eye 12 and reference light 190 directed toward the reflecting mirror 172. The cube beam splitter 168 reflects a portion (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 subject's eye 12 via the objective lens 176.

[0036] The cube beam splitter 168 reflects a portion of the measurement light 192 that has passed through the test eye 12 and transmits a portion of the reference light 190 that has passed through the reflecting mirror 172, causing the measurement light 192 and the reference light 190 to interfere with each other and generate interference light 194.

[0037] Wave plate 170 is a polarization conversion element that converts the polarization characteristics of reference light 190, which has been linearly polarized by polarizer 162. In this embodiment, a ⅛ wave plate is used as wave plate 170. As a result, a phase difference of π / 4 is imparted between the P-polarized and S-polarized components of reference light 190 when it passes through wave plate 170. The reference light 190 is imparted with the phase difference when it travels from cube beam splitter 168 toward reflecting mirror 172 and when it is reflected by reflecting mirror 172 and re-enters cube beam splitter 168, resulting in a phase difference of π / 2. Therefore, because wave plate 170 acts in the same way as a ¼ wave plate on reference light 190 that is linearly polarized at 45°, the reference light 190 re-entering cube beam splitter 168 is converted into circularly polarized light.

[0038] The interference light 194 is generated by interference between 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 processing device 17 of the control device 116 performs image processing based on the detection signals output from the CCD 182, and performs processing to form a tomographic image of the subject's eye 12. The OCT unit 200 is capable of full-field OCT, which acquires an XY tomographic image of any depth region of the subject's eye 12 in a single shot, i.e., over the entire field of view.

[0040] The ophthalmologic apparatus 110 in this embodiment also includes an ultrasonic probe 120 that irradiates the subject's eye with ultrasonic waves. The ultrasonic probe 120 applies pressure to the subject's eye 12 by acoustic radiation force under the control of the control device 116. The ultrasonic waves compress the subject's eye 12, thereby compressing the blood vessels of the subject's eye.

[0041] The retinal blood vessels are compressed by irradiating the fundus with ultrasound generated from the ultrasound probe 120. The ultrasound probe may be adjusted to converge on the retina, or may be configured to generate focused ultrasound so that the ultrasound is irradiated on the retinal blood vessels whose elasticity is to be measured.

[0042] FIG. 4 is a flowchart showing the process of measuring the elastic modulus of retinal blood vessels in this embodiment. A case where the process shown in FIG. 4 is executed by the control device 116 of the ophthalmologic apparatus 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 has an OCT data acquisition function, an image processing function, and a processing function. When the CPU 16A executes a program having these 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 the function achieved by cooperation between the CPU 16A and the image processing device 17. The program is a computer program product for image processing, the computer program product including a computer-readable storage medium that is not a temporary signal, the computer-readable storage medium storing the program, the program causing a computer to execute the steps of acquiring a first tomographic image of the subject's eye with an ultrasound irradiation unit turned off, acquiring a second tomographic image of the subject's eye with ultrasound irradiated from the ultrasound irradiation unit to the subject's eye, and calculating the elastic modulus of the blood vessels of the subject's eye based on the first tomographic image and the second tomographic image. In this embodiment, the process shown in FIG. 4 is realized by executing the program.

[0043] In step 500, the OCT data acquisition section 204 controls the OCT unit 200 to perform alignment with the subject's eye 12, focus adjustment, etc., to bring the OCT data of the fundus of the subject's eye 12 into a state where it is possible to acquire the data.

[0044] In step 502, the OCT data acquisition unit 204 sets the OCT scan position. In this embodiment, full-field OCT is performed to acquire OCT data for a predetermined area of ​​the fundus all at once. The predetermined area 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 so that the optic disc is at the center of the predetermined area. Alternatively, the position of a fixation target (not shown) may be changed to change the orientation of the subject's eye 12 relative to the optical axis, and the position of the predetermined area may be set to the periphery of the fundus.

[0045] In step 504, the OCT data acquisition unit 204 acquires first OCT data for the set OCT scan position without operating (turning off) the ultrasound probe 120. The first OCT data is OCT data for a predetermined region in a state where no ultrasound is irradiated. The processing unit 208 then stores and holds the acquired first OCT data in RAM 16B.

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

[0047] 6 is an explanatory diagram showing the effect of ultrasonic irradiation on the fundus of the subject's eye 12. As shown in Fig. 6, ultrasonic irradiation of the fundus presses the vascular walls 302 of the retinal blood vessels, compressing the retinal blood vessels 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 the differences in Young's modulus, blood vessel diameter displacement, and blood vessel strain due to differences in hardening when soft and hard objects (blood vessels) are mixed. A higher Young's modulus indicates more advanced hardening of the blood vessel wall. Furthermore, the greater the displacement or strain of the object due to the action of stress, the greater the Young's modulus value. In this embodiment, the Young's modulus, which indicates the elasticity of the retinal blood vessels, is calculated based on OCT data obtained when ultrasound is irradiated onto the fundus of the subject's eye 12 and OCT data obtained without ultrasound irradiation. That is, in the OCT data obtained with ultrasound irradiation, the harder the blood vessel wall (the higher the Young's modulus), the smaller the blood vessel wall strain, and the softer the blood vessel wall (the smaller the Young's modulus), the greater the blood vessel wall strain. Therefore, by measuring the magnitude of strain from the OCT data obtained when ultrasound is irradiated onto the fundus of the subject's eye 12 and the OCT data obtained without ultrasound irradiation, the Young's modulus of the blood vessel wall at the time of measurement can be calculated.

[0049] In step 508, the OCT data acquisition unit 204 acquires second OCT data at the set OCT scan position while ultrasound is being irradiated to the subject's eye 12. 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 a state where ultrasound is irradiated. 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 (turns it off), and the irradiation of ultrasonic waves is stopped.

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

[0051] Fig. 8 is a flowchart showing the process of calculating the elastic modulus of a blood vessel 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 a CPU provided in the server 140.

[0052] In step 902, the image processing unit 206 identifies a first vascular region, which is a target region for calculating the elastic modulus of blood vessels. The first vascular region may be identified by extracting a region where blood vessels exist using the first OCT data, or by extracting a region where blood vessels exist using SLO data in combination. Alternatively, the region may be identified by angiography (angiography) using a contrast agent. For example, since the intersection of retinal blood vessels in the fundus is a site where vitreous hemorrhage or retinal detachment is likely to occur, a region including the intersection of blood vessels may be preferentially identified as the first vascular region. Furthermore, since this embodiment enables full-field OCT, which simultaneously irradiates the fundus of the subject's eye 12 with measurement light to simultaneously acquire OCT data of the fundus, the entire fundus may be the first vascular region.

[0053] 9A, 9B, 9C, and 9D are schematic diagrams showing examples of arteriovenous crossing. Fig. 9A shows a state in which artery 300A, which has been extended peripherally due to arteriosclerosis, pulls vein 300V through the vascular wall, causing vein 300V to curve in an arch shape at the intersection with artery 300A.

[0054] Figure 9B shows a state in which arteriosclerosis has progressed and the vascular walls have thickened, causing the vascular wall of artery 300A to obscure vein 300V at the crossing point (because the measurement light is blocked by the vascular wall of artery 300A and cannot reach vein 300V), making it appear as if blood flow in vein 300V has stopped.

[0055] Also, as shown in FIG. 9C, there is a situation where the vascular wall of artery 300A with advanced arteriosclerosis hides the blood flow in vein 300V, making the tip of vein 300V at the crossing appear to be narrowed.

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

[0057] In this embodiment, the regions in the states illustrated in FIGS. 9A, 9B, 9C, and 9D may be preferentially identified as the first vascular region.

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

[0059] In step 906, a second vascular region in the second OCT data is identified. The second vascular region is a region in the second OCT data that corresponds to the first vascular region in the first OCT data.

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

[0061] In step 910, the elastic modulus of the blood vessel is calculated. 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. In this embodiment, if the difference between 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 is the strain amount ε and the pressure (stress) that the ultrasound probe 120 exerts on the fundus of the subject's eye 12 is σ, Young's modulus E, which indicates the elastic modulus of the blood vessel, is calculated by the following formula (1):

[0062] E=σ / ε …(1)

[0063] In step 912, the data on the elastic modulus of the blood vessel is saved in the storage device of server 140, and the process shown in Fig. 8 is terminated. Then, the process returns to step 514 in Fig. 4. The data on the elastic modulus of the blood vessel may be data that combines the position of a pixel in the blood vessel and the elastic modulus at that position. Furthermore, the data may include pixel brightness, blood vessel diameter, etc.

[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] The display screen 500 will be described in detail below. The display screen 500 has an information display area 502, an image display area 504, and an elasticity information display area 506. The information display area 502 has 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. Based on information received from the server 140, the information display area 502 displays information in each of the display areas, 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 fundus images, etc. In FIG. 10 , a fundus image 530 acquired by full-field OCT and tomographic images 532 and 534 of blood vessels at the position indicated by arrow 536 are displayed. The blood vessels displayed in the fundus image 530 are displayed in different ways, such as by being color-coded according to their elasticity. The elasticity of a healthy retina is generally about 10 kPa. The elasticity of retinal blood vessels varies to a certain extent, from about 10 kPa to 30 kPa. The fundus image 530 may be an SLO image rather than an en-face image generated from OCT data. In this case, image processing may be performed, such as registering the SLO image and the en-face image and color-coding the blood vessels in the SLO image using elasticity data.

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

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

[0069] The elasticity information display area 506 displays information such as the elasticity of the blood vessel 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.

[0070] As described above, in this embodiment, focused ultrasound is irradiated onto the retina of the subject's eye 12, and the elastic modulus of the blood vessels can be calculated based on the amount of change in blood vessel diameter before and after ultrasound irradiation measured by OCT. Furthermore, it is possible to measure the elastic modulus of not only the blood vessels at the fundus but also the blood vessels in the anterior segment (near the ciliary body, etc.) in the same way as the blood vessels at the fundus.

[0071] Measurement of retinal vascular elasticity is required for early detection of intraocular diseases such as retinal vein occlusion, vitreous hemorrhage, and retinal detachment. In particular, early detection of potential lesions based on the elasticity of retinal blood vessels is required in the optic disc, near the macula, or at the arteriovenous intersection.

[0072] Blood vessel elasticity measurements are generally performed using invasive techniques, in which a probe is inserted into the subject's eye 12, but this places a significant burden on the patient. In addition, strain imaging, a type of elasticity measurement method, is easily affected by biological movement, so high speed is required for measurements.

[0073] In this embodiment, full-field OCT is used to simultaneously acquire OCT data for a predetermined region of the fundus, allowing elastic modulus measurements to be performed by calculating the elastic modulus of multiple blood vessels present in the predetermined region. This is because, when OCT data is acquired by two-dimensional scanning using a laser beam with a point sensor and a scanner, the state of the blood vessels may change during the two-dimensional scanning due to factors such as pulsation, heartbeat, and involuntary eye movements. With full-field OCT, the first OCT data for the predetermined region is acquired at the same time t1, and the first OCT data is not acquired at different times depending on the location (the second OCT data is also acquired at the same time t2). Therefore, full-field OCT can measure elastic modulus more accurately than two-dimensional scanning.

[0074] Furthermore, the elastic modulus of a specific blood vessel may be calculated from among multiple blood vessels in the specified region, and further, the elastic modulus of a blood vessel at a specific position (for example, a blood vessel position specified by the user) may be calculated.

[0075] In this embodiment, strain imaging is performed non-invasively by externally irradiating the fundus of the subject eye 12 with focused ultrasound, and high-speed imaging is enabled by applying full-field OCT technology, thereby reducing measurement errors due to biological movement, which is a weakness of strain imaging.

[0076] In the present embodiment, ultrasound is not irradiated to the subject's eye 12 when the first OCT data is acquired, and ultrasound is irradiated to the subject's eye 12 when the second OCT data is acquired. However, this is not limiting. For example, ultrasound may be irradiated to the subject's eye 12 at a first output when the first OCT data is acquired, and ultrasound may be irradiated to the subject's eye 12 at a second output different from the first output when the second OCT data is acquired. In such a case, in the above-described formula (1), the pressure (stress) σ acting on the fundus of the subject's eye 12 by the ultrasound probe 120 becomes a value corresponding to the difference between the first output and the second output. Furthermore, with this configuration, if ultrasound is not irradiated to the subject's eye 12 when the first OCT data is acquired, the first output is set to 0.

[0077] 4 and 8 are performed by the ophthalmic apparatus 110. However, they may also be performed by the server 140 after the first OCT data and the second OCT data are acquired by the ophthalmic apparatus 110. 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 that visualizes the elastic modulus of the retina is generated. An image signal of the generated display screen 500 is transmitted to the viewer 150 or the like via the network 130. Thus, a user of the viewer 150 can view the display screen 500, and information that supports diagnosis of the subject's eye can be displayed.

[0078] The retinal elasticity is visualized by the CPU of the server 140 executing the image processing program. The CPU of the server 140 executes the image processing program corresponding to steps 512 to 518 of the flowchart in Fig. 4, and 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 ophthalmologic apparatus 110.

[0079] [Second embodiment] Next, a second embodiment of the present invention will be described in detail with reference to FIG. 11. This embodiment differs from the first embodiment in that it uses an OCT unit that scans the subject's eye using point scanning, and the imaging optical system 119 includes an OCT scanner 24 for point scanning. However, since the other configurations are the same as those of the first embodiment, the same components are assigned the same reference numerals and detailed descriptions are omitted. Point scanning is a scanning method in which laser light is irradiated onto a single point on the subject's eye, and reflected light from the subject's eye is received by a point sensor. This is a scanning method in which a predetermined area of ​​the subject's eye is imaged by scanning with laser light.

[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 subject's eye 12.

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

[0082] The OCT unit 20 is an OCT unit capable of point scanning. OCT imaging using point scanning is achieved by the control device 16, OCT unit 20, and imaging optical system 119 shown in FIG. 11. The ophthalmologic apparatus 210 is equipped with a wide-angle optical system 30, which enables OCT imaging of the peripheral part of the fundus, similar to the above-mentioned SLO fundus image capture. In other words, the wide-angle optical system 30, which provides an ultra-wide field of view (FOV) of the fundus, can perform OCT imaging of the area from the posterior pole of the fundus of the subject's eye 12 beyond the equator. OCT data of structures present in the peripheral part of the fundus, such as retinal blood vessels, can be acquired, and tomographic images of the retinal blood vessels and the 3D structure of the retinal blood vessels can be obtained by image processing the OCT data.

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

[0084] Light emitted from the light source 20A is branched by the first optical coupler 20C. One of the branched beams is collimated by the collimating lens 20E as measurement light, and then two-dimensionally scanned in the X and Y directions by the OCT scanner 24 before entering the imaging optical system 19. The measurement light passes through the wide-angle optical system 30 and the pupil 27 and is irradiated onto the fundus. The measurement light reflected by the fundus passes through the wide-angle optical system 30 and enters the OCT unit 20, then passes through the collimating lens 20E and the first optical coupler 20C and enters the second optical coupler 20F. The OCT scanner 24 may be any optical element capable of deflecting a light beam, such as a polygon mirror or a galvanometer mirror. A combination of these elements may also be used.

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

[0086] The light beams incident on the second optical coupler 20F, i.e., the measurement light beam reflected from the fundus and the reference light beam, interfere with each other to generate interference light. The interference light beam is received by the point sensor 20B. The image processing device 17, which operates 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 capturing an image at an internal illumination angle of 160 degrees or more, or an OCT image obtained by scanning the peripheral part of the fundus, is referred to as a UWF-OCT image.

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

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

[0090] In this embodiment, the elastic modulus of the retinal blood vessels is calculated basically by the processing shown in Fig. 4 and Fig. 8. However, in this embodiment, OCT imaging is performed using point scanning, which acquires OCT data locally, rather than full-field OCT, which acquires OCT data of the fundus oculi collectively by irradiating the fundus oculi 12 with measurement light all at once, and therefore it is necessary to set the OCT scan position in step 502 in Fig. 4 and identify the first blood vessel region in step 902 in Fig. 8 with high accuracy.

[0091] In this embodiment, the first OCT data and the second OCT data are acquired by capturing a tomographic image along the blood vessels in the retina. Therefore, the OCT scan position may be set by extracting the blood vessel region from the OCT data obtained by separately scanning the entire fundus. Alternatively, the OCT scan position may be set by extracting the blood vessel region using SLO data in addition. Alternatively, the OCT scan position may be set by angiography using a contrast agent. Furthermore, the irradiation position of the retina by the ultrasound probe 120 may be controlled according to the identified OCT scan position, and the OCT scan position may be scanned with focused ultrasound. To scan the OCT scan position with focused ultrasound, an actuator that adjusts the orientation of the ultrasound 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 a crossing portion of blood vessels as shown in FIGS. 9A, 9B, 9C, and 9D may be preferentially identified 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 blood vessel size in the first blood vessel region and the blood vessel size in the second blood vessel region.

[0094] As described above, in this embodiment, by capturing tomographic images along blood vessels, the number of measurement points is reduced, enabling high-speed imaging, and reducing measurement errors due to biological movement, which is a weakness of strain imaging.

[0095] In this embodiment, the elasticity of retinal blood vessels can be calculated using an apparatus capable of OCT imaging by a point scanning method using a point sensor, which is less expensive than an apparatus capable of full-field OCT. Furthermore, in SD-OCT, the elasticity of retinal blood vessels can be measured by changing the detector from a point sensor to one consisting of a spectroscope and a line sensor.

[0096] The image processing in each embodiment 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, without departing from the spirit of the invention.

[0097] In the above-described embodiments, image processing is assumed to be performed by a software configuration using a computer, but the technology of the present disclosure is not limited to this. For example, instead of a software configuration using a computer, image processing may be performed 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 performed by a software configuration, and the remaining part may be performed by a hardware configuration. [Explanation of symbols]

[0098] 12 Examined eye 14 Imaging equipment 16 Control device 17 Image processing device 20 OCT units 20A light source 20B Point Sensor 20C Optical Coupler 20D reference optics 20E Collimating Lens 20F Optical Coupler 22 Optical Scanner 24 OCT scanner 100 Ophthalmology Systems 110 Ophthalmological equipment 116 Control device 119 Photographic optical system 120 Ultrasound Probe 130 Network 140 servers 150 viewers 160 light source 168 Cube Beam Splitter 190 Reference light 192 Measurement Light 194 Interferometric Light 200 OCT units 204 OCT data acquisition unit 206 Image Processing Unit 208 Processing section 210 Ophthalmological equipment 300A artery 300V venous 302 Blood vessel wall

Claims

[Claim 1] an ultrasound irradiation unit that applies ultrasound to the subject's eye; a tomographic image acquisition unit for acquiring a tomographic image of the subject's eye; a control unit that controls the ultrasound irradiation unit and the tomographic image acquisition unit to acquire a first tomographic image of the subject's eye while irradiating the subject's eye with a first ultrasound wave of a first output from the ultrasound irradiation unit, and to acquire a second tomographic image of the subject's eye while irradiating the subject's eye with a second ultrasound wave of a second output different from the first output from the ultrasound irradiation unit, and calculates elasticity of blood vessels of the subject's eye by comparing the first tomographic image with the second tomographic image; 1. An ophthalmic device comprising:

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