JP7711369B2 - Ophthalmic device and image processing method - Google Patents

Description

The present invention relates to an ophthalmic device and an image processing method.

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.

U.S. Pat. No. 8,137,271

The ophthalmic device of the 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 in a state where a first ultrasound is irradiated to the test eye from the ultrasound irradiation unit at a first output, and to acquire a second tomographic image of the test eye in a state where a second ultrasound is irradiated to the test eye from the ultrasound irradiation unit at a second output different from the first output, and calculates the elasticity of blood vessels of the test eye based on the first tomographic image and the second tomographic image.

The image processing method of the 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 of the test eye based on the first tomographic image and the second tomographic image.

1 is a block diagram of an ophthalmologic system 100 according to a first embodiment. 1 is a diagram showing an overall configuration of an ophthalmic apparatus 110 according to a first embodiment. 10 is an explanatory diagram of functions realized by an image processing program in a CPU 15A of the ophthalmic apparatus 110. FIG. 4 is a flowchart showing a process of measuring elasticity of a retinal blood vessel in the first embodiment of the present invention. 2 is a schematic diagram showing irradiation of an ultrasonic wave to a test eye 12. FIG. 1 is an explanatory diagram showing the effect of ultrasonic irradiation on retinal blood vessels of a subject's eye 12. FIG. 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. 5 is a flowchart showing a process of calculating elasticity of a blood vessel in step 512 of FIG. 4. This is a schematic diagram showing a state in which a vein is curved like an arch because an artery that has expanded to the peripheral side due to arteriosclerosis pulls the vein through the vascular wall. 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. This is a schematic diagram showing a condition in which the vascular wall of an arteriosclerotic artery hides the blood flow in the vein, making the tip of the vein at the crossing appear narrower. This is a schematic diagram showing how arterial walls thickened by arteriosclerosis impede blood flow in veins. 1 is a schematic diagram showing a display image displayed on a display of a viewer 150. FIG. FIG. 11 is a block diagram showing a configuration of an ophthalmic apparatus 210 according to a second embodiment of the present invention.

[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 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 a fundus image. The server 140 stores a plurality of fundus images obtained by photographing the fundus of a plurality of patients by the ophthalmologic apparatus 110 in association with the patient ID. The viewer 150 displays the fundus images acquired by the server 140 and analysis results.

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

The server 140 stores images of the subject's eye captured by the ophthalmic device 110 in correspondence with the patient's ID. The viewer 150 displays data acquired by the server 140 (images of the subject's eye, analysis results to assist diagnosis, etc.).

The ophthalmic device 110, the server 140, and the viewer 150 are connected to each other via the network 130. The viewer 150 is a client in a client-server system, and multiple viewers 150 are connected via the network. In addition, multiple servers 140 may also be connected via the network to ensure system redundancy. Alternatively, if the ophthalmic device 110 has an image processing function and the image viewing function of the viewer 150, fundus images can be acquired, processed, and viewed in a standalone state of the ophthalmic device 110. If the server 140 has the image viewing function of the viewer 150, fundus images can be acquired, processed, and viewed in a configuration of the ophthalmic device 110 and the server 140.

In addition, other ophthalmic devices (examination devices for visual field measurement, intraocular pressure measurement, etc.) 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.

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 the "X direction", the vertical direction relative to the horizontal plane is 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 the "Z direction". Therefore, the X direction, Y direction, and Z direction are perpendicular to each other.

The ophthalmic device 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 the 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 disclosed herein.

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

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.

The control device 116 also includes an image processing device 17 connected to the 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 performs various image processing operations in cooperation with the CPU 16A. The control device 116 is connected to the network 130 via the communication interface 16F.

As described above, in FIG. 2, the control device 116 of the ophthalmic device 110 is provided with an 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 device 110 may not be provided with the input/display device 16E, but may instead be provided with a separate input/display device that is physically independent of the ophthalmic device 110.

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.

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 capable of deflecting a light beam, such as a polygon mirror or a galvanometer mirror. It may also be a combination of these.

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 optical system combining concave mirrors and lenses. 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 in the center of the fundus but also in the peripheral part of the fundus.

When using a system including an elliptical mirror, 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.

The wide-angle optical system 30 realizes observation of the fundus with a wide field of view (FOV) 12A. The FOV 12A indicates the range that can be photographed by the photographing 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 irradiation angle and an external irradiation angle. The external irradiation angle is the irradiation angle of the light beam irradiated from the ophthalmic device 110 to the subject's eye 12, which is defined based on the pupil 27. The internal irradiation angle is the irradiation angle of the light beam irradiated to the fundus, which is defined based on 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 approximately 160 degrees. In this embodiment, the internal irradiation angle is 200 degrees.

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 is an abbreviation for Ultra Wide Field. The wide-angle optical system 30, which has an ultra-wide fundus field of view (FOV), can capture an image of the area from the posterior pole of the fundus of the subject eye 12 beyond the equator, and structures present in the peripheral part of the fundus, such as retinal blood vessels, can be captured.

The SLO system is realized by the control device 116, the SLO unit 18, and the imaging optical system 19 shown in FIG. 2. The SLO system is equipped with a wide-angle optical system 30, which enables fundus imaging with a wide FOV 12A.

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 to one 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 to one optical path.

The SLO unit 18 is configured to be able to switch between a light source that emits laser light of different wavelengths or a combination of light sources that emit light, 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, four light sources are provided: a light source 40 of B light, a light source 42 of G light, a light source 44 of R light, and a light source 46 of IR light, but 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 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.

The light incident on the imaging 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.

The SLO unit 18 includes a beam splitter 64 that reflects B light and transmits light other than B light from the posterior segment (fundus) of the subject's eye 12, and a beam splitter 58 that reflects G light and transmits light other than 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 light other than 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 detection element 70 that detects B light reflected by the beam splitter 64, a G light detection element 72 that detects G light reflected by the beam splitter 58, an R light detection element 74 that detects R light reflected by the beam splitter 60, and an IR light detection element 76 that detects IR light reflected by the beam splitter 62.

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 incident light passes through the beam splitter 58 in the case of R light, is reflected by the beam splitter 60, and is received by the R light detection element 74. The incident light passes through the beam splitters 58 and 60 in the case of IR light, is reflected by the beam splitter 62, and is received by the IR light detection element 76. 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.

The control device 116 also controls the light sources 40, 42, 44 to emit light simultaneously. The fundus of the test eye 12 is photographed simultaneously with B light, G light, and R light, thereby obtaining a G-color fundus image, an R-color fundus image, and a B-color fundus image in which each position corresponds to each other. 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 the fundus of the test eye 12 is photographed simultaneously with G light and R light, thereby obtaining a G-color fundus image and an R-color fundus image in which each position corresponds to each other. An RG color fundus image is obtained from the G-color fundus image and the R-color fundus image.

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 eye 12 with measurement light all at once. The OCT unit 200 can acquire OCT data of structures present in the periphery 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.

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 linear polarization, lenses 164 and 166 that collimate the light beam and expand its beam diameter, a cube-type beam splitter 168 that splits the light beam into measurement light 192 and reference light 190 and generates interference light 194 by interfering between them, a wavelength plate 170 that polarizes the reference light 190, and a reflecting mirror 172 that totally reflects the reference light 190 with a reflecting surface perpendicular to the traveling direction of the reference light 190.

In the XYZ coordinate system shown in FIG. 2, the Z direction is the direction of travel of the light beam output from the light source 160, and the X-Y plane is defined as the vibration plane of the light beam perpendicular to the Z direction. The X and Y directions are defined 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 direction of travel 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.

The polarizing plate 162 is a polarizing element consisting of a linear polarizer for adjusting 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 passes through the polarizing plate 162 has a linear polarization 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 the S-polarized component of the light beam each have the same amplitude.

The cube beam splitter 168 acts to split the parallel linearly polarized light beam into measurement light 192 directed toward the test 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 test eye 12 via the objective lens 176.

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, generating interference light 194.

The wavelength plate 170 is a polarization conversion element that converts the polarization characteristics of the reference light 190 that has been linearly polarized by the polarizing plate 162. In this embodiment, a 1/8 wavelength plate is used as the wavelength plate 170. As a result, a phase difference of π/4 is given between the P-polarized component and the S-polarized component of the reference light 190 when it passes through the wavelength plate 170. The reference light 190 is given the phase difference when it travels from the cube beam splitter 168 toward the reflecting mirror 172 and when it is reflected by the reflecting mirror 172 and re-enters the cube beam splitter 168, resulting in a phase difference of π/2. Therefore, since it acts like a 1/4 wavelength plate on the reference light 190 that has a 45° linear polarization, the reference light 190 that re-enters the cube beam splitter 168 is converted into circularly polarized light.

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.

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 obtains an X-Y tomographic image of any depth region of the subject's eye 12 in a single capture, i.e., over the entire field of view.

The ophthalmic device 110 in this embodiment also includes an ultrasonic probe 120 that irradiates ultrasonic waves to the subject's eye. 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 press against the subject's eye, compressing the blood vessels of the subject's eye.

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

Figure 4 is a flowchart showing the retinal blood vessel elasticity measurement process in this embodiment. A case where the process shown in Figure 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 Figure 3, the program has an OCT data acquisition function, an image processing function, and a processing function. By the CPU 16A executing a program having each of these functions, the CPU 16A functions as the OCT data acquisition unit 204, the image processing unit 206, and the processing unit 208. Note that the image processing function includes the achievement of 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 includes a computer-readable storage medium that is not a temporary signal itself, the computer-readable storage medium stores the program, and the program causes a computer to execute the steps of acquiring a first tomographic image of the subject's eye with the ultrasound irradiation unit turned off, acquiring a second tomographic image of the subject's eye with the ultrasound irradiation unit irradiating the subject's eye with ultrasound, 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.

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

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 specified area of the fundus all at once. The specified 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 position of the specified area is centered on the optic disc. Alternatively, the position of a fixation target (not shown) may be changed to change the orientation of the test eye 12 relative to the optical axis, and the position of the specified area may be set to the periphery of the fundus.

In step 504, the OCT data acquisition unit 204 does not operate the ultrasound probe 120 (turns it OFF) and acquires the first OCT data for the set OCT scan position. The first OCT data is OCT data for a specified area in the absence of ultrasound irradiation. The processing unit 208 then stores and holds the acquired first OCT data in RAM 16B.

In step 506 , the OCT data acquisition unit 204 operates (turns ON) the ultrasonic probe 120 to irradiate the subject's eye 12 with ultrasonic waves.
5 is a schematic diagram showing ultrasonic irradiation to the subject's eye 12. The ultrasonic probe 120 irradiates focused ultrasonic waves having a frequency and output sufficient to contract retinal blood vessels toward the fundus of the subject's eye 12. 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.

Figure 6 is an explanatory diagram showing the effect of ultrasonic irradiation on the fundus of the test eye 12. As shown in Figure 6, ultrasonic irradiation of the fundus presses the vascular wall 302 of the retinal blood vessel, compressing the retinal blood vessel in the Z-axis direction. The elastic modulus of the retinal blood vessel can be measured from the first OCT data and the second OCT data.

Figure 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. The higher the Young's modulus, the more advanced the hardening of the blood vessel wall is. In addition, 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 indicating the elasticity of the retinal blood vessels is calculated based on OCT data when ultrasound is irradiated to the fundus of the test eye 12 and OCT data when ultrasound is not irradiated. In other words, in the OCT data when ultrasound is irradiated, the harder the blood vessel wall is (the higher the Young's modulus), the smaller the strain of the blood vessel wall is, and the softer the blood vessel wall is (the smaller the Young's modulus), the greater the strain of the blood vessel wall is. Therefore, by measuring the magnitude of strain from OCT data when ultrasound is irradiated to the fundus of the test eye 12 and OCT data when ultrasound is not irradiated, the Young's modulus of the blood vessel wall at the time of measurement can be calculated.

In step 508, the OCT data acquisition unit 204 acquires second OCT data at the set OCT scan position while ultrasonic waves are 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 ultrasonic waves are 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.

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.

Figure 8 is a flowchart showing the process of calculating the elastic modulus of blood vessels in step 512 of Figure 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 Figure 8 may be performed by a CPU provided in the server 140.

In step 902, the image processor 206 identifies the 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 the region where blood vessels exist using the first OCT data, or by extracting the 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, in the fundus, the intersection of retinal blood vessels is a site where vitreous hemorrhage or retinal detachment is likely to occur, so the region including the intersection of blood vessels may be preferentially identified as the first vascular region. In addition, in this embodiment, full field OCT is possible, in which OCT data of the fundus is acquired all at once by irradiating the fundus of the test eye 12 with measurement light all at once, so the entire fundus may be the first vascular region.

Figures 9A, 9B, 9C, and 9D are schematic diagrams showing examples of the arteriovenous crossing phenomenon. Figure 9A shows a state in which an artery 300A that has been extended to the peripheral side due to arteriosclerosis pulls a vein 300V through the vascular wall, causing the vein 300V to curve in an arch at the intersection with the artery 300A.

Figure 9B shows a state in which arteriosclerosis has progressed and the vascular wall has thickened, causing the vascular wall of artery 300A to conceal vein 300V at the crossing (because the measurement light is blocked by the vascular wall of artery 300A and does not reach vein 300V), making it appear as if blood flow in vein 300V has been cut off.

Also, as shown in Figure 9C, there are cases where the vascular wall of the artery 300A, which has advanced arteriosclerosis, hides the blood flow in the vein 300V, making the tip of the vein 300V at the crossing appear narrow.

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

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

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

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.

In step 908, the blood vessel size in the second blood vessel region is measured based on the second OCT data. The blood vessel size 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.

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).

E=σ/ε…(1)

In step 912, the data on the elastic modulus of the blood vessel 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 on the elastic modulus of the blood vessel may be data that combines the position of the pixel of the blood vessel and the elastic modulus at that position. Furthermore, the data may include pixel brightness, blood vessel diameter, etc.

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.

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 the information received from the server 140, the information display area 502 displays each piece of information in each display area from the patient ID display area 512 to the axial length display area 522.

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, 534 of blood vessels at the position indicated by the arrow 536 are displayed. The blood vessels displayed in the fundus image 530 are color-coded or otherwise changed in display form according to their elasticity. Generally, the elasticity of a healthy retina is about 10 kPa. The elasticity of retinal blood vessels has a certain range, 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 that the SLO image and the en-face image are registered and the blood vessel portion of the SLO image is color-coded using elasticity data.

Tomographic image 532 is a tomographic image of the blood vessel before ultrasound irradiation, and tomographic image 534 is a tomographic image during ultrasound irradiation.

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

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 ultrasound irradiation OFF, and the blood vessel diameter with ultrasound irradiation ON.

As described above, in this embodiment, focused ultrasound is irradiated onto the retina of the test 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.

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 possible lesions based on the elasticity of retinal blood vessels is required near the optic disc, macula, or at the arteriovenous intersection.

Blood vessel elasticity measurements are generally performed using an invasive method 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, which is one method of measuring elasticity, is easily affected by the movement of the living body, so high speed is required during measurement.

In this embodiment, full field OCT is used to acquire OCT data of a specific area of the fundus all at once, so that the elastic modulus can be measured and the elastic modulus of multiple blood vessels present in the specific area can be calculated. This is because when acquiring OCT data by two-dimensional scanning with laser light using a point sensor and a scanner, the state of the blood vessels may change during the two-dimensional scanning due to the influence of pulsation, beating, fixational eye movement, etc. In full field OCT, the first OCT data of the specific area is captured at the same time t1, and the first OCT data is not captured at different times depending on the location (the second OCT data is also captured at the same time t2). Therefore, full field OCT can perform elastic modulus measurement with higher accuracy than two-dimensional scanning.

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 (e.g., a blood vessel position specified by the user) may be calculated.

In this embodiment, strain imaging is performed non-invasively by externally irradiating the fundus of the test eye 12 with focused ultrasound, and full-field OCT technology is applied to enable high-speed imaging and reduce measurement errors caused by biological movement, which is a weakness of strain imaging.

In this embodiment, ultrasonic waves are not irradiated to the test eye 12 when the first OCT data is acquired, and ultrasonic waves are irradiated to the test eye 12 when the second OCT data is acquired, but this is not limited to the above. For example, ultrasonic waves may be irradiated to the test eye 12 at a first output when the first OCT data is acquired, and ultrasonic waves may be irradiated to the test 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 formula (1), the pressure (stress) σ that the ultrasonic probe 120 applies to the fundus of the test eye 12 is a value corresponding to the difference between the first output and the second output. Furthermore, with such a configuration, if ultrasonic waves are not irradiated to the test eye 12 when the first OCT data is acquired, the first output is set to 0.

In this embodiment, the processing shown in Figures 4 and 8 is performed by the ophthalmic device 110, but it may also be performed by the server 140 after the first OCT data and the second OCT data are acquired by the ophthalmic device 110. When performed by the server 140, steps 512 to 518 of the flowchart in Figure 4 are executed by the CPU of the server 140, and a display screen 500 that visualizes the elasticity 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. Thus, the user of the viewer 150 can view the display screen 500, and information that supports the diagnosis of the examined eye can be displayed.

The CPU of the server 140 executes an image processing program to visualize the elasticity of the retina. The CPU of the server 140 executes an image processing program corresponding to steps 512 to 518 of the flowchart in FIG. 4, so that 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 device 110.

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 an OCT unit that scans the subject's eye by point scanning is used, and the imaging optical system 119 includes an OCT scanner 24 for point scanning. However, other configurations are the same as those of the first embodiment, so the same components are given the same reference numerals and detailed descriptions are omitted. Point scanning is a scanning method in which a laser beam is irradiated to a point on the subject's eye, and the reflected light from the subject's eye is received by a point sensor. It is a scanning method in which a predetermined area of the subject's eye is imaged by scanning with a laser beam.

Figure 11 is a block diagram showing the configuration of an ophthalmic apparatus 210 according to this embodiment. As shown in Figure 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.

As in the first embodiment, the control device 16 includes a computer having a CPU 16A, RAM 16B, ROM 16C, and an 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 is omitted.

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

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.

The light emitted from the light source 20A is branched by the first optical coupler 20C. One of the branched lights is collimated by the collimating lens 20E as a measurement light, and then two-dimensionally scanned in the X and Y directions by the OCT scanner 24 and is 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 then incident on the second optical coupler 20F via the collimating lens 20E and the first optical coupler 20C. The OCT scanner 24 may be any optical element capable of deflecting a light beam, and may be, for example, a polygon mirror or a galvanometer mirror. It may also be a combination of these.

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 passes through the reference optical system 20D to be incident on the second optical coupler 20F.

The light beams incident on the second optical coupler 20F, i.e., the measurement light reflected by the fundus and the reference light, are interfered with by the second optical coupler 20F to generate interference light. The interference light 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.

Here, an OCT image obtained by capturing an image with an internal illumination angle of 160 degrees or more, or an OCT image obtained by scanning the peripheral area of the fundus, is referred to as a UWF-OCT image.

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 a storage device.

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, such as SD-OCT (Spectral-Domain OCT) and TD-OCT (Time-Domain OCT), may also be used.

In this embodiment, the elastic modulus of the retinal blood vessels is calculated basically by the process shown in Fig. 4 and Fig. 8. However, in this embodiment, OCT imaging is performed using point scanning to acquire OCT data locally, rather than full field OCT, which acquires fundus OCT data all at once by irradiating the fundus of the subject eye 12 with measurement light all at once, so 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.

In this embodiment, the first OCT data and the second OCT data are obtained by performing a tomographic image capture along the blood vessels in the retina. Therefore, the OCT scan position may be set by extracting the area where blood vessels are present from the OCT data obtained by separately performing an OCT scan of the entire fundus, or by extracting the area where blood vessels are present using SLO data in combination. Alternatively, the OCT scan position may be set by angiography (angiography) using a contrast agent. In addition, 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.

In step 902 of FIG. 8, a region including a vascular intersection as shown in FIG. 9A, FIG. 9B, FIG. 9C, and FIG. 9D may be preferentially identified as the first vascular region.

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

As described above, in this embodiment, by capturing cross-sectional images along blood vessels, the number of measurement points is reduced, enabling high-speed imaging and reducing measurement errors caused by biological movement, which is a weakness of strain imaging.

In addition, in this embodiment, the elasticity of the retinal blood vessels can be calculated by using a device capable of OCT imaging by a point scanning method using a point sensor that is less expensive than a device capable of full field OCT. In addition, in SD-OCT, the elasticity of the retinal blood vessels can be measured by changing the detector from a point sensor to one consisting of a spectrometer and a line sensor.

The image processing in each embodiment described above is merely an example. 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.

In each of the embodiments described above, 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). A portion of the image processing may be performed by a software configuration, and the remaining processing may be performed by a hardware configuration.

12 Subject's eye 14 Photography 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 Collimator lens 20F Optical coupler 22 Optical scanner 24 OCT scanner 100 Ophthalmic system 110 Ophthalmic device 116 Control device 119 Photography optical system 120 Ultrasonic probe 130 Network 140 Server 150 Viewer 160 Light source 168 Cube-type beam splitter 190 Reference light 192 Measurement light 194 Interference light 200 OCT unit 204 OCT data acquisition unit 206 Image processing unit 208 Processing unit 210 Ophthalmic device 300A Artery 300V Vein 302 Blood vessel wall

Claims (16)

an ultrasonic irradiation unit that applies ultrasonic waves to the subject's eye;
a tomographic image acquisition unit that acquires a set of tomographic images of the subject's eye by a two-dimensional detector;
a control unit that controls the ultrasonic irradiation unit and the tomographic image acquisition unit to acquire a first tomographic image of the test eye in a state where a first ultrasonic wave having a first output is irradiated to the test eye from the ultrasonic irradiation unit, and to acquire a second tomographic image of the test eye in a state where a second ultrasonic wave having a second output different from the first output is irradiated to the test eye from the ultrasonic irradiation unit;
an image processing unit that identifies a first vascular region from the first tomographic image and a second vascular region from the second tomographic image, and calculates an elastic modulus of the blood vessel of the subject's eye based on the first vascular region and the second vascular region ;
13. An ophthalmic device comprising: a blood vessel position identifying unit that identifies the positions of retinal blood vessels from a retinal image of the subject's eye;
an ultrasonic irradiation unit that applies ultrasonic waves to a specific location of the subject's eye;
A light source that emits broadband light;
a branching unit that branches the light emitted from the light source into a measurement light and a reference light that are to be irradiated onto the fundus of the subject's eye;
an interference unit that generates interference light between the reference light and reflected light generated by reflection of the measurement light on the fundus of the subject's eye;
a scanning unit that scans the retinal blood vessels whose positions are identified by the blood vessel position identifying 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 subject's eye based on the detection signal;
a control unit that controls each of the ultrasound irradiation unit, the light source, the interference unit, the scanning unit, the detection unit, and the image processing unit so as to obtain a first tomographic image of the test eye while irradiating the test eye with a first ultrasound wave of a first output from the ultrasound irradiation unit, and obtain a second tomographic image of the test eye while irradiating the test 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 test eye based on the first tomographic image and the second tomographic image;
13. An ophthalmic device comprising: 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.
An ophthalmic apparatus according to claim 2. The first output is 0, and the second output is an output sufficient to constrict blood vessels in the fundus.
The ophthalmic apparatus according to any one of claims 1 to 3. The ophthalmic device according to any one of claims 1 to 4, wherein the control unit calculates the elastic modulus of the blood vessel by dividing a first difference calculated from a first pressure when the first ultrasonic wave is applied and a second pressure when the second ultrasonic wave is applied by a second difference calculated 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 device according to any one of claims 1 to 5, wherein the blood vessels are retinal blood vessels. The ophthalmic device according to any one of claims 1 to 6, wherein the ultrasound is focused ultrasound. acquiring first tomographic images of the subject's eye collectively using a two-dimensional detector while irradiating the subject's eye with a first ultrasonic wave at a first output from an ultrasonic irradiation unit;
acquiring second tomographic images of the subject's eye collectively by the two-dimensional detector in a state in which second ultrasonic waves having a second output different from the first output are irradiated to the subject's eye from the ultrasonic irradiation unit;
specifying a first vascular region from the first tomographic image and a second vascular region from the second tomographic image, and calculating an elastic modulus of a blood vessel of the subject's eye based on the first vascular region and the second vascular region;
An image processing method comprising: Identifying a position of a retinal blood vessel from a retinal image of the test eye;
Irradiating a retinal blood vessel position of the subject's eye with a measurement light obtained by splitting a reference light from a broadband light emitted from a light source and a first ultrasonic wave having a first output from an ultrasonic irradiation unit;
generating interference light between the reference light and a reflected light generated by reflection of the measurement light irradiated to the subject's eye;
detecting the interference light and outputting a first tomographic image of the subject's eye;
Irradiating the measurement light and a second ultrasonic wave having a second output different from the first output from the ultrasonic irradiation unit to the retinal blood vessel position of the subject's eye, respectively;
generating interference light between reflected light generated by reflection of the measurement light from the subject's eye and the reference light;
detecting the interference light and outputting a second tomographic image of the subject's eye;
Calculating elasticity of blood vessels of the subject's eye based on the first tomographic image and the second tomographic image;
An image processing method comprising: The image processing method according to claim 8 or 9, wherein the first output is 0, and the second output is an output sufficient to constrict blood vessels in the subject's eye. The image processing method according to any one of claims 8 to 10, wherein the elastic modulus of the blood vessels in the fundus of the subject eye is calculated by dividing a first difference between a first pressure due to the first ultrasonic wave and a second pressure due to 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 11, wherein the blood vessels are retinal blood vessels. The image processing method according to any one of claims 8 to 12, characterized in that each of the first ultrasonic wave and the second ultrasonic wave is a focused ultrasonic wave. an ultrasonic irradiation unit that applies ultrasonic waves to the subject's eye;
a tomographic image acquisition unit that acquires a set of tomographic images of the subject's eye by a two-dimensional detector;
a control unit that controls the ultrasonic irradiation unit and the tomographic image acquisition unit to acquire a first tomographic image of the test eye in a state where the ultrasonic irradiation unit is turned off, and to acquire a second tomographic image of the test eye in a state where the ultrasonic irradiation unit is irradiated with ultrasonic waves;
an image processing unit that identifies a first vascular region from the first tomographic image and a second vascular region from the second tomographic image , and calculates an elastic modulus of the blood vessel of the subject's eye based on the first vascular region and the second vascular region ;
13. An ophthalmic device comprising: a blood vessel position identifying unit that identifies the positions of retinal blood vessels from a retinal image of the subject's eye;
an ultrasonic irradiation unit that applies ultrasonic waves to a specific location of the subject's eye;
A light source that emits broadband light;
a branching unit that branches the light emitted from the light source into a measurement light and a reference light that are to be irradiated onto the fundus of the subject's eye;
an interference unit that generates interference light between the reference light and reflected light generated by reflection of the measurement light on the fundus of the subject's eye;
a scanning unit that scans the retinal blood vessels whose positions are identified by the blood vessel position identifying 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 subject's eye based on the detection signal;
a control unit that controls the ultrasound irradiation unit to obtain a first tomographic image of the subject's eye while the ultrasound irradiation unit is turned off, and to obtain a second tomographic image of the subject's eye while the ultrasound irradiation unit is irradiating the subject's eye with ultrasound, and calculates elasticity of blood vessels of the subject's eye based on the first tomographic image and the second tomographic image;
13. An ophthalmic device comprising: the blood vessel is a blood vessel in the fundus of the eye,
The ophthalmologic apparatus according to claim 14 or 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 elasticity modulus.