Ophthalmological image processing device, ophthalmological image processing program

Abstract

To solve the problem that it is difficult to select a plurality of sets of OCT data different in time interval, to generate motion contrast data in the respective sets, and to selectively identify blood stream slow in blood flow rate in an added image to which the created motion contrast data is added.SOLUTION: An ophthalmologic image processing device has: OCT data acquisition means which acquires three or more OCT data temporarily different with respect to an identical position of the eye to be tested; and OCT motion contrast image generation means which generates a plurality of OCT motion contrast images having different blood flow drawing ranges from a set of OCT data having a different temporal interval of the acquired OCT data. The ophthalmologic image processing device has image generation means which generates difference images expressing differences in the plurality of OCT motion contrast images having the different blood flow drawing ranges identifiably.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The disclosure of this specification relates to an ophthalmic image processing device and an ophthalmic image processing program. [Background technology]

[0002] OCT (Optical Coherence Tomography) is known as a device for observing a subject's eye. This device can be used to perform follow-up observation by comparing images of the same subject's eye taken at different times and dates, and data generated and analyzed from the images, over time. In addition, vascular information of the subject's eye can be obtained by generating motion contrast data based on OCT data obtained by taking multiple images of the same position of the same subject's eye. In this case, as a method for obtaining a large amount of vascular information with a small number of images, Patent Document 1 discloses a configuration of an OCT signal processing device that selects multiple sets of OCT data with different time intervals, generates motion contrast data for each set, and adds and displays the created motion contrast data. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO2017 / 119437 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in Patent Document 1, an additive image of motion contrast data including both slow and fast blood flow velocities is generated, making it difficult to selectively depict blood flow with a relatively slow blood flow velocity. [Means for solving the problem]

[0005] A first embodiment of the present invention is an ophthalmologic image processing device having an OCT data acquisition means for acquiring three or more temporally different OCT data for the same position of a subject's eye, and an OCT motion contrast image generation means for generating an OCT motion contrast image having different blood flow rendering ranges from a set of OCT data having different time intervals among the acquired OCT data, The ophthalmologic image processing device has an image generating means for generating a difference image that represents a difference between at least two of the multiple OCT motion contrast images having different blood flow rendering ranges in a distinguishable manner.

[0006] A second embodiment of the present invention is an OCT data acquisition means for acquiring three or more OCT data pieces at different times for the same position of a subject's eye; an OCT motion contrast image generating means for generating OCT motion contrast images having different blood flow rendering ranges from sets of OCT data having different time intervals among the acquired OCT data; An ophthalmological image processing program comprising: The ophthalmologic image processing device has a composite image generation means for generating a composite image by assigning any of different RGB channels to each of at least two of the multiple OCT motion contrast images having different blood flow drawing ranges.

[0007] A third embodiment of the present invention includes an OCT data acquisition step of acquiring three or more OCT data pieces at different times for the same position of a subject's eye; an OCT motion contrast image generating step of generating OCT motion contrast images having different blood flow rendering ranges from sets of OCT data having different time intervals among the acquired OCT data; An ophthalmological image processing program comprising: The ophthalmologic image processing program includes an image generation step of generating a difference image that identifiably expresses the difference between at least two of the multiple OCT motion contrast images having different blood flow drawing ranges. Effect of the Invention

[0008] It is possible to provide an ophthalmologic image processing device and an ophthalmologic image processing program capable of depicting a blood flow with a relatively slow blood flow velocity. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a diagram illustrating an example of a process performed by the image processing device according to the first embodiment. [Diagram 2] FIG. 1 illustrates an example of a configuration of an image processing system according to a first embodiment. [Diagram 3] FIG. 2 is a diagram illustrating an example of a processing flow of the image processing device according to the first embodiment. [Figure 4] FIG. 13 is a diagram showing an example of a report screen according to the first embodiment. [Diagram 5] FIG. 13 is a diagram showing an example of a report screen according to the first embodiment. [Figure 6] FIG. 4 is a diagram showing an example of a method for acquiring OCT data according to the first embodiment. [Figure 7] FIG. 11 is a diagram illustrating an example of a processing flow of the image processing device according to the second embodiment. [Figure 8] FIG. 11 is a diagram showing an example of a report screen according to the second embodiment. [Figure 9] FIG. 13 is a diagram showing an example of a method for displaying an analysis result according to the third embodiment. [Figure 10] FIG. 13 is a diagram showing an example of a report screen according to the fourth embodiment. [Figure 11] FIG. 13 is a diagram showing an example of a report screen according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments will be described with reference to the drawings. The same or equivalent components, members, and processes shown in each drawing will be given the same reference numerals, and duplicated descriptions will be omitted as appropriate. In addition, some components, members, and processes that are not important for the explanation may be omitted in each drawing. EXAMPLES

[0011] <Example 1> 2 is a diagram showing an example of the configuration of an ophthalmic examination system according to Example 1. The ophthalmic examination system according to Example 1 includes an OCT imaging device 201, an ophthalmic image processing device 209 (hereinafter, may be referred to as an image processing device 209), and a display unit 210. Moreover, the ophthalmic image processing device 209 of this embodiment performs each step according to an ophthalmic image processing program.

[0012] The OCT imaging device 201 acquires a signal indicating a tomographic image of the subject's eye based on a two-dimensional measurement range and measurement depth information specified for, for example, the fundus surface of the subject's eye. The OCT imaging device 201 is, for example, a Spectral-Domain OCT (SD-OCT). As shown in FIG. 2(a), the OCT imaging device 201 includes a light source 202, a half mirror 203, a galvanometer mirror 204, an objective lens 205, a reference mirror 206, a diffraction grating 207, and a line sensor 208.

[0013] The low-coherence light emitted from the light source 202 is split into a measurement light and a reference light by the half mirror 203. The measurement light is incident on the subject's eye E via the galvanometer mirror 204 and the objective lens 205. The scanning position of the subject's eye can be changed by moving the galvanometer mirror 204. The signal light incident on the subject's eye is reflected and scattered by the subject's eye, and then returns to the half mirror 203 along the reverse optical path. The reference light is reflected and scattered by the reference mirror 206, and then returns to the half mirror 203 along the reverse optical path. The half mirror 203 generates interference light by superimposing the return light of the signal light and the reference light. The diffraction grating 207 separates the interference light into wavelength components of wavelengths λ1 to λn. The line sensor 208 detects the separated interference light for each wavelength component. The line sensor 208 outputs a signal according to the detection result.

[0014] More specifically, the image processing device 209 is, for example, a personal computer, and an internal CPU (not shown) reads a program stored in a storage unit 211 such as a hard disk and operates as an image processing unit, and also realizes functions such as processing image data taken from the storage unit 211 and generating a screen to be displayed by the display unit 210, and also controls the OCT imaging device 201. The display unit 210 is, for example, an LCD display connected to the personal computer, and displays various information, and functions as a user interface that accepts operation instructions from an operator together with an operation unit 212, which is a keyboard and a mouse also connected to the personal computer. In this embodiment, the image processing device 209 and the OCT imaging device 201 work together to function as one ophthalmic examination system, and generate an ophthalmic image diagnosis report (hereinafter, a report) that is composed of an image of the subject's eye captured by the OCT imaging device 201, an image analysis result, and the like. The processing device is not limited to a CPU, and may be a GPU or the like. In addition, although the above has been described as a configuration in which the display unit 210 and the operation unit 212 are separate, they may be integrated into one device, such as a touch panel, or may be a tablet terminal in which the image processing device 209, display unit 210, and operation unit 212 are integrated.

[0015] FIG. 2B is a diagram showing a list of the main functions of the image processing device 209.

[0016] Based on an operation instruction using the operation unit 212, the operator can set imaging conditions such as a scan pattern and an imaging range in the OCT imaging device 201.

[0017] The OCT imaging device control means 220 controls the OCT imaging device 201 based on the set imaging conditions to perform imaging. The OCT data acquisition means 213 acquires an output signal from the line sensor 208, or acquires OCT data stored in the storage unit 211.

[0018] The image processing device 209 generates, for example, a tomographic image of the fundus of the subject's eye by using Fourier transform based on the acquired OCT data. Note that a method for generating a tomographic image can be realized by a known method, and therefore a detailed description will be omitted. Note that the generated tomographic image may be stored in the storage unit 211, or may be stored in another device by data communication via a network.

[0019] The three-dimensional OCT image generating means 214 can construct a three-dimensional OCT image by processing the OCT data of the subject's eye acquired by the OCT data acquiring means and arranging it in an xyz coordinate system. For example, when generating a three-dimensional OCT image of the subject's eye, B-scan images acquired at multiple positions of the subject's eye can be arranged in an xyz coordinate system to construct a three-dimensional OCT image of the subject's eye. In this case, the direction of the B-scan may be a radial scan in which a specific part is scanned radially, or a raster scan in which a certain direction (horizontal or vertical) is scanned. In this specification, the irradiation of an arbitrary point of the subject's eye with measurement light is called an A-scan, and a tomographic image generated by the A-scan is called an A-scan image. Furthermore, the intermittent irradiation of the subject's eye with signal light along an arbitrary line is called a B-scan, and a tomographic image acquired by the B-scan is called a B-scan image.

[0020] The OCT motion contrast image generating means 217 generates motion contrast data by processing a plurality of OCT data at different times for the same position, which are acquired by the OCT data acquiring means 213. Then, a three-dimensional OCT motion contrast image can be constructed by arranging the generated motion contrast data in an xyz coordinate system.

[0021] The En-Face image generating means 219 generates an En-Face image (hereinafter, also referred to as a projected image), which is a two-dimensional image projected onto a plane based on two arbitrary reference planes in the depth direction (Z direction) from a three-dimensional image such as a three-dimensional OCT image or a three-dimensional OCT motion contrast image. Note that the En-Face image can be generated using various known methods, so detailed explanations will be omitted.

[0022] The OCT data selection means 215 can select OCT data to be used for generating OCT motion contrast data. The selection operation may be based on an instruction from the operation unit 212, or may be configured to select according to the imaging conditions.

[0023] The OCT motion contrast difference image generating means 218 generates a difference image that identifiably represents the difference between at least two of a plurality of OCT motion contrast images having different blood flow drawing ranges from sets of OCT data having different time intervals.

[0024] The report generating means 216 can display the generated images and analysis results as a report on the display unit 210, or output them to a printing device (not shown).

[0025] Next, the operation of the ophthalmologic image processing apparatus according to the first embodiment will be described with reference to FIGS.

[0026] 3, the OCT data acquisition means 213 acquires OCT data for generating at least three OCT images acquired at different times with a time interval of Δt for the same position. In this embodiment, as shown in FIG. 1(a), four OCT data are acquired from O1 to O4 for the same position with a time interval of Δt.

[0027] In step S302, the OCT data selection means 215 selects two or more sets of OCT data with different time intervals from the four acquired OCT data. In this embodiment, sets of OCT data with time intervals of Δt, 2Δt, and 3Δt are selected. At this time, three sets of OCT data (O1 and O2, O2 and O3, O3 and O4) can be selected as combinations of Δt, two sets (O1 and O3, O2 and O4) as combinations of 2Δt, and one set (O1 and O4) as combinations of 3Δt. Note that the configuration may be such that the operator uses the operation unit 212 to select the OCT data to be used for generating the motion contrast data.

[0028] In step S303, the OCT motion contrast image generating means 217 generates a three-dimensional OCT motion contrast image. In this embodiment, as shown in FIG. 1(b), OCT motion contrast images MC1 to MC3 are generated for each set of OCT data selected by the OCT data selecting means 215. A three-dimensional OCT motion contrast image is generated by performing the same process on OCT data at multiple positions. When generating one OCT motion contrast image from multiple sets of OCT data at the same time interval, the OCT motion contrast image can be generated using the statistics of the OCT motion contrast data generated in each data set. At this time, it is desirable to use the OCT motion contrast data generated from each set after positioning them. For example, a motion contrast image is generated from each set of three sets of OCT data acquired at a time interval of Δt, and the generated motion contrast images are averaged to generate MC1. Alternatively, statistics such as the maximum value, minimum value, and median value of the motion contrast data generated from each set may be used. Alternatively, the image quality of the generated motion contrast images may be evaluated, and the one with the highest evaluation value may be used. Note that noise removal processing or the like may be performed as appropriate.

[0029] In step S304, the En-Face image generating means 219 generates OCT front motion contrast images ME1 to ME3, which are En-Face images, from the three-dimensional OCT motion contrast image. Here, the OCT front motion contrast images generated from the sets of OCT data with time intervals of Δt, 2Δt, and 3Δt are respectively designated ME1, ME2, and ME3. In this embodiment, the En-Face image is generated under the conditions that the reference plane in the depth direction range is the nerve fiber layer and the ganglion cell layer, the representative value at the time of generating the En-Face image is the maximum value between the reference planes, and no artifact removal is performed. Note that the generation conditions of the En-Face image are not limited to this. For example, it may be configured to be set based on the shooting conditions, or it may be configured to allow the operator to set the reference plane.

[0030] In step S305, the OCT motion contrast difference image generating means 218 generates a difference image that identifiably expresses the difference between at least two images among a plurality of OCT motion contrast images having different blood flow rendering ranges generated from each of the sets of OCT data having different time intervals. The "blood flow rendering range" described here indicates the range of blood flow velocity rendered by the time interval of the set of OCT data used to generate the OCT motion contrast data. In this embodiment, ME1 is used as a reference image when generating a difference image, and MS1, which is a difference image between ME1 and ME2, and MS2, which is a difference image between ME1 and ME3, are generated. At this time, it is desirable to generate difference images after positioning ME1 to ME3. Alternatively, the OCT imaging device 201 may be configured to be able to follow the movement of the subject's eye when acquiring OCT data. This makes it possible to acquire OCT data of the same position of the subject's eye even if the subject's eye moves due to fixational micromovement or the like during acquisition of OCT data. As a result, positioning of ME1 to ME3 is not required in this step. When generating a difference image, each En-Face image may be subtracted from the reference image ME1, or the reference image may be subtracted from each En-Face image. Alternatively, MS2 may be generated as a difference image between ME2 and ME3. Regions with relatively high blood flow velocity can be depicted with a motion contrast image generated from a set of OCT data with a short time interval. On the other hand, in order to depict regions with relatively low blood flow velocity in a motion contrast image, it is necessary to use a set of OCT data with a long time interval. This is because the motion contrast image is generated based on the amount of change between OCT data, and regions with relatively low blood flow velocity have a small amount of change over time.

[0031] Therefore, since a motion contrast image generated from a set of OCT data with a long time interval and an OCT motion contrast image generated from a set of OCT data with a short time interval each depict blood flow according to the blood flow velocity, by generating a difference image that clearly depicts the difference between at least two of multiple OCT motion contrast images with different blood flow depiction ranges generated from sets of OCT data with different time intervals, it is possible to selectively depict blood flow with a relatively slow blood flow velocity, which would be difficult to distinguish using only ME1 to ME3, which are En-Face images generated by simply changing the time interval of a set of OCT data, or images generated by adding ME1 to ME3 together.

[0032] In this embodiment, a difference image is generated by calculating the difference in pixel values ​​of OCT motion contrast images having different blood flow rendering ranges as a difference image that identifiably expresses the difference between at least two images among a plurality of OCT motion contrast images having different blood flow rendering ranges generated from a set of OCT data having different time intervals, but the image is not limited to this as long as it identifiably expresses the difference. For example, one image among at least two images among a plurality of OCT motion contrast images having different blood flow rendering ranges may be set as a reference image, and the pixel values ​​of the other images may be divided by the pixel values ​​of the reference image. More specifically, it is an image in which each pixel value of each En-Face image (ME1 to ME3) is divided by the pixel value of the corresponding pixel of the reference image. Alternatively, a deviation from the reference image may be calculated. This makes it possible to calculate the rate of change from the reference image (in other words, a comparison value with the reference image). In addition, when generating a difference image by calculating the difference in pixel values, for example, an image obtained by binarizing the difference image using a threshold value or an image obtained by reducing minute change information by noise processing may be used. This makes it easier to distinguish a part with a large change.

[0033] In step S306, the difference image generated in step S305 and the reference image are synthesized to generate a synthetic image that is a different type of difference image from the difference image generated in step S305, which expresses the difference between at least two images among a plurality of OCT motion contrast images having different blood flow rendering ranges in a distinguishable manner. In this embodiment, a synthetic image MA is generated by synthesizing the difference images MS1 and MS2 generated in step S305 with the OCT front motion contrast reference image ME1. Here, the difference images MS1 and MS2 can also be called the first difference image and the second difference image. At this time, different color information can be assigned to each of the difference images MS1 and MS2 and synthesized. For example, red is assigned to MS1 and blue is assigned to MS2, and one of the RGB channels is assigned to each of MS1 and MS2 so that they have different color information. At this time, color information may not be assigned to the reference image ME1, and different RGB channels may be assigned to each of MS1 and MS2, or different RGB channels may be assigned to each of the reference images ME1, MS1, and MS2. Alternatively, colors having the same hue but different brightness or saturation may be assigned and synthesized.

[0034] This makes it possible to distinguish the blood flow of the blood flow velocity displayed in MS1 ​​and MS2 by color information in the composite image MA while checking the overall blood flow state by the information in the reference image ME1. Note that, in this embodiment, the difference images MS1 and MS2 are composited with the reference image ME1, but it is not limited to this as long as an image is generated that can distinguishably express the differences between multiple OCT motion contrast images having different blood flow rendering ranges.

[0035] Furthermore, a region with a large difference in the difference image may be displayed in a distinguishable manner. For example, a region in which pixels with a brightness equal to or greater than a threshold value are consecutively identified from the difference image MS2 for a certain period or more. The identified region may be displayed on the display image in a distinguishable manner, for example, by a marker 415. The display image may be any of MS1, MS2, the composite image MA, and the En-Face image (ME1 to ME3). Also, an OCT tomographic image including at least a part of the region with a large difference may be displayed. For example, the display control means calculates the center of gravity of the identified region, displays the OCT tomographic image acquired at a position passing through the calculated point (center of gravity) in the region 402, and displays the indices 430 and 431 at the corresponding positions (OCT tomographic image acquisition positions). This allows the operator to confirm the position of the region with a particularly large difference together with the difference information on the fundus surface and information in the depth direction. Note that the center of gravity of the extracted region is used in this embodiment, but is not limited thereto. For example, it may be the center of the region, the inner center, the outer center, or any other arbitrary point.

[0036] In step S307, a report including the composite image MA is displayed.

[0037] An example of the report display is shown in FIG. 4. In this embodiment, a fundus image captured by a fundus camera or SLO (SLO: Scanning Laser Ophthalmoscope) is displayed in the display area 401, and indices 430 and 431 indicating the acquisition positions of OCT data are superimposed on the fundus image. When the operator moves the indices 430 and 431 indicating the acquisition positions of OCT data by operating the operation unit 212, the display control means displays the OCT tomographic image of the corresponding acquisition position in the display area 402, and the operator can check the OCT tomographic image at the positions of the indices 430 and 431. In addition, the display control means displays the composite image MA generated in step S306 in the display area 411. At this time, the same indices (indices indicating the acquisition positions of the B-scan image displayed in the display area 402) are displayed at positions on the composite image MA corresponding to the positions of the indices 430 and 431 on the fundus image displayed in the display area 401. A color map indicating the correspondence between the color information of the composite image MA and the time interval of the OCT data is displayed in the area 412.

[0038] The operation unit 410 is an operation area where the composite image MA and the difference image can be switched, and the operator can operate the operation unit 410 to select which image, the composite image MA or the difference image, to display. The display control means updates the display in the display area 411 based on the operator's selection of the image to be displayed. In this embodiment, the operation unit 410 is operated to select the composite image MA or the difference image for the image to be displayed in the display area 411 (hereinafter, the display image), but the present invention is not limited to this. For example, as shown in FIG. 5, the OCT front motion contrast images ME1 to ME3 generated from each of the sets of OCT data with different time intervals may be selected. In this case, the motion contrast image generated from the set of OCT data at the desired position and the desired time interval may be displayed in the display area 402. For example, when the operator performs an operation to select the time interval 2Δt to display ME2 using the operation unit 410, the display control means of this embodiment displays the OCT motion contrast image based on the OCT data acquired at the positions of the indicators 430 and 431 with the time interval of 2Δt in the display area 402. This allows the user to check the OCT motion contrast tomographic image including information in the depth direction while checking a plurality of OCT motion contrast images (a plurality of OCT motion contrast images having different blood flow rendering ranges) generated from each set of OCT data with different time intervals. The configuration may be such that the difference image is selected in the operation unit 410 and the difference image can be switched and displayed in the display area 402. Although the present embodiment is configured to select the display image using the operation unit 410, this is not limiting. For example, the display image may be selected using the wheel of a mouse. This allows the operator to switch and display a plurality of OCT motion contrast images having different blood flow rendering ranges in a simple manner.

[0039] In this embodiment, both the difference image generated in step S305 and the composite image generated in step S306 by combining the reference image and the difference image are types of difference images, and are difference images that identifiably represent the differences between multiple OCT motion contrast images having different blood flow drawing ranges. Therefore, step S307 does not exist, and the difference image generated in step S306 may be displayed in the display area 411 as a difference image that identifiably represents the differences between multiple OCT motion contrast images having different blood flow drawing ranges.

[0040] In this embodiment, the combination for generating motion contrast data is selected from the acquired OCT data, but the OCT data may be acquired in consideration of the combination for generating motion contrast data. For example, the imaging sequence may be determined based on the time interval of an arbitrary set of OCT data specified by the operator via the operation unit 212, and imaging may be performed. Alternatively, the time intervals that can be specified may be presented in advance, and the operator may select one.

[0041] A B-scan image is acquired by performing A-scans of the subject's eye multiple times along an arbitrary line. The number of A-scans is an arbitrary number, and may be uniquely determined based on the shooting conditions, or the operator may set an arbitrary number. In this embodiment, the number of A-scans is 1024. When acquiring multiple B-scan images, the galvanometer mirror 204 is controlled to move back and forth as shown in FIG. 6(a). This is also the case when acquiring B-scan images at multiple positions of the subject's eye. The black circles in the figure indicate A-scan processing, the solid lines indicate processing for controlling the galvanometer mirror 204 to acquire B-scan images, and the dashed lines indicate processing for controlling the galvanometer mirror 204 without acquiring B-scan images. Since B-scan images cannot be acquired during the processing of the dashed lines in the figure, the time interval that the operator can specify may be limited. This processing time can be calculated in the OCT processing device 201 based on conditions such as the number of A-scans in one B-scan (1024 in this embodiment), the timing of acquiring the B-scan images, and the driving speed of the galvanometer mirror 204. For example, when acquiring a B-scan image as shown in Fig. 6(b), the time interval that can be specified is different from that in Fig. 6(a). For this reason, it is useful to present the time interval that the operator can specify in advance. Alternatively, the imaging conditions such as the number of A-scans and the imaging range may be set so that OCT data is acquired at the time interval specified by the operator.

[0042] In the present embodiment, when the OCT photographing device control means 220 is instructed by the operator to acquire OCT data at time intervals of 5 ms and 11 ms, for example, the OCT photographing device control means 220 controls the OCT data acquisition means 213 to acquire OCT data only at 0 ms, 5 ms, 10 ms, 11 ms, and 15 ms. In this case, if there is sufficient time until the next B-scan image is acquired after one B-scan image is acquired, a B-scan image at a different position of the subject's eye may be acquired, or the device may be configured to wait until the next B-scan image is acquired. Alternatively, the time interval may be set to be synchronized with the pulsation. This makes it possible to acquire only OCT data required to generate a desired difference image. In this embodiment, the fundus of the subject's eye is photographed, but the present embodiment is not limited to this. For example, the device may be configured to perform similar processing using OCT data acquired by photographing the anterior eye.

[0043] The above method enables an operator to easily compare multiple OCT motion contrast images having different blood flow rendering ranges based on differences in blood flow velocity.

[0044] [Variation 1] In this variant example 1, we describe an example in which a group of OCT frontal motion contrast images (or videos) having different blood flow drawing ranges generated from a set of OCT data having different time intervals generated in step S304 is used as another difference image that clearly represents the differences between multiple OCT motion contrast images having different blood flow drawing ranges.

[0045] The display control means 221 of this embodiment continuously displays a plurality of OCT front motion contrast images having different blood flow rendering ranges generated from the sets of OCT data having different time intervals generated in step S304 in order of the shortest time interval of each set of OCT data used for generation. Specifically, the display control means 221 continuously displays the aligned ME1 to ME3 in this order on the display unit 210. When continuously displayed, ME1 to ME3 may be displayed as a video with frames. By checking the continuously displayed plurality of OCT front motion contrast images having different blood flow rendering ranges, the operator can easily compare the OCT front motion contrast images taking blood flow velocity into consideration.

[0046] Alternatively, the display control means 221 of this embodiment may assign different color information (e.g., different RGB channels) to each of the multiple OCT motion contrast images (ME1 to ME3) having different blood flow rendering ranges from the set of OCT data having different time intervals generated in step S304, generate a composite image (generate a composite front motion contrast image), and display it on the display unit 210. For example, if there are two or three multiple OCT motion contrast images having different blood flow rendering ranges from the set of OCT data having different time intervals, an RGB channel may be assigned to each of the multiple OCT motion contrast images so that they have different color information, and generate a composite front motion contrast image. This makes it possible to distinguish blood flows with blood flow velocities that are difficult to distinguish only from the image generated by synthesizing ME1 to ME3 by color information while checking the overall blood flow information. By checking the composite OCT front motion contrast image, the operator can easily compare multiple OCT motion contrast images having different blood flow rendering ranges based on the difference in blood flow velocity by using color information.

[0047] <Example 2> In the first embodiment, a configuration for displaying the difference between at least two images among a plurality of OCT motion contrast images having different blood flow rendering ranges on an En-Face image was described. In this embodiment, a configuration for further displaying information in the depth direction will be described with reference to Figs. 7 and 8. Descriptions of the same configuration as in the first embodiment will be omitted.

[0048] Among the steps of this embodiment, steps S701 to S703 are similar to steps S301 to S303 of the first embodiment, respectively.

[0049] In step S705, the OCT motion contrast difference image generating means 218 sets one of the three-dimensional OCT motion contrast images generated from the aligned sets of OCT data having different time intervals as a three-dimensional OCT motion contrast reference image (sometimes referred to as a reference image), and generates a three-dimensional OCT motion contrast difference image which is the difference between the three-dimensional OCT motion contrast reference image and a three-dimensional OCT motion contrast image generated from a set of OCT data having a time interval different from the set of OCT data from which the three-dimensional OCT motion contrast reference image was generated. Since the OCT data has information in the depth direction, by calculating the difference between at least two images among a plurality of three-dimensional OCT motion contrast images having different blood flow rendering ranges generated from sets of OCT data having different time intervals, it becomes easier to grasp, for example, in which depth range a blood vessel region with a slow blood flow velocity is located.

[0050] In step S706, the three-dimensional OCT motion contrast difference image generated in step S705 and the three-dimensional OCT motion contrast reference image are combined to generate a three-dimensional OCT motion contrast combined image, which is a different type of difference image from the three-dimensional OCT motion contrast difference image generated in step S705.

[0051] In step S707, the display control means 221 displays a report including the three-dimensional OCT motion contrast composite image. In this embodiment, the three-dimensional OCT motion contrast composite image 414 is displayed in the display area 411. At this time, in order to show the positional relationship between the position on the fundus surface and the three-dimensional OCT motion contrast composite image 414, the display control means 221 displays a front image of the fundus separately captured by a fundus camera or SLO in the display area 413. The operator can operate the operation unit 212 to rotate, enlarge, reduce, and the like the three-dimensional OCT motion contrast composite image 414. In addition, the operator operates the operation unit 410, so that the display control means 221 can switch between displaying the three-dimensional OCT motion contrast composite image and the three-dimensional OCT motion contrast difference image generated in step S706. In this embodiment, both the three-dimensional OCT motion contrast difference image generated in step S705 and the three-dimensional OCT motion contrast composite image generated in step S706 by combining the three-dimensional OCT motion contrast reference image and the three-dimensional OCT motion contrast difference image are a type of difference image that identifiably represents the difference between multiple OCT motion contrast images having different blood flow drawing ranges, so step S707 does not exist, and the three-dimensional OCT motion contrast difference image generated in step S706 may be displayed in the display area 411 as a difference image that identifiably represents the difference between at least two of the multiple OCT motion contrast images having different blood flow drawing ranges.

[0052] Furthermore, the area with the largest difference is specified in the three-dimensional OCT motion contrast difference image, and an OCT tomographic image of an area including at least a part of the area is displayed in the display area 402 in the initial state, and the specified area P1 is displayed on the OCT tomographic image in a distinguishable manner. For example, as in the first embodiment, an area in which pixels with brightness equal to or greater than a threshold value are consecutively specified in the three-dimensional OCT motion contrast difference image, the center of gravity of the specified area is calculated, and the display control means 221 displays an OCT tomographic image including the calculated location (for example, a B-scan image acquired at a position passing through the calculated location) in the display area 402. At this time, the position on the OCT tomographic image corresponding to the specified area is displayed as P1. Alternatively, an area with pixels with brightness equal to or greater than a threshold value may be specified in an EnFace image generated based on a specific reference plane from the three-dimensional OCT motion contrast difference image, and displayed in the same manner. This makes it easier for the operator to confirm an area with a large difference in the depth range he or she is paying attention to. In this embodiment, the image displayed in the display area 402 is an OCT tomographic image, but a motion contrast image may be displayed. This makes it easier to check blood vessel regions with slow blood flow while checking the condition of the surrounding blood vessels.

[0053] Also, similarly to the first embodiment, the display control means 221 may display an En-Face image generated from a three-dimensional OCT motion contrast composite image or a three-dimensional OCT motion contrast difference image in the display area 411. For example, color information such as RGB channels according to depth information is assigned to the three-dimensional OCT motion contrast difference image generated in step S705, and an OCT front motion contrast difference image, which is an En-Face image, is generated by setting the reference plane as the upper end and lower end of the three-dimensional OCT motion contrast difference image. The operator can grasp the depth range in which the blood vessel region with a slow blood flow velocity is located by checking the color information of the OCT front motion contrast difference image displayed in the display area 411. Note that the configuration may be such that the operator can specify which depth information to assign color information to. As a result, for example, by adding color information only to the choroid layer, the region in the choroid layer with a slow blood flow velocity can be specified.

[0054] The above method allows the operator to easily check motion contrast data that takes into account blood flow velocity while grasping the position within the three-dimensional coordinate system.

[0055] <Example 3> In this embodiment, an image processing device having an analysis function related to OCT data will be described.

[0056] It is widely known that by analyzing OCT data and motion contrast data, it is possible to measure information related to blood vessels, such as the thickness of retinal layers such as the optic nerve fiber layer, the shape of the optic disc, blood vessel density, etc. Examples of blood vessel density include area density, which indicates the density of blood vessels per unit area, and skeleton density, which indicates the length of blood vessels per unit area.

[0057] One of the indicators of diabetic retinopathy is the analysis value calculated by the ETDRS (Early Treatment of Diabetic Retinopathy Study) grid. The ETDRS grid is an analysis chart consisting of nine sectors centered on the fovea, and the condition of the examined eye can be understood by analyzing the layer thickness and blood vessel density in each area (sector).

[0058] The display control means 221 of this embodiment superimposes and displays the analysis result on the composite image MA displayed on the display unit 210 in step S307 of embodiment 1. The image to be displayed may be the difference image MS1 or MS2 acquired in step S306.

[0059] For example, the operator can select, using a menu screen (not shown), whether or not to superimpose an ETDRS grid on the image displayed on the display unit 210. More specifically, for example, when the displayed image is a composite image MA and the operator selects to display an ETDRS grid on the composite image MA, the display control means 221 of this embodiment analyzes the analysis region set in the analysis target data related to the displayed image using the ETDRS grid on the composite image MA, as shown in Fig. 9(a), and displays the analysis results in each sector of the ETDRS grid.

[0060] The display control means 221 of this embodiment superimposes the ETDRS grid on the displayed composite image MA as an initial state when displaying the grid so that the center of the ETDRS grid coincides with the position of the fovea extracted by analyzing the fundus image such as OCT data or a separately acquired SLO image. In this embodiment, the center of the ETDRS grid is set to the fovea, but any part may be used as long as it is a part that is desired to be the center of the analysis target area. The operator can adjust the position and inclination of the analysis target area of ​​the composite image MA by moving the displayed ETDRS grid on the composite image MA. In this embodiment, the difference in blood vessel density obtained by analyzing the difference images MS1 and MS2 is displayed as a numerical value in each sector of the ETDRS grid on the composite image MA. This allows the operator to check which part has a relatively slow blood flow speed along with the numerical value while checking the surrounding blood vessel condition.

[0061] In this embodiment, the analysis target data is the difference images MS1 and MS2, but the analysis target data may be an image related to the display image, and is not limited to this. For example, the display image displayed in the display area 411 may be a composite image MA, and the analysis target data may be three-dimensional OCT data, with the analysis results of the OCT data, such as layer thickness, superimposed. This allows the operator to simultaneously check the analysis results regarding the layer thickness in addition to the blood vessel state and the state of change. Alternatively, the display image displayed in the display area 411 may be an En-Face image generated from the OCT data or a fundus front image acquired separately by a fundus camera or SLO, and the analysis target data may be a three-dimensional OCT motion contrast image in which the front image and position information are associated, with the analysis results of the motion contrast image, such as blood vessel density, superimposed. This allows the operator to simultaneously check the structure of the subject's eye and the change in the blood vessel state. In this embodiment, the analysis results are displayed using the ETDRS grid, but are not limited to this. For example, as shown in FIG. 9(b), the blood vessel density of each of the difference images MS1 and MS2 may be calculated, a color map to which color information according to the calculation result is assigned may be created, and the color map may be displayed on the composite image MA. Alternatively, instead of the ETDRS grid, a grid of any shape may be used, such as a perfect circle or ellipse whose interior is not divided, or a grid whose interior is divided into 3x3 blocks. This allows the operator to check the location where the change due to the time interval of the OCT data set is large while checking the blood vessel condition around the fovea. Note that the position where these grids are set is not limited to the fovea, and they can be set at any position, such as other parts of the image to be analyzed.

[0062] The above method allows the operator to easily confirm the analysis results regarding a difference image in which the difference between at least two images out of a plurality of OCT motion contrast images having different blood flow rendering ranges can be identified.

[0063] <Example 4> In this embodiment, a configuration is described that displays the change over time in a difference image that clearly represents the difference between at least two of multiple OCT motion contrast images having different blood flow rendering ranges generated from sets of OCT data at different time intervals using OCT data acquired at different dates and times.

[0064] The OCT data acquisition means 213 of this embodiment acquires multiple OCT data of the same subject eye acquired at different dates and times, performs the above-mentioned image processing on the OCT data at each date and time, and the display control means 221 can display it as a report, for example, as shown in Fig. 10(a). In this embodiment, when the operator selects one examination for which a report is to be displayed, the display control means 221 displays OCT motion contrast images based on OCT data acquired at four different dates and times, including the selected examination, for the same subject eye, in order of acquisition date and time. At this time, OCT motion contrast images generated from OCT data at different time intervals on the same examination date are displayed vertically.

[0065] If there are not four or more OCT data for the same examinee's eye, a message to that effect is displayed. The images of the four examinations displayed in the initial state are divided equally between the examination date and time of the oldest examination of the same examinee and the examination date and time selected by the operator, and the images of the examination with the examination date and time closest to the examination date and time are displayed. Alternatively, images of the four most recent examinations of the same examinee are displayed. Alternatively, images of any four examinations may be displayed. This allows the operator to simultaneously check changes in the OCT front motion contrast image over long time intervals, such as years, and changes over short time intervals, such as milliseconds.

[0066] Furthermore, the operator can select the type of image to be displayed using operation units 901 and 902. In this embodiment, a separately acquired SLO image, a projection image generated from OCT data, a difference image similar to MS1 to MS2 in the first embodiment, a composite image MA, and a continuous display image in the first modification can be selected using each operation unit.

[0067] For example, as shown in Fig. 10(b), by selecting a composite image MA and an SLO image as the type of image to be displayed, the operator can confirm the time-dependent change in structure on the SLO image while confirming the time-dependent change in a difference image that identifiably expresses the difference between at least two images among a plurality of OCT motion contrast images having different blood flow rendering ranges generated from sets of OCT data having different time intervals. Furthermore, an image that identifiably expresses the difference between the difference images or composite images MA similar to the MS1 to MS2 in the first embodiment, which are obtained at different dates and times, may be displayed.

[0068] Furthermore, the operator can operate the operation unit 903 to select and display images of examinations at different dates and times. Specifically, when the operator selects an examination for which the display is to be changed and then presses the operation unit 903, the display control means 221 of this embodiment displays an examination selection screen (not shown). The operator can update the images of the examination displayed in the report by selecting any examination displayed on the examination selection screen and closing the examination selection screen. The operator can use the operation unit 904 to externally save the displayed report in a file format or output it to a printer. Note that in this embodiment, four pieces of OCT data acquired at different dates and times are acquired and displayed as images, but this is not limited to this as long as there are multiple pieces of OCT data. For example, five pieces of OCT data acquired at different dates and times may be similarly displayed as images, or OCT data of the left and right eyes may be acquired on the same day and displayed as images. This makes it possible to easily check the time change of an OCT motion contrast image based on any multiple pieces of OCT data.

[0069] The above method allows the operator to easily confirm the change over time of a difference image that clearly represents the difference between at least two of multiple OCT motion contrast images having different blood flow drawing ranges.

[0070] [Variation 2] In this modified example, a configuration using an analysis function in addition to the fourth embodiment will be described. As shown in FIG. 11(a), the display control means 221 of this modified example displays OCT front motion contrast images with different acquisition dates and times and the results of analyzing layer thickness using an ETDRS grid, arranged vertically. The operator can adjust the position and inclination of the analysis target region by moving the displayed ETDRS grid on the composite image MA. When the operator moves the ETDRS grid on the OCT front motion contrast image of one of the examinations being displayed, the image processing device 209 of this embodiment can automatically move the ETDRS grid to the corresponding position on the OCT front motion contrast image of the other examination in conjunction with the ETDRS grid. Note that the image to be displayed may be not only the OCT front motion contrast image at a predetermined time interval, but also the composite image MA, the difference image MS1 or MS2, or any image as described above. As the analysis results, a graph in which the average retinal thickness of all the regions in the ETDRS grid is analyzed against the OCT data at each date and time is displayed in area 1001, and the results of analyzing the minimum retinal thickness in the smallest circle of the ETDRS grid, the average retinal thickness of all the regions in the ETDRS grid, and the retinal volume against the OCT data at each date and time are displayed in area 1002. In the graph in area 1001, the analysis results of the examination at the date and time selected by the operator are displayed in a distinguishable manner, and a regression line calculated from the analysis results plotted on the graph can be displayed. Note that, although the configuration is such that the retinal thickness of all the regions in the ETDRS grid is analyzed in this embodiment, the present invention is not limited to this. By operating the operation unit 1003, the operator can change the type of analysis results to be displayed to the retinal thickness or statistics of a specific region in the ETDRS grid, the change in retinal thickness relative to the reference examination, the area density or skeleton density of blood vessels, the amount of change in these densities due to the acquisition time interval, and the like. Note that the analysis results are not limited to the method of using the ETDRS grid. For example, the layer thickness of the entire displayed image may be displayed using a color map, and the results compared with a normal eye database may be displayed taking into account age and the like. This allows the operator to easily check the OCT en face motion contrast image that takes into account blood flow velocity along with time changes.

[0071] Furthermore, as shown in FIG. 11(b), the OCT tomographic images in each examination may be displayed simultaneously. In this case, the image processing device 209 of this embodiment may extract a pixel in the ETDRS grid where the change in area density of an image that identifiably expresses the difference between at least two images among a plurality of OCT motion contrast images having different blood flow rendering ranges is maximum, and may display the OCT tomographic image passing through the pixel in an initial state. At this time, the sector including the pixel in the ETDRS grid may be displayed so as to be distinguishable. This allows the area corresponding to the area with a large change (difference) to be included in the analysis area. Note that, in this embodiment, the pixel where the change in area density of blood vessels is maximum is extracted, but this is not limited thereto. For example, an area where pixels where the change in area density of blood vessels is equal to or greater than a threshold value are consecutive for a certain amount or more may be extracted. Furthermore, for example, a lattice-shaped grid in which the inside is divided into 3x3 blocks may be used, and the center of the grid may be displayed in an initial state so as to coincide with the center of gravity of the extracted area. Also, the OCT tomographic image passing through the center of gravity of the extracted area may be displayed in an initial state. At this time, the area may be extracted on a two-dimensional image, or on a three-dimensional image. The operator can change the OCT sectional image to be displayed by moving the indices 1004 to 1007 that indicate the acquisition positions of the OCT sectional images displayed on the frontal motion contrast image. Furthermore, by setting the indices 1004 to 1007 to move in a linked manner, when the OCT sectional image to be displayed for one examination is changed, the display can be automatically updated to the OCT sectional image of the corresponding position for another examination.

[0072] The above method enables an operator to easily check the changes over time in a difference image that clearly represents the differences between at least two of multiple OCT motion contrast images having different blood flow drawing ranges.

[0073] <Other embodiments> Although the embodiment examples have been described in detail above, the disclosed technology can be embodied as, for example, a system, an apparatus, a method, a program, or a recording medium (storage medium), etc. Specifically, the technology may be applied to a system composed of multiple devices (for example, a host computer, an interface device, an imaging device, a web application, etc.), or may be applied to an apparatus composed of a single device.

[0074] Needless to say, the object of the present invention can be achieved by the following: That is, a recording medium (or storage medium) on which is recorded a program code (computer program) of software that realizes the functions of the above-mentioned embodiments is supplied to a system or device. The storage medium is, of course, a computer-readable storage medium. Then, a computer (or a CPU or MPU) of the system or device reads and executes the program code stored in the recording medium. In this case, the program code itself read from the recording medium realizes the functions of the above-mentioned embodiments, and the recording medium on which the program code is recorded constitutes the present invention. [Explanation of symbols]

[0075] 201 OCT imaging device 209 Image Processing Device 210 Display section 211 Storage section 212 Operation section

Claims

1. An OCT data acquisition means for acquiring three or more OCT data sets at different times for the same position of the subject's eye; an OCT motion contrast image generating means for generating a plurality of OCT motion contrast images having different blood flow rendering ranges from a set of OCT data having different time intervals among the acquired OCT data; An ophthalmologic image processing device comprising: An ophthalmologic image processing device comprising an image generating means for generating a difference image that identifiably expresses the difference between at least two of a plurality of OCT motion contrast images having different blood flow drawing ranges.

2. The ophthalmologic image processing apparatus according to claim 1 , wherein the difference image is an image obtained by calculating a difference in pixel values ​​between at least two of a plurality of OCT motion contrast images having different blood flow rendering ranges.

3. 2. The ophthalmologic image processing device according to claim 1, wherein the difference image is an image obtained by dividing the pixel values ​​of one of at least two images among the multiple OCT motion contrast images having different blood flow drawing ranges by the pixel values ​​of the other image.

4. An ophthalmologic image processing device as described in any one of claims 1 to 3, characterized in that the difference image is a composite image obtained by assigning any one of different RGB channels to at least two of the multiple OCT motion contrast images having the different blood flow drawing ranges and combining the images.

5. The ophthalmologic image processing device according to any one of claims 1 to 3, characterized in that the difference image is a composite image obtained by assigning different RGB channels to a first difference image that identifiably expresses the difference between at least two of the multiple OCT motion contrast images having different blood flow drawing ranges, and one of the at least two of the multiple OCT motion contrast images having different blood flow drawing ranges.

6. 6. The ophthalmologic image processing apparatus according to claim 1, wherein the difference image is an OCT en face motion contrast image.

7. 7. The ophthalmologic image processing apparatus according to claim 1, further comprising a display control unit for displaying the difference image.

8. The ophthalmologic image processing device according to claim 7, characterized in that the display control means displays areas of the difference image where there is a large difference in a distinguishable manner in at least one image of the difference image or a plurality of OCT motion contrast images having different blood flow drawing ranges, which are displayed images on the display means.

9. 9. The ophthalmologic image processing apparatus according to claim 8, further comprising an analysis unit configured to analyze an area including an area corresponding to an area with a large difference in the differential image, out of the analysis target data related to the displayed image.

10. 10. The ophthalmologic image processing apparatus according to claim 8, wherein the OCT tomographic image of the subject's eye including at least a part of an area where the difference between the difference images is large is displayed on the display means in an initial state.

11. The ophthalmologic image processing apparatus according to claim 10 , wherein the partial region is a center of gravity of a region in which a difference between the difference images is large.

12. The OCT data includes three or more pieces of OCT data photographed at different dates and times with respect to the same position of the subject's eye, The image generating means generates a plurality of the difference images acquired at different dates and times, 12. The ophthalmologic image processing apparatus according to claim 7, wherein the display control means displays the plurality of difference images in order of acquisition date and time.

13. 13. The ophthalmologic image processing apparatus according to claim 12, wherein the display control means displays an image expressing a difference between at least two of the plurality of difference images in a identifiable manner.

14. An OCT data acquisition means for acquiring three or more OCT data sets at different times for the same position of the subject's eye; an OCT motion contrast image generating means for generating OCT motion contrast images having different blood flow rendering ranges from sets of OCT data having different time intervals among the acquired OCT data; An ophthalmological image processing program comprising: An ophthalmologic image processing device characterized by having a composite image generation means for generating a composite image by assigning different RGB channels to each of at least two of the multiple OCT motion contrast images having different blood flow drawing ranges.

15. An OCT data acquisition step of acquiring three or more OCT data sets at different times for the same position of the subject's eye; an OCT motion contrast image generating step of generating OCT motion contrast images having different blood flow rendering ranges from sets of OCT data having different time intervals among the acquired OCT data; An ophthalmological image processing program comprising: An ophthalmologic image processing program comprising an image generation step of generating a difference image that identifiably represents the difference between at least two of a plurality of OCT motion contrast images having different blood flow drawing ranges.

Images