CN102860814B - OCT (Optical Coherence Tomography) synthetic fundus image optic disc center positioning method and equipment - Google Patents

Abstract

The invention discloses an OCT (Optical Coherence Tomography) synthetic fundus image optic disc center positioning method and equipment. The OCT synthetic fundus image optic disc center positioning method comprises the following steps of: acquiring fundus image data; processing the fundus image data by utilizing a preset inner and outer square frames; calculating the correlation between a characteristic template and the fundus image by moving the characteristic template of the preset inner and outer square frames to acquire a correlation matrix; and finding the maximum numerical value point in the correlation matrix, so that a central area of the fundus image optic disc can be positioned. Data loss or high noise is not required in the fundus image acquisition, an optic disc area acquired by standard operation of an OCT instrument generally meets the characteristics that the central area of the optic disc is dark and the periphery is bright, and the optic disc area can be rapidly and accurately positioned; and therefore, the algorithm is higher in stability and higher in calculation speed and can be used for rapidly positioning and analyzing a lots of fundus images.

Description

A method and device for locating the optic disc center of an OCT synthetic fundus image

technical field

The invention belongs to the technical field of positioning, and in particular relates to a method and equipment for positioning the center of an optic disc of an OCT synthetic fundus image.

Background technique

The current optic disc center positioning technology of fundus map mainly includes: 1. Positioning of the optic disc center based on the fundus map blood vessels, but based on the direction of the blood vessels; 2. Positioning of the optic disc area based on hough circle detection and active contour model.

First, both methods are based on edge features of images, such as blood vessels and optic disc edges. However, edge detection is greatly affected by image quality, so at present, these two aspects mainly focus on non-OCT-synthesized fundus maps, such as fundus maps obtained by fundus cameras. Because the image quality of this type of fundus map is clear, blood vessels and optic disc edges are easy to locate. The overall quality of the optical coherence tomography (OCT) fundus composite image is not as good as that of the fundus color photo, and the contrast of the blood vessels and the optic disc area is weak, especially the edge of the optic disc. At the same time, the scanning time of each OCT area is longer Long, the shaking or blinking of the human eye will affect the OCT fundus image synthesized in the later stage. Therefore, these two types of methods cannot be directly applied to synthetic OCT images.

Secondly, these two methods, whether it is blood vessel thinning or edge detection, require complex algorithm design in the early stage, especially the impact of the image quality of the OCT synthetic fundus image. To produce a more accurate edge segmentation effect, the algorithm will be More complex, there will be a larger amount of calculation.

Contents of the invention

The embodiments of the present invention relate to the field of positioning technology, in particular to a method and equipment for locating the optic disc center of an OCT synthetic fundus map, which is used to quickly locate the center of the optic disc of the fundus map according to the feature that the center of the fundus map is dark and the periphery is bright.

A method for locating the optic disc center of an OCT synthetic fundus image, comprising:

Obtain fundus image data;

The fundus image data is processed by using the preset inner and outer square frames, the size of the inner and outer square frames is obtained according to the statistics of multiple sets of data obtained by manual measurement of normal human eye fundus images, and the inner frame value of the inner and outer square frames is -1 divided by the number of pixels of the inner frame, the value of the outer frame of the inner and outer square frames is 1 divided by the number of pixels of the outer frame;

By moving the feature templates of the preset inner and outer square frames, calculating the correlation between the feature templates and the fundus image to obtain a correlation matrix;

The central area of the optic disc of the fundus map can be located by finding the maximum value point in the correlation matrix.

An OCT synthetic fundus image optic disc center positioning device, comprising:

An acquisition module, configured to acquire fundus image data;

The processing module is used to process the fundus image data using the preset inner and outer square frames, the size of the inner and outer square frames is obtained according to statistics of multiple sets of data obtained by manual measurement of normal human eye fundus images, and the inner and outer square frames The value of the inner frame is -1 divided by the number of pixels of the inner frame, and the value of the outer frame of the inner and outer square frames is 1 divided by the number of pixels of the outer frame;

A calculation module, configured to calculate the correlation between the feature template and the fundus image by moving the preset feature template of the inner and outer square frames, and obtain a correlation matrix;

The positioning module is used to locate the central area of the optic disc of the fundus map by finding the point with the largest value in the correlation matrix.

Compared with the existing technology, the embodiment of the present invention does not need to consider fine blood vessels and optic disc edge features. For fundus images of different qualities, as long as the optic disc area conforms to the dark and bright features of the central area of the optic disc, the optic disc area can be quickly and accurately located , so the stability of the algorithm is strong, and at the same time, the calculation speed of the algorithm is very fast, and it can quickly locate and analyze a large number of fundus images.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For Those of ordinary skill in the art can also obtain other drawings based on these drawings without making creative efforts.

Fig. 1 is a schematic flow chart of a method for locating the optic disc center of an OCT synthetic fundus image provided by an embodiment of the present invention;

Fig. 2 is a schematic diagram of an inner and outer square matrix provided by an embodiment of the present invention;

Fig. 3 is a schematic structural diagram of an optic disc center positioning device for an OCT synthetic fundus image provided by an embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Please refer to Fig. 1. Fig. 1 is a schematic flowchart of a method for locating the optic disc center of an OCT synthetic fundus image provided by an embodiment of the present invention. As shown in Figure 1, the method for positioning the optic disc center of the fundus map includes the following steps:

101. Obtain fundus image data;

In this embodiment, there are two ways to obtain the fundus image data: first, a fundus map not synthesized by OCT, such as a fundus map obtained by a fundus camera. Because the image quality of this type of fundus map is clear, blood vessels and optic disc edges are easy to locate. Second, OCT fundus composite map. Optical correlation tomography, a high-resolution, non-contact biological tissue imaging technology, enables doctors to obtain images similar to pathological changes in ocular tissue in vivo. The overall quality of such synthetic fundus images is not as good as that of fundus color photos In the first type of fundus map, the contrast of the blood vessels and optic disc area is weak, especially the edge of the optic disc. At the same time, each OCT area scan takes a long time, and the shaking or blinking of the human eye will affect the OCT fundus map synthesized later.

At present, the scanning range of the OCT scanning instrument we use is 6×6mm. The optical correlation tomography image obtained by each scan has 492 pixels in the horizontal direction and 560 pixels in the vertical direction, that is, the A-scan is 560Pixel, and the B-scan is 492Pixel. Scan 100 times, that is, C-scan is 100. Therefore, we can obtain a planar OCT composite image from the whole data acquired by scanning, as shown in Fig. 2. Synthesis method: The average value of the pixel values of all points in each column of A-scan is used as the pixel value of a single point in the composite image. In this way, the pixel value of the entire OCT composite image is obtained, and the image is normalized and stretched, and the pixel value of the OCT composite image is stretched to between 0 and 255 to increase the contrast of the image. Preferably, the interpolation operation is performed on the synthesized image to obtain fundus image data with a size of 492×492.

In this embodiment, by normalizing and stretching the image, the pixel value of the OCT composite image is stretched to between 0-255 to increase the contrast of the image, thereby making the contrast of the original OCT data more obvious; through longitudinal A -scan can obtain the average pixel value of a single point in each column, and scan 100 times at the same time to obtain a 492×100 data matrix. After interpolating the composite image, the fundus image square data of 492×492 size is obtained, and normalized Both the stretching and interpolation operations increase the contrast of the data matrix of the OCT composite image and simultaneously turn it into a square matrix, which is easy for data processing and other operations.

102. Process the fundus image data using the preset inner and outer square frames, the size of the inner and outer square frames is obtained according to the statistics of multiple sets of data obtained by manual measurement of normal human eye fundus images, and the inner frame of the inner and outer square frames The numerical value is -1 divided by the pixel points of the inner frame, and the outer frame value of the inner and outer square frames is 1 divided by the pixel points of the outer frame;

In this embodiment, for each OCT image scanned in the B-scan direction, the pixel values of all (560) points in the A-scan direction of the optic disc area are very small, that is, there is no reflected signal. Therefore, the pixel values synthesized in this part of the region will also be very small in the synthesized image, that is, a dark region appears. Outside the optic disk area, due to the strong reflection signal, the pixel value is larger, so it appears brighter. Since the optic disc itself is similar to a circle, this makes the optic disc area appear as a darker area similar to a circle in the fundus map. Since the optic disc area is similar to a circle, we design a nested square area, the structure of which is shown in Figure 3. The size of the inner and outer frames of the above square is obtained according to the statistics of 100 groups of data obtained by manual measurement of the normal fundus map. The value of the inner frame of the above square is -1 divided by the number of pixels in the inner frame, and the value of the outer frame of the above square is 1 divided by the number of pixels in the outer frame. , where the design of the inner and outer square frames is based on the characteristics of the optic disc area, that is, the optic disc area is a dark area in the center and a bright area around it in the fundus image.

In this embodiment, the information of the OCT optic disc image is extracted by designing a nested square matrix of inner and outer frames according to the characteristics of the OCT optic disc region, so as to locate the center of the optic disc in the fundus map after operating on the image through the translation matrix.

103. Calculate the correlation between the feature template and the fundus image by moving the preset feature template of the inner and outer square frames, and obtain a correlation matrix;

In this embodiment, the translation template makes the inner and outer nested square matrix operate on the data of the entire optic disc region map. Because the inner and outer nested square matrix is designed according to the characteristics of the optic disc region map, that is, the center is dark and the periphery is bright, so by After operating on the data of the optic disc region map, a correlation matrix is obtained. The value of each point in the above correlation matrix represents the similarity between the fundus map feature and the translation template feature with the point as the center and the template area as the size, so that the information of the optic disc area can be extracted according to the similarity, and the fundus can be accurately located The central area of the disk.

104. Locate the central area of the optic disc of the fundus map by finding the point with the largest value in the correlation matrix.

In this embodiment, after processing the entire OCT visual disk image through the designed inner and outer nested square matrix and translation module, a correlation matrix is obtained, and the numerical representation of each point in the correlation matrix is centered on the store , the similarity between the features of the fundus map with the size of the template area and the features of the translation template can be located according to the maximum value point in the correlation matrix to the central area of the optic disc of the fundus map.

The embodiment of the present invention quickly locates the optic disc center of the fundus map according to the feature that the center of the optic disc region is dark and the periphery is bright. The method includes: acquiring fundus image data; designing a nested inner and outer square frame; calculating the translation template and the image by using a translation template Correlation, obtain a correlation matrix; find the point with the largest value in the matrix to locate the central area of the optic disc of the fundus map. The embodiment of the present invention does not need to consider fine blood vessels and optic disc edge features. For fundus images of different quality, as long as the optic disc area conforms to the dark and bright features of the central area of the optic disc, the optic disc area can be quickly and accurately located, so the stability of the algorithm is relatively high. At the same time, the calculation speed of the algorithm is very fast, and it can quickly locate and analyze a large number of fundus images.

Please refer to Figure 2. Figure 2 is a schematic diagram of an inner and outer square matrix provided by an embodiment of the present invention. The size of the inner and outer frames of the square is obtained according to the statistics of multiple sets of data obtained by manual measurement of normal human fundus images. The value of the inner frame of the above square is - Divide 1 by the number of pixels in the inner frame, and the value of the outer frame of the above square is 1 divided by the number of pixels in the outer frame.

In this embodiment, for each OCT image scanned in the B-scan direction, the pixel values of all (560) points in the A-scan direction of the optic disc area are very small, that is, there is no reflected signal. Therefore, the pixel values synthesized in this part of the region will also be very small in the synthesized image, that is, a dark region appears. Outside the optic disk area, due to the strong reflection signal, the pixel value is larger, so it appears brighter. Since the optic disc itself is similar to a circle, this makes the optic disc area appear as a darker area similar to a circle in the fundus map. Since the optic disc area is similar to a circle, we design a nested square area, the structure of which is shown in Figure 3. The size of the inner and outer frames of the above square is obtained according to the statistics of 100 groups of data obtained by manual measurement of the normal fundus map. The value of the inner frame of the above square is -1 divided by the number of pixels in the inner frame, and the value of the outer frame of the above square is 1 divided by the number of pixels in the outer frame. , where the design of the inner and outer square frames is based on the characteristics of the optic disc area, that is, the optic disc area is a dark area in the center and a bright area around it in the fundus image.

In this embodiment, the information of the OCT optic disc image is extracted by designing a nested square matrix of inner and outer frames according to the characteristics of the OCT optic disc region, so as to locate the center of the optic disc in the fundus map after operating on the image through the translation matrix.

Please refer to FIG. 3. FIG. 3 is a schematic structural diagram of an OCT synthetic fundus image optic disc center positioning device provided by an embodiment of the present invention. The device includes the following modules:

An acquisition module 301, configured to acquire fundus image data;

In this embodiment, there are two ways to obtain the fundus image data: first, a fundus map not synthesized by OCT, such as a fundus map obtained by a fundus camera. Because the image quality of this type of fundus map is clear, blood vessels and optic disc edges are easy to locate. Second, OCT fundus composite map. Optical correlation tomography, a high-resolution, non-contact biological tissue imaging technology, enables doctors to obtain images similar to pathological changes in ocular tissue in vivo. The overall quality of such synthetic fundus images is not as good as that of fundus color photos In the first type of fundus map, the contrast of the blood vessels and optic disc area is weak, especially the edge of the optic disc. At the same time, each OCT area scan takes a long time, and the shaking or blinking of the human eye will affect the OCT fundus map synthesized later.

At present, the scanning range of the OCT scanning instrument we use is 6×6mm. For each scan

The optical coherence tomography image has 492 pixels horizontally and 560 pixels vertically, that is, A-scan is 560Pixel and B-scan is 492Pixel. Scan 100 times, that is, C-scan is 100. Therefore, we can obtain a planar OCT composite image from the whole data acquired by scanning, as shown in Fig. 2. Synthesis method: The average value of the pixel values of all points in each column of A-scan is used as the pixel value of a single point in the composite image. In this way, the pixel value of the entire OCT composite image is obtained, and the image is normalized and stretched, and the pixel value of the OCT composite image is stretched to between 0 and 255 to increase the contrast of the image. Preferably, the interpolation operation is performed on the synthesized image to obtain fundus image data with a size of 492×492.

In this embodiment, by normalizing and stretching the image, the pixel value of the OCT composite image is stretched to between 0-255 to increase the contrast of the image, thereby making the contrast of the original OCT data more obvious; through longitudinal A -scan can obtain the average pixel value of a single point in each column, and scan 100 times at the same time to obtain a 492×100 data matrix. After interpolating the composite image, the fundus image square data of 492×492 size is obtained, and normalized Both the stretching and interpolation operations increase the contrast of the data matrix of the OCT composite image and simultaneously turn it into a square matrix, which is easy for data processing and other operations.

The processing module 302 is configured to process the fundus image data using a preset inner and outer square frame, the size of the inner and outer square frame is obtained according to the statistics of multiple sets of data obtained by manual measurement of normal human eye fundus images, and the inner and outer square frame The value of the inner frame of the frame is -1 divided by the number of pixels of the inner frame, and the value of the outer frame of the inner and outer square frame is 1 divided by the number of pixels of the outer frame;

In this embodiment, for each OCT image scanned in the B-scan direction, the pixel values of all (560) points in the A-scan direction of the optic disc area are very small, that is, there is no reflected signal. Therefore, the pixel values synthesized in this part of the region will also be very small in the synthesized image, that is, a dark region appears. Outside the optic disk area, due to the strong reflection signal, the pixel value is larger, so it appears brighter. Since the optic disc itself is similar to a circle, this makes the optic disc area appear as a darker area similar to a circle in the fundus map. Since the optic disc area is similar to a circle, we design a nested square area, the structure of which is shown in Figure 3. The size of the inner and outer frames of the above square is obtained according to the statistics of 100 groups of data obtained by manual measurement of the normal fundus map. The value of the inner frame of the above square is -1 divided by the number of pixels in the inner frame, and the value of the outer frame of the above square is 1 divided by the number of pixels in the outer frame. , where the design of the inner and outer square frames is based on the characteristics of the optic disc area, that is, the optic disc area is a dark area in the center and a bright area around it in the fundus image.

In this embodiment, the information of the OCT optic disc image is extracted by designing a nested square matrix of inner and outer frames according to the characteristics of the OCT optic disc region, so that after the image is operated on through the translation matrix, the positioning of the eye

The basemap's optic disc center.

Calculation module 303, configured to calculate the correlation between the feature template and the fundus image by moving the preset feature template of the inner and outer square frames, and obtain a correlation matrix;

In this embodiment, the translation template makes the inner and outer nested square matrix operate on the data of the entire optic disc region map. Because the inner and outer nested square matrix is designed according to the characteristics of the optic disc region map, that is, the center is dark and the periphery is bright, so by After operating on the data of the optic disc region map, a correlation matrix is obtained. The value of each point in the above correlation matrix represents the similarity between the fundus map feature and the translation template feature with the point as the center and the template area as the size, so that the information of the optic disc area can be extracted according to the similarity, and the fundus can be accurately located The central area of the disk.

The positioning module 304 is used to locate the central area of the optic disc of the fundus map by finding the point with the largest value in the matrix.

In this embodiment, after processing the entire OCT visual disk image through the designed inner and outer nested square matrix and translation module, a correlation matrix is obtained, and the numerical representation of each point in the correlation matrix is centered on the store , the similarity between the features of the fundus map with the size of the template area and the features of the translation template can be located according to the maximum value point in the correlation matrix to the central area of the optic disc of the fundus map.

The embodiment of the present invention quickly locates the center of the optic disc of the fundus map according to the feature that the center of the fundus map is dark and the periphery is bright. The device includes: an acquisition module 301 for acquiring fundus image data; a processing module 302 for designing a nested inner and outer square frame; The calculation module 303 is used to calculate the correlation between the translation template and the image through the translation template, and obtain a correlation matrix; the positioning module 304 can locate the central area of the optic disc of the fundus image by finding the point with the largest value in the matrix. The embodiment of the present invention does not need to consider fine blood vessels and optic disc edge features. For fundus images of different quality, as long as the optic disc area conforms to the dark and bright features of the central area of the optic disc, the optic disc area can be quickly and accurately located, so the stability of the algorithm is relatively high. At the same time, the calculation speed of the algorithm is very fast, and it can quickly locate and analyze a large number of fundus images.

The above descriptions are only preferred embodiments of the present invention, and do not constitute a limitation to the protection scope of the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the scope of the claims of the present invention.

Claims (10)

1. an OCT synthetic fundus map optic disc center location method, is characterized in that, described method comprises: Obtain fundus image data; The fundus image data is processed by using the preset inner and outer square frames, the size of the inner and outer square frames is obtained according to the statistics of multiple sets of data obtained by manual measurement of normal human eye fundus images, and the inner frame value of the inner and outer square frames is -1 divided by the number of pixels of the inner frame, the value of the outer frame of the inner and outer square frames is 1 divided by the number of pixels of the outer frame; By moving the feature templates of the preset inner and outer square frames, calculating the correlation between the feature templates and the fundus image to obtain a correlation matrix; The central area of the optic disc of the fundus map can be located by finding the maximum value point in the correlation matrix. 2. The method according to claim 1, wherein said obtaining fundus image data comprises: Do a 6mm linear scan on the optic disc area of the human eye to obtain an OCT image with 492 pixels in the horizontal direction and 560 pixels in the vertical direction. The horizontal direction is the scanning width, which actually corresponds to 6mm. The vertical direction is the scanning depth. direction, do 100 linear scans at a distance of 0.06mm to obtain 100 OCT scan images, and use the average value of the pixel values of all points in the longitudinal direction of each column as the pixel value of a single point of the synthetic fundus image to obtain the entire fundus image. Pixel value, normalized stretching of the fundus image, stretching the pixel value of the fundus image to between 0 and 255, increasing the contrast of the fundus image, thereby obtaining 492 pixels in the horizontal direction and 100 pixels in the vertical direction rough fundus image. 3. The method according to claim 2, wherein the method further comprises: Since the actual measured data is a square area of 6 mm, cubic spline interpolation is performed on the fundus image to obtain fundus image data with a size of 492×492. 4. The method according to claim 1, wherein the design of the inner and outer square frames is designed according to the characteristics of the optic disc region, and the characteristic of the optic disc region is that the center of the fundus image is dark and the periphery is bright. 5. The method according to claim 1, wherein the value of each point in the correlation matrix is the similarity between the fundus map feature and the feature template feature centered on the point and taking the template area as the size. 6. An OCT synthetic fundus map optic disc center positioning device, characterized in that the device comprises: An acquisition module, configured to acquire fundus image data; The processing module is used to process the fundus image data using the preset inner and outer square frames, the size of the inner and outer square frames is obtained according to the statistics of multiple sets of data obtained by manual measurement of normal human eye fundus images, and the inner and outer square frames The value of the inner frame is -1 divided by the number of pixels of the inner frame, and the value of the outer frame of the inner and outer square frames is 1 divided by the number of pixels of the outer frame; A calculation module, configured to calculate the correlation between the feature template and the fundus image by moving the preset feature template of the inner and outer square frames, and obtain a correlation matrix; The positioning module is used to locate the central area of the optic disc of the fundus map by finding the point with the largest value in the correlation matrix. 7. The device according to claim 6, wherein the acquiring module comprises: Do a 6mm linear scan on the optic disc area of the human eye to obtain an OCT image with 492 pixels in the horizontal direction and 560 pixels in the vertical direction. The horizontal direction is the scanning width, which actually corresponds to 6mm. The vertical direction is the scanning depth. direction, do 100 linear scans at a distance of 0.06mm to obtain 100 OCT scan images, and use the average value of the pixel values of all points in the longitudinal direction of each column as the pixel value of a single point of the synthetic fundus image to obtain the entire fundus image. Pixel value, normalized stretching of the fundus image, stretching the pixel value of the fundus image to between 0 and 255, increasing the contrast of the fundus image, thereby obtaining 492 pixels in the horizontal direction and 100 pixels in the vertical direction rough fundus image. 8. The device according to claim 7, wherein said obtaining fundus image data in said obtaining module further comprises: Since the actual measured data is a square area of 6 mm, cubic spline interpolation is performed on the fundus image to obtain fundus image data with a size of 492×492. 9. The device according to claim 6, wherein the design of the inner and outer square frames is designed according to the characteristics of the optic disc region, which is that the center of the fundus image is dark and the periphery is bright. 10. The device according to claim 6, wherein the value of each point in the correlation matrix is the similarity between the feature of the fundus map and the feature template feature centered at the point and taking the template area as the size.