Corneal thickness detection method after cataract phacoemulsification based on previous section OCT

Abstract

This application discloses a method for detecting corneal thickness after phacoemulsification cataract surgery based on anterior segment OCT, belonging to the field of image analysis technology. The method includes: dividing the cornea into multiple first regions based on a region growing algorithm and initial corneal thickness data; obtaining second regions based on each first region; obtaining multiple partial boundaries based on the second regions; obtaining fibrotic regions based on each partial boundary; and adjusting the scanning density and refractive index of the second regions based on the fibrotic regions and a scanning density correction coefficient to obtain the final corneal thickness data. This application combines the fibrotic regions and the scanning density correction coefficient to adjust the scanning density and refractive index of the second regions, avoiding the errors of calculations using a uniform refractive index in existing technologies, ultimately achieving accurate measurement of corneal thickness and solving the technical problem that existing OCT detection cannot accurately measure corneal regional thickness.

Description

Technical Field

[0001] This application relates to the field of image analysis technology, specifically a method for detecting corneal thickness after phacoemulsification cataract surgery based on anterior segment OCT. Background Technology

[0002] Anterior segment OCT detection, based on different regional divisions, provides a comprehensive understanding of corneal recovery after phacoemulsification cataract surgery, accurately comparing the dynamic changes in corneal thickness in local areas such as the central zone and the peri-incision zone. It can also locate abnormal areas and easily detect complications such as incision dehiscence and Descemet's membrane detachment. Furthermore, high-resolution non-contact imaging avoids mechanical damage, providing targeted intervention for patients with poor incision healing. Current OCT detection techniques use a uniform scanning array and measure the thickness of the entire corneal area with the same refractive index, resulting in inaccurate data. Summary of the Invention

[0003] The purpose of this application is to provide a method for measuring corneal thickness after phacoemulsification cataract surgery based on anterior segment OCT, so as to solve the technical problem that existing OCT detection cannot accurately measure the thickness of the corneal region.

[0004] To achieve the above objectives, this application provides the following technical solution:

[0005] This application proposes a technical solution for measuring corneal thickness after phacoemulsification cataract surgery based on anterior segment OCT. This method includes:

[0006] Based on the region growing algorithm and initial corneal thickness data, the cornea is divided into multiple first regions; the initial corneal thickness data is obtained in advance.

[0007] Obtain the scanning density correction coefficient corresponding to each first region; the scanning density correction coefficient is at least positively correlated with the degree of corneal thickness non-uniformity in the corresponding first region;

[0008] Based on each first region, a second region is obtained; the second region is any first region whose scan density correction coefficient is greater than a first preset value.

[0009] Based on the second region, multiple partial boundaries are obtained; the partial boundaries are the boundaries formed by connecting the first scan point and the second scan point; the first scan point and the second scan point are any two adjacent scan points in the second region, and the degree of similarity between the first scan point and the second scan point is greater than a second preset value; the degree of similarity is positively correlated with the similarity of the thickness abrupt change features between the first scan point and the second scan point.

[0010] Based on the boundaries of each part, obtain the fibrous region;

[0011] Based on the fibrotic region and the scanning density correction coefficient, the scanning density and refractive index of the second region are adjusted to obtain the final corneal thickness data.

[0012] As a specific solution in this application, the initial corneal thickness data is acquired in advance, including:

[0013] Based on the anterior segment OCT device, multiple scans are performed on different locations of the cornea according to a preset scanning matrix to obtain multiple first test results;

[0014] Based on each first test result, multiple second test results are obtained; the second test result is the test result in which the signal strength of each first test result is greater than a third preset value.

[0015] The initial corneal thickness data is obtained based on the average value of each second test result.

[0016] As a specific solution in this application, obtaining the scanning density correction coefficients corresponding to each first region includes:

[0017] Based on each first region, a third region is obtained; the third region is any region in each first region for which no corresponding scan density correction coefficient has been obtained;

[0018] Based on the third region, a first thickness value and a second thickness value are obtained; the first thickness value is the maximum thickness value corresponding to each scanning point in the third region; the second thickness value is the minimum thickness value corresponding to each scanning point in the third region.

[0019] Based on the first thickness value and the second thickness value, the scanning density correction coefficient corresponding to the third region is obtained.

[0020] As a specific solution in this application, after obtaining the scanning density correction coefficient corresponding to the third region based on the first thickness value and the second thickness value, the method further includes:

[0021] Based on the third region, multiple third thickness values ​​are obtained; the third thickness values ​​are the thickness values ​​of the corresponding scanning points in the third region.

[0022] Based on each third thickness value, a first sequence is obtained; the third thickness values ​​in the first sequence are arranged in ascending order.

[0023] Based on the first sequence, obtain the difference sequence;

[0024] Based on the difference sequence, the first sequence is divided into multiple second sequences;

[0025] Based on each second sequence, obtain a first quantity and a second quantity; the first quantity is the number of sequences with the most values ​​in each second sequence; the second quantity is the number of each second sequence.

[0026] Based on the first quantity and the second quantity, an adjustment coefficient is obtained; the adjustment coefficient is used to correct the scan density correction coefficient corresponding to the third region.

[0027] As a specific solution in this application, the step of dividing the first sequence into multiple second sequences based on the difference sequence includes:

[0028] Based on the difference sequence, multiple abnormal sequence values ​​are obtained; the abnormal sequence value is any sequence value in the difference sequence that is greater than a fourth preset value.

[0029] Based on each abnormal sequence value, obtain the minuend and subtrahend corresponding to each abnormal sequence value;

[0030] Based on the minuend and the subtrahend, the first sequence is divided into multiple second sequences; wherein the subtrahend belongs to the first second sequence and the minuend belongs to the second sequence.

[0031] As a specific solution in this application, the method for obtaining the thickness abrupt change feature of the first scanning point includes:

[0032] Based on the first scanning point, a third scanning point is obtained; the third scanning point is the scanning point with the largest difference in corneal thickness among the eight neighboring scanning points of the first scanning point.

[0033] Based on the first scan point and the third scan point, a first difference and a first direction are obtained; the first difference is the difference in corneal thickness corresponding to the first scan point and the third scan point; the first direction is the direction from the first scan point to the third scan point.

[0034] Based on the first difference and the first direction, the thickness abrupt change feature of the first scanning point is obtained.

[0035] As a specific solution in this application, the method for obtaining the degree of agreement value between the first scan point and the second scan point includes:

[0036] Based on the second scan point, a second difference and a second direction are obtained; the second difference and the second direction are the thickness abrupt change features corresponding to the second scan point;

[0037] Based on the first difference and the second difference, a third difference is obtained; the third difference is the absolute value of the difference between the first difference and the second difference.

[0038] Based on the first direction and the second direction, a fourth difference is obtained; the fourth difference is the maximum rotation angle difference between the first direction and the second direction under different rotation angles of Euler angles.

[0039] Based on the third difference and the fourth difference, the degree of agreement between the first scan point and the second scan point is obtained.

[0040] As a specific solution in this application, the step of obtaining the fibrous region based on the boundaries of each part includes:

[0041] Based on the boundaries of each part, obtain the complete boundary;

[0042] Based on the complete boundary, a first mean and a second mean are obtained; the first mean is the average thickness of adjacent scan points on the outer periphery of the complete boundary; the second mean is the average thickness of all scan points outside the area enclosed by the complete boundary in the second region.

[0043] Based on the complete boundary, a third quantity and a fourth quantity are obtained; the third quantity is the total number of scan points contained in each partial boundary; the fourth quantity is the total number of scan points contained in the complete boundary.

[0044] Based on the first mean, the second mean, the third quantity, and the fourth quantity, a consistency value corresponding to the region enclosed by the complete boundary is obtained; the consistency value is negatively correlated with the absolute value of the difference between the first mean and the second mean, and positively correlated with the ratio of the third quantity to the fourth quantity;

[0045] The region enclosed by the complete boundary with the highest consistency value is defined as the fibrotic region.

[0046] As a specific solution in the technical solution of this application, the step of obtaining the complete boundary based on the boundaries of each part includes:

[0047] Based on the boundaries of each part, the mean thickness change value corresponding to each part boundary is obtained; the mean thickness change value is the average of the thickness difference values ​​in the thickness change features of all scanning points in that part boundary.

[0048] The boundary regions where the mean difference of thickness mutation is less than or equal to the fifth preset value are divided into the same group;

[0049] For any part of the boundary in each group, obtain its head scan point and tail scan point;

[0050] Based on the head scan point, the adjacent scan point with the highest degree of correspondence with the head scan point is selected in the second region, and the adjacent scan point is added to the head of the partial boundary; based on the tail scan point, the adjacent scan point with the highest degree of correspondence with the tail scan point is selected in the second region, and the adjacent scan point is added to the tail of the partial boundary; until the partial boundary forms a closed boundary, the closed boundary is the complete boundary.

[0051] As a specific solution in this application, the adjustment of the refractive index of the second region based on the fibrous region includes:

[0052] Based on the fibrous region, an area value and a fourth thickness value are obtained; the area value is the area of ​​the fibrous region; the fourth thickness value is the maximum thickness value corresponding to each scanning point in the fibrous region.

[0053] Based on the second region, a fifth thickness value is obtained; the fifth thickness value is the average thickness of all scanning points outside the fibrotic region in the second region.

[0054] Based on the area value, the fourth thickness value, and the fifth thickness value, a refractive index correction coefficient is obtained; the refractive index correction coefficient is positively correlated with the area value and positively correlated with the difference between the fourth thickness value and the fifth thickness value.

[0055] Based on the refractive index correction coefficient and the preset reference refractive index, the target refractive index corresponding to the fibrous region is obtained;

[0056] The refractive index of the fibrous region is adjusted to the target refractive index.

[0057] Compared with the prior art, the beneficial effects of this application are:

[0058] This application, based on a region growing algorithm and initial corneal thickness data, divides the cornea into multiple first regions, achieving refined corneal partitioning and avoiding the coarseness of overall uniform processing. By obtaining a scan density correction coefficient positively correlated with the corneal thickness non-uniformity of each first region, second regions with scan density correction coefficients greater than a first preset value are selected. Scanning is optimized for these second regions, addressing the problem that existing uniform scan arrays cannot adapt to areas of thickness difference. By identifying adjacent scan points with similar thickness abrupt change characteristics within the second region to form partial boundaries, fibrotic areas are determined, accurately locating postoperative abnormal areas. Combining the fibrotic areas and scan density correction coefficients, the scan density and refractive index of the second regions are adjusted, avoiding the errors of calculations using a uniform refractive index in existing technologies. Ultimately, this achieves accurate measurement of corneal thickness, solving the technical problem that existing OCT detection cannot accurately measure corneal regional thickness. Attached Figure Description

[0059] Figure 1 This is a schematic flowchart of a method for detecting corneal thickness after phacoemulsification cataract surgery based on anterior segment OCT, as proposed in an embodiment of this application. Detailed Implementation

[0060] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0061] The terms "first," "second," etc., used in the specification and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. For example, the first region and the second region mentioned below belong to different regions. It should be understood that such names can be used interchangeably where appropriate so that the embodiments described herein can be implemented in a sequence other than that illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or modules is not necessarily limited to those steps or modules explicitly listed, but may include other steps or modules not explicitly listed or inherent to these processes, methods, products, or devices. The division of modules in the embodiments of this application is merely a logical division. In actual applications, there may be other division methods. For example, multiple modules may be combined into or integrated into another system, or some features may be ignored or not performed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be through some interface, and the indirect coupling or communication connection between modules may be electrical or other similar forms. None of these are limited in the embodiments of this application. Furthermore, the modules or sub-modules described as separate components may or may not be physically separate, may or may not be physical modules, or may be distributed among multiple circuit modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the embodiments of this application.

[0062] To address the technical problem mentioned in the background art that existing OCT detection methods cannot accurately measure corneal thickness, this application proposes an embodiment of a method for measuring corneal thickness after phacoemulsification cataract surgery based on anterior segment OCT. For example... Figure 1 As shown, the method for detecting corneal thickness after phacoemulsification cataract surgery based on anterior segment OCT includes steps S100 to S600.

[0063] Step S100: Based on the region growth algorithm and the initial corneal thickness data, the cornea is divided into multiple first regions.

[0064] In this embodiment, the initial corneal thickness data is acquired in advance. For example, the initial corneal thickness data can be acquired by direct reading (e.g., directly extracted from stored historical detection data, detection results from other devices, or preprocessed valid data). Alternatively, the initial corneal thickness data is acquired in advance, including steps S110 to S130.

[0065] It's important to understand that the basic logic of the region growing algorithm is to start from an initial seed point or region and, according to a specific similarity criterion (primarily based on the similarity of corneal thickness features in this method), gradually merge neighboring pixels or scan points that meet the conditions into the initial region, ultimately forming multiple independent regions (i.e., the first region) with similar attributes. Region growing algorithms are mature technologies and will not be elaborated upon here.

[0066] Step S110: Based on the anterior segment OCT device, perform multiple scans on different locations of the cornea according to the preset scanning matrix to obtain multiple first test results.

[0067] It is important to understand that anterior segment OCT is an ophthalmic examination device based on optical coherence tomography (OCT) technology, primarily used for high-resolution, non-invasive imaging and analysis of the anterior segment structures of the eye.

[0068] In this embodiment, the first test result refers to the multiple raw scan results obtained after the anterior segment OCT device performs multiple scans on different locations of the cornea according to a preset scanning matrix. It should be noted that the raw scan results are the initial, unprocessed data, which may contain inaccurate data due to insufficient signal strength or other interference factors. Therefore, these unstable data need to be removed in step S120.

[0069] In this embodiment, during data acquisition, the patient's chin should be placed on the chin pad of the anterior segment OCT instrument, with the forehead pressed firmly against the forehead rest to avoid head tilting. The patient fixates on the target (usually a green light source), and the operator adjusts the eye position using real-time imaging to ensure the cornea is centered within the positioning frame. If the patient's eyelids are obstructing the view, the upper eyelid should be pulled back with a cotton swab to ensure a corneal exposure diameter ≥6mm. The operation should be performed in a dark room to avoid stray light interfering with the signal. The reflected light band of the equipment should be calibrated before each measurement to ensure uniform brightness.

[0070] Step S120: Based on each first test result, obtain multiple second test results.

[0071] In this embodiment, the second test result is the test result in which the signal strength of each first test result is greater than a third preset value. In this embodiment, the third preset value can be set according to requirements, for example, the third preset value can be 20dB or 25dB, etc.

[0072] Step S130: Obtain the initial corneal thickness data based on the average value of each second test result.

[0073] In this embodiment, the average value of each second test result is the initial corneal thickness data. To facilitate the processing and region division of the initial corneal thickness data based on the region growing algorithm, in this embodiment, the initial corneal thickness data can be a heatmap of corneal thickness distribution.

[0074] As is known from the background art, existing OCT detection techniques use a uniform scanning array and measure the thickness of the entire corneal region with the same refractive index, resulting in inaccurate data. To obtain an accurate corneal thickness, step S200 is also required in this embodiment.

[0075] Step S200: Obtain the scanning density correction coefficients corresponding to each first region.

[0076] In this embodiment, the scanning density correction coefficient is at least positively correlated with the degree of corneal thickness non-uniformity in the corresponding first region.

[0077] In the embodiments of this application, the scanning density correction coefficients corresponding to each first region can be obtained in any reasonable manner. For example, the variance or standard deviation of each corneal thickness value in the first region can be directly used as the scanning density correction coefficient. It should be noted that the variance and standard deviation reflect the overall dispersion of all thickness values ​​in the region, which is easily affected by the uniformity of data distribution and may mask the most significant thickness differences in the region (e.g., the difference between the local maximum thickness and minimum thickness), causing the correction coefficient to fail to accurately correlate with the core feature of "thickness non-uniformity". Based on this, step S200, obtaining the scanning density correction coefficients corresponding to each first region, includes steps S210 to S230.

[0078] Step S210: Obtain the third region based on each first region.

[0079] In this embodiment, the third region is any region in each of the first regions where the corresponding scan density correction coefficient has not been obtained. That is, in this embodiment, the method for obtaining the scan density correction coefficient of any region in each of the first regions is the same as the method for obtaining the scan density correction coefficient of the third region.

[0080] Step S220: Based on the third region, obtain the first thickness value and the second thickness value.

[0081] In this embodiment, the first thickness value is the maximum thickness value corresponding to each scanning point in the third region. The second thickness value is the minimum thickness value corresponding to each scanning point in the third region.

[0082] Step S230: Based on the first thickness value and the second thickness value, obtain the scanning density correction coefficient corresponding to the third region.

[0083] In this embodiment, the scanning density correction coefficient corresponding to the third region can be obtained in any reasonable way based on the first thickness value and the second thickness value. For example, the scanning density correction coefficient can be the difference or ratio between the first thickness value and the second thickness value.

[0084] In this embodiment, the difference or ratio between the maximum and minimum thickness values ​​can intuitively and significantly reflect the most extreme thickness differences within a region, making the positive correlation between the scan density correction coefficient and the "degree of thickness non-uniformity" more accurate (i.e., the greater the difference, the larger the correction coefficient), avoiding the weakening of correlation caused by the overall discreteness of variance or standard deviation calculations. It is important to note that the difference or ratio between the maximum and minimum thickness values ​​only reflects the most extreme thickness differences within the region (i.e., the third region), and does not consider the distribution pattern of intermediate thickness values ​​(e.g., whether most thickness values ​​are concentrated in a certain range, or whether there are multiple discrete thickness clusters). For example, two regions may have the same maximum and minimum thickness values ​​and the same difference or ratio, but the thickness values ​​in one region may be concentrated in a certain interval (with only a few points being extreme values), while the thickness values ​​in the other region may be scattered across multiple intervals. In this case, using only the difference or ratio between the maximum and minimum thickness values ​​will yield the same correction coefficient, failing to distinguish the actual differences in thickness non-uniformity between the two regions. Based on this, in one embodiment of this application, after obtaining the scanning density correction coefficient corresponding to the third region based on the first thickness value and the second thickness value in step S230, the method may further include steps S240 to S290.

[0085] Step S240: Based on the third region, obtain multiple third thickness values.

[0086] In this embodiment, the third thickness value is the thickness value of the corresponding scan point in the third region. That is, in this embodiment, multiple third thickness values ​​are the thickness values ​​corresponding to all scan points in the third region.

[0087] Step S250: Obtain the first sequence based on each third thickness value.

[0088] In this embodiment, the third thickness values ​​in the first sequence are arranged in ascending order.

[0089] Step S260: Based on the first sequence, obtain the difference sequence.

[0090] In this embodiment, the difference sequence refers to the sequence formed by the difference between two adjacent sequence values ​​in the first sequence (the sequence value with the later sequence number is the minuend, and the sequence value with the earlier sequence number is the subtrahend). Obtaining the difference sequence corresponding to a certain sequence (i.e., the first sequence) is a mature technology and will not be elaborated here.

[0091] Step S270: Based on the difference sequence, divide the first sequence into multiple second sequences.

[0092] In embodiments of this application, the first sequence can be divided into multiple second sequences based on the difference sequence in any reasonable manner. For example, in one embodiment of this application, the first sequence can be segmented by calculating the cumulative sum of the difference sequences. For example, when the cumulative sum in the difference sequences exceeds a certain threshold (e.g., 2 or 3), the first sequence is segmented, focusing on capturing the "overall difference" formed by multiple consecutive small differences. In another embodiment of this application, step S270, dividing the first sequence into multiple second sequences based on the difference sequence, includes steps S271 to S273.

[0093] Step S271: Based on the difference sequence, obtain multiple abnormal sequence values.

[0094] In this embodiment, the abnormal sequence value is any sequence value in the difference sequence that is greater than the fourth preset value. In this embodiment, the implementer can adjust it according to the specific implementation environment. For example, the fourth preset value can be 0.05mm or 0.10mm. The larger the fourth preset value is set, the higher the tolerance for thickness changes. Only a very small number of significant thickness jumps are considered abnormal. The fewer the number of second sequences, the more likely the assessment of thickness non-uniformity will be biased towards the macroscopic and ignore small fluctuations. Conversely, the smaller the fourth preset value is set, the more sensitive it is to thickness changes. Small thickness differences will also be judged as abnormal. The more the number of second sequences is set, the more detailed the capture of local thickness fluctuations can be, but it is also more susceptible to noise interference.

[0095] Step S272: Based on each abnormal sequence value, obtain the minuend and subtrahend corresponding to each abnormal sequence value.

[0096] In this embodiment, the minuend is the sequence value with the later index in the first sequence corresponding to the abnormal sequence value; the subtrahend is the sequence value with the earlier index in the first sequence corresponding to the abnormal sequence value.

[0097] Step S273: Based on the minuend and the subtrahend, divide the first sequence into multiple second sequences.

[0098] In this embodiment, the subtrahend belongs to the preceding second sequence, and the minuend belongs to the following second sequence. Specifically, if the number of abnormal sequence values ​​is n, where n is an integer greater than or equal to 0, then the number of second sequences is n+1.

[0099] Step S280: Based on each second sequence, obtain the first quantity and the second quantity.

[0100] In this embodiment, the first quantity is the number of sequences with the most frequent values ​​in each second sequence. The second quantity is the number of sequences in each second sequence.

[0101] Step S290: Obtain the adjustment coefficient based on the first quantity and the second quantity.

[0102] In this embodiment, the adjustment coefficient can be obtained based on the first quantity and the second quantity in any reasonable manner. For example, the adjustment coefficient can be the ratio of the first quantity to the second quantity, or the adjustment coefficient can be a positive correlation between the ratio of the first quantity and the second quantity. In this embodiment, by sorting the thickness values ​​(i.e., the third thickness values) in the third region into a first sequence, dividing the first sequence into multiple second sequences based on the difference sequence of the first sequence, and calculating the adjustment coefficient by combining the "maximum number of sequence values ​​(first quantity)" and the "number of sequences (second quantity)" of each second sequence, the overall thickness distribution characteristics outside of extreme values ​​are quantified.

[0103] In this embodiment, the adjustment coefficient is used to correct the scan density correction coefficient corresponding to the third region. Specifically, the calculation formula for the scan density correction coefficient can be as follows:

[0104] ;

[0105] in, Indicates the scan density correction factor; Indicates the first thickness value; Indicates the second thickness value; Indicates the first quantity; This represents the second quantity. In this embodiment, in the formula... The part directly reflects the most extreme thickness difference within the region (i.e., the difference between the maximum and minimum thickness values), ensuring that the scan density correction coefficient can capture the most significant thickness inhomogeneities (e.g., areas that suddenly thicken or thin). In the formula... The adjustment factor quantifies the distribution pattern of intermediate thickness values ​​within a region. If the thickness values ​​are concentrated in a few intervals (i.e.,...) big, If the thickness value is small, the adjustment coefficient will be smaller, meaning the adjustment coefficient will weaken the original correction coefficient (indicating that the actual unevenness of the thickness value in the third region is relatively low); if the thickness value is distributed across multiple intervals (i.e., ... Small, If the thickness difference is large, the adjustment coefficient will be larger, meaning the adjustment coefficient will strengthen the original correction coefficient (indicating that the actual thickness unevenness of the third region is relatively high). This embodiment uses a combination of the most extreme thickness difference within the region and the adjustment coefficient, which avoids the one-sidedness of ignoring the intermediate distribution by using only extreme values, and also avoids the problem of masking local significant differences by using only the overall dispersion (e.g., variance or standard deviation).

[0106] Step S300: Obtain the second region based on each first region.

[0107] In this embodiment, the second region is any first region whose scan density correction coefficient is greater than a first preset value. In this embodiment, the first preset value can be set according to requirements, for example, the first preset value can be 0.5 or 0.6, etc.

[0108] Step S400: Based on the second region, obtain multiple partial boundaries.

[0109] In this embodiment, the partial boundary is the boundary formed by the line connecting the first scan point and the second scan point. The first scan point and the second scan point are any two adjacent scan points in the second region, and the similarity value between the first scan point and the second scan point is greater than a second preset value. The similarity value is positively correlated with the similarity of the thickness abrupt change features between the first scan point and the second scan point.

[0110] In this embodiment, the second preset value can be set according to requirements. For example, the second preset value can be 0.7 or 0.8, etc.

[0111] In this embodiment, the method for obtaining the thickness abrupt change feature of the first scanning point includes steps S410 to S430.

[0112] Step S410: Obtain the third scan point based on the first scan point.

[0113] In this embodiment, the third scanning point is the scanning point with the largest difference in corneal thickness among the eight neighboring scanning points of the first scanning point.

[0114] It is important to understand that the eight neighboring scan points of a given scan point (e.g., the first scan point) refer to the scan points adjacent to it in eight directions around that scan point. From a spatial perspective, if the first scan point is considered as a point in a planar coordinate system with coordinates (x, y), then the coordinates of its eight neighboring scan points are (x±1, y), (x, y±1), and (x±1, y±1), which include the four orthogonal directions (up, down, left, and right) and the four diagonal directions (upper left, upper right, lower left, and lower right) adjacent scan points.

[0115] Step S420: Based on the first scan point and the third scan point, obtain the first difference and the first direction.

[0116] In this embodiment, the first difference is the difference in corneal thickness corresponding to the first scan point and the third scan point. The first direction is the direction from the first scan point to the third scan point.

[0117] Step S430: Based on the first difference and the first direction, obtain the thickness abrupt change feature of the first scanning point.

[0118] In this embodiment, the first difference and the first direction can be used as the thickness abrupt change characteristics of the first scanning point. For example, if the first difference corresponding to the first scanning point is 200 μm and the direction is 45°, it indicates that there is a feature of a sudden decrease in corneal thickness along the upper right direction at the first scanning point; or, if the first difference corresponding to the first scanning point is -200 μm and the direction is 270°, it indicates that there is a feature of a sudden increase in corneal thickness along the downward direction at the first scanning point.

[0119] In this embodiment, the method for obtaining the degree of conformity between the first scan point and the second scan point includes steps S440 to S470.

[0120] Step S440: Based on the second scan point, obtain the second difference and the second direction.

[0121] In this embodiment, the second difference and the second direction are the thickness abrupt change features corresponding to the second scanning point.

[0122] Step S450: Obtain a third difference based on the first difference and the second difference.

[0123] In this embodiment, the third difference is the absolute value of the difference between the first difference and the second difference. For example, if the first difference is 200 μm and the second difference is 150 μm, then the third difference is 50 μm; or, if the first difference is 150 μm and the second difference is 200 μm, then the third difference is also 50 μm.

[0124] Step S460: Obtain a fourth difference based on the first direction and the second direction.

[0125] In this embodiment, the fourth difference is the maximum rotation angle difference between the first direction and the second direction under different Euler angle rotation angles. For example, if the first direction is the "upper right corner direction" (i.e., the corresponding Euler angle is 45°), and the second direction is the "direction to the right" (i.e., the corresponding Euler angle is 0°), the fourth difference is the maximum rotation angle difference between the two directions under different Euler angle rotation angles. Since the angle rotation in Euler angles has a period of 360°, the supplementary angle of the minimum rotation angle (i.e., the maximum rotation angle difference) is taken when calculating the angle between the two directions. Since the direct angle between the two directions is 45° - 0° = 45°, the maximum rotation angle difference is 360° - 45° = 315°, that is, the fourth difference is 315°.

[0126] Step S470: Based on the third difference and the fourth difference, obtain the degree of agreement between the first scan point and the second scan point.

[0127] In this embodiment, the degree of conformity between the first scan point and the second scan point can be obtained based on the third difference and the fourth difference in any reasonable manner. For example, in one embodiment of this application, step S470, based on the third difference and the fourth difference, calculates the degree of conformity between the first scan point and the second scan point using the following formula:

[0128] ;

[0129] in, This indicates the degree of agreement between the first scan point and the second scan point; Indicates the third difference; Indicates the fourth difference; This represents a normalization function used to normalize the values ​​within the parentheses to the range [0, 1].

[0130] In one embodiment of this application, step S470, based on the third difference and the fourth difference, obtains the following formula for calculating the degree of conformity between the first scan point and the second scan point:

[0131] ;

[0132] in, This indicates the degree of agreement between the first scan point and the second scan point; Indicates the third difference; Indicates the fourth difference; It represents an exponential function with the natural constant as the base; 'a' represents the zero-prevention coefficient, which is any positive number close to 0. For example, the zero-prevention coefficient 'a' can be 0.01 or 0.001, etc.

[0133] In this embodiment, the conformity score is used to measure the similarity of thickness abrupt change characteristics (including abrupt change size and direction) between two adjacent scan points (i.e., the first scan point and the second scan point). The higher the similarity, the greater the conformity score.

[0134] Step S500: Obtain the fibrous region based on the boundaries of each part.

[0135] In this embodiment, the fibrotic region refers to an abnormal region in the cornea after phacoemulsification cataract surgery, characterized by specific structure and optical properties, formed due to tissue repair or pathological changes. Accurate identification of the fibrotic region is crucial for improving the accuracy of postoperative corneal thickness measurement, avoiding errors caused by light scattering and changes in refractive index, and providing a reliable basis for assessing corneal recovery. Specifically, step S500 involves acquiring the fibrotic region based on the boundaries of each part, including steps S510 to S550.

[0136] Step S510: Obtain the complete boundary based on the boundaries of each part.

[0137] In this embodiment, any reasonable method can be used to obtain the complete boundary from the individual partial boundaries. For example, step S510, which obtains the complete boundary based on the individual partial boundaries, includes steps S511 to S514.

[0138] Step S511: Based on the boundaries of each part, obtain the average thickness change value corresponding to each part boundary.

[0139] In this embodiment, the average thickness abrupt change is the average of the corresponding thickness differences (e.g., the first and second differences mentioned above) among the thickness abrupt change features of all scan points within the boundary region. It should be noted that calculating the average of multiple values ​​is a mature technique, and will not be elaborated upon here.

[0140] Step S512: Divide the boundary regions whose thickness mutation mean difference is less than or equal to the fifth preset value into the same group.

[0141] It is important to note that the mean thickness abrupt change reflects the overall intensity of the thickness abrupt change at that boundary. A smaller difference indicates that these partial boundaries are more likely to belong to the same fibrotic region (because the intensity of thickness abrupt changes within the same fibrotic region is consistent). This grouping method allows discrete partial boundaries belonging to the same fibrotic region to be clustered together, providing an integration target for subsequent expansion of head and tail scan points to form a closed, complete boundary, ultimately achieving accurate definition of the fibrotic region boundary.

[0142] In this embodiment, the implementer can adjust the fifth preset value according to the specific implementation environment. For example, the fifth preset value can be 0.02mm or 0.03mm. The larger the fifth preset value is set, the higher the tolerance for differences in thickness mutation features. More boundaries with similar but not completely consistent mutation features will be grouped together, which may lead to the incorrect fusion of the boundaries of different lesions and reduce the resolution of fibrotic area identification. Conversely, the smaller the fifth preset value is set, the stricter the grouping conditions will be. Only boundaries with highly consistent features will be grouped together. Although this improves the purity of identification, it may lead to the over-segmentation of the boundaries of the same lesion, making it impossible to form a complete closed loop.

[0143] Step S513: For any part of the boundary in each group, obtain its head scan point and tail scan point.

[0144] In this embodiment, the head scan point refers to the starting endpoint of a partial boundary arranged in the order of the lines connecting the scan points. For example, when a partial boundary is formed by connecting scan point i and the adjacent scan point i-1, if the order of the lines is from i-1 to i, then i-1 is the head scan point of that partial boundary. The tail scan point refers to the ending endpoint of a partial boundary arranged in the order of the lines connecting the scan points. Following the example above, scan point i is the tail scan point of that partial boundary.

[0145] Step S514: Based on the head scan point, select the adjacent scan point with the highest degree of correspondence with the head scan point in the second region, and add the adjacent scan point to the head of the partial boundary. Based on the tail scan point, select the adjacent scan point with the highest degree of correspondence with the tail scan point in the second region, and add the adjacent scan point to the tail of the partial boundary. Continue until the partial boundary forms a closed boundary, which is the complete boundary.

[0146] It should be noted that the calculation of the degree of agreement between the scan point (i.e., the head scan point or the tail scan point) and its adjacent scan points (i.e., the eight-neighbor scan points) can be referred to step S470, which will not be elaborated here.

[0147] Step S520: Based on the complete boundary, obtain the first mean and the second mean.

[0148] In this embodiment, the first mean is the average thickness of adjacent scan points on the outer periphery of the complete boundary. The second mean is the average thickness of all scan points outside the area enclosed by the complete boundary in the second region.

[0149] Step S530: Based on the complete boundary, obtain the third quantity and the fourth quantity.

[0150] In this embodiment, the third quantity is the total number of scan points contained in each partial boundary. The fourth quantity is the total number of scan points contained in the complete boundary.

[0151] Step S540: Based on the first mean, the second mean, the third quantity, and the fourth quantity, obtain the consistency value corresponding to the region surrounded by the complete boundary.

[0152] In this embodiment, the consistency value is negatively correlated with the absolute value of the difference between the first mean and the second mean, and positively correlated with the ratio of the third quantity to the fourth quantity. Specifically, in step S540, based on the first mean, the second mean, the third quantity, and the fourth quantity, the formula for calculating the consistency value corresponding to the region enclosed by the complete boundary is as follows:

[0153]

[0154] in, This indicates the degree of consistency corresponding to the region enclosed by the complete boundary; This represents the first mean; Indicates the second mean; Indicates the third quantity; 'a' represents the fourth quantity; 'a' represents the zero-prevention coefficient, which is any positive number close to 0. For example, the zero-prevention coefficient 'a' can be 0.01 or 0.001, etc.

[0155] In this embodiment, By quantifying the difference between the average thickness of adjacent scan points on the periphery of the complete boundary and the average thickness of the normal region outside the boundary, the smaller the difference, the greater the consistency value, reflecting that the transition between the outer boundary and the normal region is more reasonable. By calculating the proportion of the original boundary scan points in the complete boundary, the higher the proportion, the greater the consistency value, reflecting the stronger the support of the original boundary fragment for the complete boundary. Multiplying the two parts can quantify the degree to which the area surrounded by the complete boundary conforms to the characteristics of the fibrous region, providing a basis for accurately identifying the fibrous region.

[0156] Step S550: The region enclosed by the complete boundary with the largest consistency value is determined as the fibrotic region.

[0157] As mentioned earlier, the consistency score comprehensively measures the "reasonableness of the transition between the outer boundary and the normal area" and the "support of the original edge fragments to the boundary," ultimately achieving a quantitative judgment on whether the area surrounded by the complete boundary is a fibrous region. In other words, the region with the highest consistency score has a boundary that best matches the structural characteristics of a fibrous region, and can therefore be identified as a fibrous region, laying the foundation for subsequent precise adjustment of the refractive index and improvement of thickness detection accuracy.

[0158] Step S600: Based on the fibrotic region and the scanning density correction coefficient, adjust the scanning density and refractive index of the second region to obtain the final corneal thickness data.

[0159] In this embodiment, the calculation formula for adjusting the scan density of the second region based on the scan density correction coefficient can be as follows:

[0160] ;

[0161] in, This indicates the spacing between adjacent scan points after correction; This indicates the spacing between adjacent scan points before correction (which can be 0.3mm or 0.4mm, etc.). Indicates the scan density correction factor; This represents the normalization function, used to normalize the values ​​within the parentheses to the range [0, 1]. In this embodiment, the larger the scan density correction coefficient, the smaller the spacing between adjacent scan points after correction, i.e., the larger the scan density.

[0162] In this embodiment, the refractive index of the second region is adjusted based on the fibrous region, including steps S610 to S650.

[0163] Step S610: Based on the fibrous region, obtain the area value and the fourth thickness value.

[0164] In this embodiment, the area value is the area of ​​the fibrotic region. The fourth thickness value is the maximum thickness value corresponding to each scanning point in the fibrotic region.

[0165] Step S620: Based on the second region, obtain the fifth thickness value.

[0166] In this embodiment, the fifth thickness value is the average thickness of all scanning points outside the fibrotic region in the second region.

[0167] Step S630: Obtain the refractive index correction coefficient based on the area value, the fourth thickness value, and the fifth thickness value.

[0168] In this embodiment, the refractive index correction coefficient is positively correlated with the area value and also positively correlated with the difference between the fourth thickness value and the fifth thickness value. Specifically, in step S630, based on the area value, the fourth thickness value, and the fifth thickness value, the calculation formula for the refractive index correction coefficient is obtained as follows:

[0169] ;

[0170] in, This represents the refractive index correction factor; This represents the area value of the fibrotic region; This indicates the fourth thickness value; This represents the fifth thickness value. In this embodiment, the area of ​​the fibrous region... The larger the area, the wider the distribution of abnormal tissue, the more significant the overall impact of collagen disorder, and the larger the range of refractive index abnormalities. Therefore, the area value, as a positive parameter, directly reflects the "spatial extent" of fibrosis; that is, the larger the area, the stronger the need for refractive index correction. In this embodiment, Reflecting the structural differences between fibrotic and normal regions, if A higher value indicates a more pronounced local thickening or density anomaly in the fibrotic region, higher collagen cross-linking density, and a greater refractive index deviation. This parameter quantifies the "local intensity" of fibrosis, that is... The larger the value, the greater the correction needs to be.

[0171] Step S640: Based on the refractive index correction coefficient and the preset reference refractive index, obtain the target refractive index corresponding to the fibrous region.

[0172] Specifically, in step S640, based on the refractive index correction coefficient and the preset reference refractive index, the calculation formula for the target refractive index corresponding to the fibrous region is as follows:

[0173] ;

[0174] in, Indicates the target refractive index; This indicates the reference refractive index, which can be set according to requirements, typically 1.376. This represents the refractive index correction factor; This represents the normalization function, used to normalize the values ​​within the parentheses to the range [0, 1]. In this embodiment, a larger refractive index correction coefficient indicates a more severe degree of fibrosis in the fibrotic region, and consequently, a larger adjustment range in the refractive index of the fibrotic region, in order to compensate for the refractive index changes caused by disordered collagen arrangement and ensure the accuracy of corneal thickness measurement.

[0175] Step S650: Adjust the refractive index of the fibrous region to the target refractive index.

[0176] It is important to understand that adjusting the refractive index when measuring corneal thickness using anterior segment OCT is a well-established technique, and will not be elaborated upon here.

[0177] The embodiment of the corneal thickness measurement method after phacoemulsification cataract surgery based on anterior segment OCT proposed in this application divides the cornea into multiple first regions based on a region growing algorithm and initial corneal thickness data, achieving fine-grained corneal partitioning and avoiding the coarseness of overall uniform processing. By obtaining a scanning density correction coefficient positively correlated with the degree of corneal thickness non-uniformity in each first region, a second region with a scanning density correction coefficient greater than a first preset value is selected. The scanning is optimized for the second region to solve the problem that existing uniform scanning arrays cannot adapt to regions with thickness differences. By identifying adjacent scanning points with similar thickness abrupt change characteristics in the second region to form partial boundaries, the fibrotic region is determined, and the postoperative abnormal area is accurately located. Combining the fibrotic region and the scanning density correction coefficient, the scanning density and refractive index of the second region are adjusted to avoid the error of calculation using a uniform refractive index in existing technologies, ultimately achieving accurate measurement of corneal thickness and solving the technical problem that existing OCT detection cannot accurately measure the thickness of corneal regions.

[0178] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0179] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the methods, apparatuses, and devices described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0180] In the several embodiments provided in this application, it should be understood that the disclosed devices, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual couplings, direct couplings, or communication connections may be through some interfaces; indirect couplings or communication connections between devices or modules may be electrical, mechanical, or other forms.

[0181] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical modules; that is, they may be located in one place or distributed across multiple network modules. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0182] Furthermore, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can be stored in a computer-readable storage medium.

[0183] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product.

[0184] The computer program product includes one or more computer instructions. When the computer program is loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium may be any available medium that a computer can store or a data storage device such as a server or data center that integrates one or more available media. The available medium may be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., digital video optical disc), or a semiconductor medium (e.g., solid-state drive (SSD)).

[0185] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles of this application.

Claims

1. A method for detecting corneal thickness after phacoemulsification cataract surgery based on anterior segment OCT, characterized in that, include: Based on the region growing algorithm and initial corneal thickness data, the cornea is divided into multiple first regions; The initial corneal thickness data is acquired in advance; Obtain the scanning density correction coefficient corresponding to each first region; the scanning density correction coefficient is at least positively correlated with the degree of corneal thickness non-uniformity in the corresponding first region; Based on each first region, a second region is obtained; the second region is any first region whose scan density correction coefficient is greater than a first preset value. Based on the second region, multiple partial boundaries are obtained; the partial boundaries are the boundaries formed by connecting the first scan point and the second scan point; the first scan point and the second scan point are any two adjacent scan points in the second region, and the degree of similarity between the first scan point and the second scan point is greater than a second preset value; the degree of similarity is positively correlated with the similarity of the thickness abrupt change features between the first scan point and the second scan point. Based on the boundaries of each part, obtain the fibrous region; Based on the fibrotic region and the scanning density correction coefficient, the scanning density and refractive index of the second region are adjusted to obtain the final corneal thickness data. The adjustment of the refractive index of the second region based on the fibrous region includes: obtaining an area value and a fourth thickness value based on the fibrous region; the area value being the area of ​​the fibrous region; the fourth thickness value being the maximum thickness value corresponding to each scanning point in the fibrous region; obtaining a fifth thickness value based on the second region; the fifth thickness value being the average thickness of all scanning points outside the fibrous region in the second region; obtaining a refractive index correction coefficient based on the area value, the fourth thickness value, and the fifth thickness value; the refractive index correction coefficient being positively correlated with the area value and positively correlated with the difference between the fourth thickness value and the fifth thickness value; obtaining a target refractive index corresponding to the fibrous region based on the refractive index correction coefficient and a preset reference refractive index; and adjusting the refractive index of the fibrous region to the target refractive index.

2. The method for detecting corneal thickness after phacoemulsification cataract surgery based on anterior segment OCT according to claim 1, characterized in that, The initial corneal thickness data is acquired in advance, including: Based on the anterior segment OCT device, multiple scans are performed on different locations of the cornea according to a preset scanning matrix to obtain multiple first test results; Based on each first test result, multiple second test results are obtained; the second test result is the test result in which the signal strength of each first test result is greater than a third preset value. The initial corneal thickness data is obtained based on the average value of each second test result.

3. The method for detecting corneal thickness after phacoemulsification cataract surgery based on anterior segment OCT according to claim 1, characterized in that, The step of obtaining the scan density correction coefficients corresponding to each first region includes: Based on each first region, a third region is obtained; the third region is any region in each first region for which no corresponding scan density correction coefficient has been obtained; Based on the third region, a first thickness value and a second thickness value are obtained; the first thickness value is the maximum thickness value corresponding to each scanning point in the third region; the second thickness value is the minimum thickness value corresponding to each scanning point in the third region. Based on the first thickness value and the second thickness value, the scanning density correction coefficient corresponding to the third region is obtained.

4. The method for detecting corneal thickness after phacoemulsification cataract surgery based on anterior segment OCT according to claim 3, characterized in that, After obtaining the scanning density correction coefficient corresponding to the third region based on the first thickness value and the second thickness value, the method further includes: Based on the third region, multiple third thickness values ​​are obtained; the third thickness values ​​are the thickness values ​​of the corresponding scanning points in the third region. Based on each third thickness value, a first sequence is obtained; the third thickness values ​​in the first sequence are arranged in ascending order. Based on the first sequence, obtain the difference sequence; Based on the difference sequence, the first sequence is divided into multiple second sequences; Based on each second sequence, obtain a first quantity and a second quantity; the first quantity is the number of sequences with the most values ​​in each second sequence; the second quantity is the number of each second sequence. Based on the first quantity and the second quantity, an adjustment coefficient is obtained; the adjustment coefficient is used to correct the scan density correction coefficient corresponding to the third region.

5. The method for detecting corneal thickness after phacoemulsification cataract surgery based on anterior segment OCT according to claim 4, characterized in that, The step of dividing the first sequence into multiple second sequences based on the difference sequence includes: Based on the difference sequence, multiple abnormal sequence values ​​are obtained; the abnormal sequence value is any sequence value in the difference sequence that is greater than a fourth preset value. Based on each abnormal sequence value, obtain the minuend and subtrahend corresponding to each abnormal sequence value; Based on the minuend and the subtrahend, the first sequence is divided into multiple second sequences; wherein the subtrahend belongs to the first second sequence and the minuend belongs to the second sequence.

6. The method for detecting corneal thickness after phacoemulsification cataract surgery based on anterior segment OCT according to any one of claims 1 to 5, characterized in that, The method for obtaining the thickness abrupt change feature of the first scanning point includes: Based on the first scanning point, a third scanning point is obtained; the third scanning point is the scanning point with the largest difference in corneal thickness among the eight neighboring scanning points of the first scanning point. Based on the first scan point and the third scan point, a first difference and a first direction are obtained; the first difference is the difference in corneal thickness corresponding to the first scan point and the third scan point; the first direction is the direction from the first scan point to the third scan point. Based on the first difference and the first direction, the thickness abrupt change feature of the first scanning point is obtained.

7. The method for detecting corneal thickness after phacoemulsification cataract surgery based on anterior segment OCT according to claim 6, characterized in that, The method for obtaining the degree of agreement between the first scan point and the second scan point includes: Based on the second scan point, a second difference and a second direction are obtained; the second difference and the second direction are the thickness abrupt change features corresponding to the second scan point; Based on the first difference and the second difference, a third difference is obtained; the third difference is the absolute value of the difference between the first difference and the second difference. Based on the first direction and the second direction, a fourth difference is obtained; the fourth difference is the maximum rotation angle difference between the first direction and the second direction under different rotation angles of Euler angles. Based on the third difference and the fourth difference, the degree of agreement between the first scan point and the second scan point is obtained.

8. The method for detecting corneal thickness after phacoemulsification cataract surgery based on anterior segment OCT according to claim 7, characterized in that, The process of obtaining the fibrous region based on the boundaries of each part includes: Based on the boundaries of each part, obtain the complete boundary; Based on the complete boundary, a first mean and a second mean are obtained; the first mean is the average thickness of adjacent scan points on the outer periphery of the complete boundary; the second mean is the average thickness of all scan points outside the area enclosed by the complete boundary in the second region. Based on the complete boundary, a third quantity and a fourth quantity are obtained; the third quantity is the total number of scan points contained in each partial boundary; the fourth quantity is the total number of scan points contained in the complete boundary. Based on the first mean, the second mean, the third quantity, and the fourth quantity, a consistency value corresponding to the region enclosed by the complete boundary is obtained; the consistency value is negatively correlated with the absolute value of the difference between the first mean and the second mean, and positively correlated with the ratio of the third quantity to the fourth quantity; The region enclosed by the complete boundary with the highest consistency value is defined as the fibrotic region.

9. The method for detecting corneal thickness after phacoemulsification cataract surgery based on anterior segment OCT according to claim 8, characterized in that, The process of obtaining the complete boundary based on the partial boundaries includes: Based on the boundaries of each part, the mean thickness change value corresponding to each part boundary is obtained; the mean thickness change value is the average of the thickness difference values ​​in the thickness change features of all scanning points in that part boundary. The boundary regions where the mean difference of thickness mutation is less than or equal to the fifth preset value are divided into the same group; For any part of the boundary in each group, obtain its head scan point and tail scan point; Based on the head scan point, the adjacent scan point with the highest degree of correspondence with the head scan point is selected in the second region, and the adjacent scan point is added to the head of the partial boundary; based on the tail scan point, the adjacent scan point with the highest degree of correspondence with the tail scan point is selected in the second region, and the adjacent scan point is added to the tail of the partial boundary; until the partial boundary forms a closed boundary, the closed boundary is the complete boundary.

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