An optical coherence blood flow scanning imaging method

Abstract

The present invention relates to an optical coherence blood flow scanning imaging method, which belongs to the field of biomedical optical imaging technology. The method of the present invention comprises dividing the area to be scanned into a grid to obtain evenly distributed sampling points; grouping the sampling points, and performing n repeated scans on each group, wherein the time for each group to perform a scan is the same, and the time interval between two adjacent scans at each sampling point is consistent. The method of the present invention can ensure that the imaging system has the same spatial sampling interval in the entire sampling area. Moreover, the method of the present invention can flexibly set the sampling time interval, so that blood flow information under different flow rate conditions can be obtained. In other words, since the number of sampling points in each group can be flexibly selected, the time interval between two adjacent scans at the sampling point can also be customized, which facilitates the extraction of blood flow information under different flow rates.

Description

Technical Field

[0001] The invention relates to an optical coherence blood flow scanning imaging method, belonging to the technical field of biomedical optical imaging. Background Art

[0002] Optical coherence blood flow imaging is a non-invasive medical imaging technology that can identify blood flow information of the skin, iris, retina, and choroid with high resolution, and image the microvascular circulation of the skin, iris, retina, and choroid of living tissues. It has unique advantages in the management and follow-up of vascular changes in the skin, iris, retina, and choroid, as well as the detection of treatment effects. Its technical principle is mainly based on the concept that in static biological tissues (such as skin and eyeballs), the only moving structures are the blood cells flowing in the blood vessels. The traditional method repeatedly scans the same cross-section, and calculates the contrast between static and active structures to obtain blood flow signals, based on which two-dimensional and three-dimensional reconstruction of vascular structures is performed.

[0003] Currently, in most studies of optical coherence flow imaging, raster scanning, which scans the object line by line, is used. Consequently, the scanning range is restricted to a square or rectangular area, and the image is displayed in a square or rectangular format. However, this introduces two problems, as detailed below:

[0004] The first problem with traditional methods is that in optical coherence blood flow imaging systems, the single-mode fiber mode field, collimator spot, and optical lens output spot are all circular, so the imaging area with optimal resolution is usually also circular. In addition, the human eye's iris, pupil, and field of view are also circular. Therefore, using a square or rectangular scanning area cannot fully match the circular characteristic areas inherent in biological tissues (such as human eye tissue) (including the circular iris and circular photosensitive areas of the fundus) and the circular optimal resolution imaging area of ​​the imaging system. In other words, it results in low efficiency or imaging blind spots.

[0005] The following are common scanning formats:

[0006] When the scanning area (represented by the grid area) is not large enough, scanning the circular target area or the circular best resolution area (represented by the red area) will inevitably result in a scanning blind spot, and the image information of the blind spot area cannot be obtained. Figure 1 shown.

[0007] When the scanning area (represented by the grid area) is large enough, scanning the circular target area or the circular best resolution area (represented by the red area) will inevitably result in invalid scanning areas, such as Figure 2As shown by the arrows, since excessively tilted scanning light mostly fails to reach the sample, the image information in the ineffective scanning area is noise-like and meaningless, wasting scanning time and resulting in low efficiency. Furthermore, the same problem still exists for blood flow imaging of other circular tissues, such as the human iris.

[0008] Existing methods often stitch together multiple rectangular images to create a single image, but this requires complex software algorithms. Because biological tissue unconsciously moves due to heartbeat and blood pressure fluctuations, multiple images are unstable, requiring complex software algorithms for stitching. Furthermore, the stitched seams can produce unnatural blur and jumps. Furthermore, this method also has certain blind spots for circular target areas or circular optimal resolution areas.

[0009] Although circular scanning methods such as radial scanning already exist, the spatial density of the sampling points of these methods is uneven, that is, their spatial sampling intervals are not equal, resulting in oversampling in some areas and undersampling in other areas. This makes it impossible to effectively utilize the spatial resolution of the optical system and is therefore undesirable.

[0010] The second problem with traditional methods: In order to simplify the scheme, traditional scanning methods often have only two options for the time interval for repeated scanning at the same location of biological tissue, namely the time of an A-scan or the time of a cross-sectional scan (B-scan). It is well known that the time interval between repeated scans is related to the flow velocity of the blood flow information obtained. When the time interval is relatively short, only blood flow information with a relatively fast flow velocity can be obtained. When the time interval is relatively long, the content obtained includes blood flow information with high and low flow velocities. In this way, because traditional scanning methods often cannot flexibly change this time interval, the flow velocity conditions of the blood flow information obtained can only be fixed, making it difficult to extract more flow velocity information. Summary of the Invention

[0011] The technical problem solved by the present invention is: to overcome the deficiencies of the prior art and propose an optical coherence blood flow scanning imaging method to achieve high-efficiency, blind-angle-free, and self-defined scanning time interval imaging, thereby avoiding blind angles and invalid scanning.

[0012] The technical solution of the present invention is:

[0013] An optical coherence blood flow scanning imaging method, the method comprising the steps of:

[0014] The first step is to divide the area to be scanned into grids to obtain evenly distributed sampling points;

[0015] In the second step, the sampling points obtained in the first step are grouped according to the order of scanning, namely the first group, the second group, ... the Nth group;

[0016] The third step is to repeat the scan n times for the first group, then repeat the scan n times for the second group, and so on, and repeat the scan n times for the Nth group. The time taken to perform one scan for each group is the same, and the time interval between two adjacent scans at each sampling point is consistent (that is, the time interval between two adjacent scans at each sampling point in the same group is consistent, and the time interval between two adjacent scans at each sampling point in different groups is also consistent). During the scanning, the return light at the scanning position can be obtained;

[0017] In the fourth step, the return light at the scanning position obtained in the third step interferes with the return light from the reference arm in the interferometer of the optical coherence blood flow imaging system. The interference signal is then collected by the acquisition device and sent to the computer for processing. The computer sequentially obtains n structural information at each sampling point in the scanning area based on the obtained interference signal.

[0018] In the fifth step, an optical coherence blood flow imaging algorithm (such as one based on correlation analysis or principal component analysis) is used to extract the blood flow information corresponding to each sampling point in the scan area from the n structural information at each sampling point in the scan area obtained in the fourth step. Finally, the extracted blood flow information is arranged according to the spatial position of each sampling point in the scan area to obtain reconstructed blood flow information of the biological tissue, completing optical coherence blood flow scanning imaging.

[0019] In the second step, the number of sampling points in each group may be consistent or inconsistent when grouping. When the number of sampling points in each group is inconsistent, the time interval between two adjacent scans at each sampling point is made consistent by increasing the waiting time during repeated scanning.

[0020] The scanning scheme is as follows: the scanning area is divided into equally spaced grids to obtain M evenly distributed grid nodes, each grid node represents a scanning sampling point, and the M sampling points are grouped into N groups, namely the first group, the second group, ... the Nth group. The sampling points of the first group are scanned for the first time according to the scanning order (such as S-shaped), and then scanned for the second time, and so on, to complete n scans of the first group. Among them, the interval time between two adjacent scans at each sampling point is expressed as T0 = m*t0 + τ0, m is the number of sampling points in the group, t0 is the single scan time at each sampling point, and τ0 is the scanning beam reset time. In order to make the scanning time interval T0 of each group of sampling points the same, the scanning beam reset time is extended accordingly if the number of sampling points in the group is small; for example, the number of sampling points in each of the first N-1 groups is m, and the number of sampling points in the last group is m′. In order to make the scanning time of each group the same, the scanning beam reset time of the last group is extended to (mm′)t0+τ0;

[0021] The M sampling points can be divided into one group, that is, N=1, and the single scanning time of this group (that is, the time interval between two adjacent samplings of each sampling point) is T0=M*t0+τ0;

[0022] Alternatively, each sampling point can be considered as a group, i.e., N = M. When N = M, simply repeat the acquisition n times at each sampling point and then move to the next sampling point. The single scan time of each group (i.e., the sampling time interval of each sampling point) is the single scan time at each sampling point, i.e., T0 = t0. In this case, there is no need to consider the scanning beam reset time.

[0023] In summary, the lower limit of the sampling time interval for any sampling point is T0=t0, and the upper limit is T0=M*t0+τ0. If τ0 is increased, the upper limit can be an arbitrarily large time interval. Therefore, the selection of the sampling time interval is very flexible. Since the time interval of repeated scanning is related to the flow velocity of the acquired blood flow information, it is possible to flexibly extract more flow velocity information while obtaining the blood flow distribution in the biological sample.

[0024] The above steps complete the repeated scanning of the sampling points in the area to be scanned. The return light signal of the scanned position enters the interferometer of the optical coherence blood flow imaging system and interferes with the return light of the reference arm. The interference signal is then collected by the acquisition device, and the data is sent to the computer for processing to obtain the structural information of the sample at depth. Then, based on the optical coherence blood flow imaging algorithm (such as an algorithm based on correlation analysis or an algorithm based on principal component analysis), the corresponding blood flow information is extracted from the structural information obtained by n scans at each position of the biological sample. Finally, according to the spatial position of each group of sampling points on the biological tissue, the blood flow information is arranged in the image to obtain the reconstructed blood flow information of the biological tissue.

[0025] Beneficial effects

[0026] 1. Traditional methods cannot fully match the circular features inherent in imaging systems and biological tissues (such as the human eye), including the circular iris and the circular photosensitive area of ​​the fundus, resulting in low efficiency or imaging blind spots. The method of the present invention can avoid these problems and provide a highly efficient imaging method with no blind spots.

[0027] 2. Although traditional circular scanning methods such as radial scanning already exist, the spatial sampling intervals of traditional circular scanning methods are uneven, resulting in oversampling in some areas and undersampling in others, which fails to effectively utilize the spatial resolution of the optical system. The method of the present invention ensures that the spatial sampling interval is uniform across the entire sampling area.

[0028] 3. Compared with traditional methods, the method of the present invention can flexibly set the sampling time interval, so it can obtain blood flow information under different flow rate conditions.

[0029] 4. Compared with the traditional method, in the method of the present invention, since the number of sampling points in each group can be flexibly selected, the time interval between two adjacent scans at each sampling point can also be customized, which facilitates the extraction of blood flow information at different flow rates.

[0030] 5. The present invention relates to an optical coherence blood flow scanning imaging method, belonging to the field of biomedical optical imaging technology. The method comprises dividing the area to be scanned into a grid to obtain evenly distributed sampling points; grouping the sampling points and performing n repeated scans on each group, with each group performing a scan with the same duration and the time interval between two adjacent scans at each sampling point being consistent; a sample arm captures return light from the area to be scanned and returns it to an interferometer, where this return light interferes with the return light from the reference arm; an acquisition device then collects the interference signal, which is then sent to a computer for processing. The computer uses the interference signal to obtain structural information at each sampling point and extracts the corresponding blood flow information. The method ensures that the imaging system maintains consistent spatial sampling intervals across the entire sampling area. Furthermore, the sampling interval can be flexibly set, enabling the acquisition of blood flow information under varying flow rates. In other words, since the number of sampling points in each group can be flexibly selected, the time interval between two adjacent scans at a sampling point can also be customized, facilitating the extraction of blood flow information under varying flow rates. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is an optical coherence blood flow imaging scanning method with blind spots;

[0032] Figure 2 It is an inefficient optical coherence blood flow imaging scanning method;

[0033] Figure 3 This is a schematic diagram of group repeated scanning according to the present invention. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0035] Example

[0036] In conventional optical coherence blood flow imaging systems, light from a light source enters an interferometer and is split into two paths: one entering the reference arm and the other entering the sample arm. The light from the sample arm passes through a two-dimensional deflection system and a lens assembly, where it is focused onto the surface of the sample to be imaged (such as the anterior chamber or fundus). The specific location of the beam is determined by the two-dimensional deflection system and the focal length of the lens assembly.

[0037] In the sample arm, the two-dimensional deflection system and lens group are used to converge the sample light to a specific position on the sample and collect the backscattered light there, thus completing the sampling at this location. The two-dimensional deflection system determines the deflection angle of the sample light. The lens group is used to focus the deflected light onto the sample, which determines the spot size on the sample, that is, the lateral resolution. The two-dimensional deflection system is controlled to perform segmented repeated scanning of the area to be scanned in the sample. The return light obtained by the scanning interferes with the return light from the reference arm in the interferometer. The interference signal is then collected by the acquisition device and the data is sent to the computer for processing. The computer processes the collected interference signal data to sequentially obtain the structural information at the depth of these scanning points. Then, based on the optical coherence blood flow imaging algorithm (such as an algorithm based on correlation analysis or an algorithm based on principal component analysis), the corresponding blood flow information is extracted from the structural information obtained from multiple scans at each sampling point of the sample.

[0038] In this embodiment, the area to be scanned is selected as a circle. The specific scheme for segmented repeated scanning of the circular area is as follows: Based on the rectangular coordinate system, the circular area to be scanned is divided into grids, such as Figure 3 As shown. In this circular area, there are 101 grid nodes, which represent the sampling points of the scan, and are represented by × in the figure. Each grid node will be scanned n times, and the sampling time interval of these n scans is T0. According to the S-shaped scanning order, the points scanned successively are grouped in sequence, and each group has m points. In this example, m=18 is taken as a demonstration. Figure 3 In the figure, each group of points is represented by an × of a different color. The serial number of each group is written near the starting point of the group, and there are a total of 6 groups. The 6th group has less than 18 points, only 11 points, and is also considered a group. The two-dimensional deflection system is controlled so that the light beam repeatedly scans the points in each group n times in groups. For example: scan from the first point of the 1st group to the last point, then return to the first point of the 1st group to scan to the last point, and repeat this process n times. The number of points in the 6th group is 11. To ensure that the scanning time of each group is the same, after scanning the last point of the 6th group, the scanning light beam is made to wait for 7 times the single-point scanning time before performing the subsequent scan.

[0039] Blood flow is a fluid. Compared with the relatively static tissue around it, the interference spectrum generated by the light reflected from it and returned to the interferometer and the reference arm will change more significantly over time. By scanning multiple times to obtain optical interference signals at different times at the same position, multiple structural information at equal time intervals can be obtained. According to the analysis of multiple structural information obtained at the same position, if the structure at a certain depth changes significantly over time, it is considered that there is blood flow at that depth. Here, the value of m determines the time interval between two acquisitions at each sampling point. Since the selection of m is very flexible, the sampling time interval has a very large selection range. Because the flow velocity of the obtained blood flow information is related to the sampling time interval, this scheme can not only obtain the blood flow distribution in biological samples, but also flexibly extract blood flow information at more flow rates, which is not available in traditional methods. In addition, this method is also applicable to applications based on optical coherence detection to obtain other fluid information (such as lymphatic vessel distribution, etc.).

[0040] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An optical coherence blood flow scanning imaging method, characterized in that The steps of the method include: The first step is to divide the area to be scanned into grids to obtain evenly distributed sampling points; In the second step, the sampling points obtained in the first step are grouped according to the order of scanning, namely the first group, the second group, ... the Nth group; The third step is to repeat the scanning of the first group n times, then repeat the scanning of the second group n times, and so on, and repeat the scanning of the Nth group n times. The time for each group to perform a scan is the same, and the time interval between two adjacent scans at each sampling point is consistent. While scanning, the return light at the scanning position is obtained; In the fourth step, the return light at the scanning position obtained in the third step interferes with the return light from the reference arm in the interferometer of the optical coherence blood flow scanning imaging system. The interference signal is then collected by the acquisition device and sent to the computer for processing. The computer sequentially obtains n structural information at each sampling point in the scanning area based on the obtained interference signal. In the fifth step, the blood flow information corresponding to each sampling point is extracted from the n structural information at each sampling point in the scanning area obtained in the fourth step, and the extracted blood flow information is then arranged to obtain the reconstructed blood flow information of the biological tissue, thereby completing the optical coherence blood flow scanning imaging.

2. The optical coherence blood flow scanning imaging method according to claim 1, characterized in that: In the third step, the time interval between two adjacent scans at each sampling point in the same group is consistent, and the time interval between two adjacent scans at each sampling point in different groups is also consistent.

3. The optical coherence blood flow scanning imaging method according to claim 1 or 2, characterized in that: In the fifth step, blood flow information corresponding to each sampling point is extracted based on an optical coherence blood flow imaging algorithm.

4. The optical coherence blood flow scanning imaging method according to claim 3, characterized in that: The optical coherence blood flow imaging algorithm is an algorithm based on correlation analysis or an algorithm based on principal component analysis.

5. The optical coherence blood flow scanning imaging method according to claim 1, characterized in that: In the fifth step, the extracted blood flow information is arranged according to the spatial position of each group of sampling points in the scanning area.

6. The optical coherence blood flow scanning imaging method according to claim 1, characterized in that: In the second step, the number of sampling points in each group is consistent when grouping. If the remaining points are insufficient, they are also grouped together. When scanning the last group of sampling points, the waiting time between repeated scans is increased to make the time interval between two adjacent scans at each sampling point consistent.

7. The optical coherence blood flow scanning imaging method according to claim 1, characterized in that: In the second step, the number of sampling points in each group is inconsistent during grouping, and the time interval between two adjacent scans at each sampling point is made consistent by increasing the waiting time between repeated scans.

8. The optical coherence blood flow scanning imaging method according to claim 1, characterized in that: The scanning area is divided into equally spaced grids to obtain M evenly distributed grid nodes, each grid node representing a scanning sampling point. The M sampling points are grouped into N groups, namely the first group, the second group, ... the Nth group. The sampling points of the first group are scanned for the first time in the scanning order, and then scanned for the second time, and so on, to complete n scans of the first group; wherein, the interval time between two adjacent scans at each sampling point is expressed as T0 = m*t0 + τ0, m is the number of sampling points in the group, t0 is the single scanning time at each sampling point, and τ0 is the scanning beam reset time; in order to make the scanning time interval T0 of each group of sampling points the same, the scanning beam reset time is correspondingly extended if the number of sampling points in the group is small.

9. The optical coherence blood flow scanning imaging method according to claim 8, characterized in that: The M sampling points are divided into one group, that is, N=1, and the time interval between two adjacent sampling points of each sampling point in this group is T0=M*t0+τ0.

10. The optical coherence blood flow scanning imaging method according to claim 8, characterized in that: Each sampling point is regarded as a group, that is, N=M. When N=M, it is only necessary to repeat the acquisition n times at each sampling point and then move to the next sampling point. In this case, the sampling time interval at each sampling point is the single scanning time, that is, T0=t0, and there is no need to consider the scanning beam reset time.

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