Endoscopic OCTA imaging method and imaging system based on pause stepwise rotation scanning

Abstract

The application discloses an endoscopic OCTA imaging method and imaging system based on a pause stepping rotation scanning, wherein according to the imaging spot size of a catheter and the scanning inner wall circumference, the maximum step length of a motor is determined; the timing of a stepping motor driving signal is determined through the pause collection line number, the collection time, the preset duty ratio, the scanning frequency of a light source and the step angle of the motor; the stepping motor is driven to rotate the catheter by a preset angle according to the rotation timing, and the catheter is paused at the scanning position; when the catheter is paused, the OCTA optical imaging module is triggered to collect multiple Aline data; and the multiple Aline data are integrated into an endoscopic OCTA image. The Aline scanning is stable, and the influence of the to-be-measured tissue vibration on the imaging is eliminated by adopting the stepping and pausing dense Aline scanning mode and through the timing control so that no data is collected in the stepping rotation process.

Description

Technical Field

[0001] This invention relates to the field of optical coherence tomography imaging technology, and in particular to an endoscopic OCTA imaging method and system based on pause-stepping rotational scanning. Background Technology

[0002] Optical coherence tomography (OCT) is currently recognized as a high-resolution imaging technology in the field of medical imaging. It is characterized by high resolution, non-contact, and non-destructive features, and is often referred to as "optical biopsy." OCTA (OCT Angiography) can distinguish blood vessels from other tissue structures and extract image information of blood vessels within tissues, and has already played a role in ophthalmic treatment and the treatment of port-wine stains. Endoscopic OCTA imaging is a relatively new technology that can be used for microvascular imaging within blood vessels, the digestive tract, and other tracts, becoming a new clinical diagnostic method.

[0003] Traditional OCTA imaging involves repeated B-scan scans to compare changing components between adjacent B-scans, filtering out invariant background tissue and extracting flowing blood signals. However, this method requires the imaging probe to remain relatively stable, limiting its application primarily to ophthalmology and dermatology. Newer imaging methods based on dense A-line scanning compare changes between adjacent A-lines. Because the time interval between A-lines is much smaller than the time interval between B-scans, it can be used for vascular imaging in stable tissues, as well as tissues with low amplitude and speed of vibration, such as the digestive and respiratory tracts. However, current dense A-line scanning methods involve continuous catheter rotation, resulting in physical offsets between adjacent A-lines. This leads to poor imaging results for tissues with high amplitude and frequency of vibration, such as the microvessels on the surface of a beating heart, due to significant background noise interference. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide an endoscopic OCTA imaging method and system based on pause-stepping rotational scanning. It adopts a pause-stepping scanning method, performing OCTA imaging scanning during pauses and changing the data acquisition position during rotation, thus creating a new data acquisition method and completely solving the problems of large jitter amplitude and noise interference during imaging.

[0005] To achieve the above objectives, the present invention provides an endoscopic OCTA imaging method based on pause-step rotational scanning, comprising the following steps:

[0006] The maximum step size of the motor stepping (i.e. the maximum angle of one rotation) is determined based on the size of the imaging spot of the catheter and the circumference of the inner wall.

[0007] Based on the number of pause acquisition lines, acquisition time, preset duty cycle, light source scanning frequency, and step angle of the stepper motor, the advance timing of the stepper motor drive signal is set through formula calculation.

[0008] The stepper motor drives the guide tube to rotate into a preset angle according to the rotation sequence, and stops when it reaches the scanning position;

[0009] When the catheter stops, the OCTA optical imaging module is triggered to acquire multiple A-line data at the location where the catheter stops.

[0010] Multiple Aline data were integrated into an endoscopic OCTA image.

[0011] More preferably, the step of determining the maximum step size of the motor stepper based on the size of the imaging spot of the catheter and the circumference of the scanned inner wall; and setting the advance timing of the stepper motor drive signal based on the number of pause acquisition lines, acquisition time, preset duty cycle, scanning frequency of the light source, and step angle of the motor; includes the following steps:

[0012] S101. Based on the scanned inner wall circumference l and the minor axis length b of the elliptical spot emitted parallel to the reference position by the catheter, calculate the minimum number of steps n required for the catheter to rotate one revolution, where n>l / b.

[0013] S102. Based on the minimum number of steps n required for the catheter to rotate one revolution, calculate the maximum step length of the catheter stepping scan, θ=360° / n;

[0014] S103, according to the scanning frequency f of the light source sweep And the number of Aline samples n during a pause A Determine the duration t2 of data acquisition when the motor stops;

[0015] S104. Based on the duration t2 of the pause acquisition and the duty cycle D of the enable signal, calculate the frequency f of the stepper motor enable signal. en ;

[0016] S105. Convert the step size of the catheter stepping scan into a multiple of the motor step angle γ, and determine the frequency f of the motor drive signal. d The step size of the catheter stepping scan must meet the requirements of S102.

[0017] Duration of data acquisition when the motor stops Calculate using the following formula

[0018] .

[0019] More preferably, the frequency f of the enable signal en The following formula is used for calculation:

[0020]

[0021] Where: D is the duty cycle; t1 is the motor running time; t2 is the motor stopping time.

[0022] More preferably, the drive signal frequency f of the motor d The following formula is used for calculation:

[0023]

[0024] Where D is the duty cycle; θ is the step size of the catheter stepping scan; and γ is the step angle of the stepper motor.

[0025] The present invention also provides an endoscopic OCTA imaging system based on pause step-rotation scanning, including an optical driver, an OCTA optical imaging module, a data acquisition module, an imaging catheter, a controller, and an image processing unit;

[0026] The optical driver includes a stepper motor, a pullback motor, and an optical connector. The stepper motor is used to drive the imaging catheter to rotate into the blood vessel at a preset angle. The pullback motor is used to drive the imaging catheter to pull back for scanning. The optical connector is used to connect the optical driver to the imaging catheter.

[0027] The controller includes a timing control unit, which is used to set the rotation timing of the enable signal and the stepper motor drive signal; the enable signal is used to trigger the stepper motor to stop and trigger the OCTA optical imaging module to perform OCTA scanning; the stepper motor drive signal is used to control the stepper motor to drive the imaging guide tube to rotate in a preset angle and switch the scanning position.

[0028] The OCTA optical imaging module is used for optical coherence imaging;

[0029] The data acquisition module is used to collect multiple Aline data at the location where the catheter stops when it stops.

[0030] The image processing unit is used to integrate multiple Aline data into an endoscopic OCTA image.

[0031] More preferably, the timing control unit includes a parameter preset module and a timing calculation module; the parameter preset module includes:

[0032] Set the inner wall circumference l of the scan, the minor axis length b of the elliptical spot emitted parallel to the reference position of the catheter, and calculate the minimum number of steps n required for the catheter to rotate one revolution and the maximum step size of the catheter step scan, θ=360° / n;

[0033] The timing calculation module is used to convert the step size of the catheter stepping scan into the step angle of the motor. The multiple of the value determines the enable signal for the motor drive; based on the enable signal and its duty cycle, the advance timing of the stepper motor drive signal is calculated.

[0034] More preferably, when the timing calculation module calculates the precession timing of the stepper motor drive signal, it includes: obtaining the scanning frequency f of the OCTA scanning light source. sweep and the number of Aline samples n collected at each step position A The acquisition duration t2 is calculated; based on the acquisition time and the duty cycle of the enable signal, the frequency f of the enable signal is calculated. en ; Calculate the motor drive signal frequency f based on the enable signal frequency. d .

[0035] More preferably, the frequency f of the enable signal en The following formula is used for calculation:

[0036]

[0037] Where: D is the duty cycle; t1 is the motor running time; t2 is the motor stopping time.

[0038] More preferably, the drive signal frequency f of the motor d The following formula is used for calculation:

[0039]

[0040] Where D is the duty cycle; θ is the step size of the catheter step scan; This is the step angle of the stepper motor.

[0041] The endoscopic OCTA imaging method and system disclosed in this application, based on pause-step rotational scanning, has at least the following advantages compared to the prior art:

[0042] By employing a pause-step control method to control catheter rotation, the catheter does not rotate during data acquisition, maintaining relative stability in A-line scanning. This reduces the impact of tissue background noise during OCTA imaging of moving tissues and improves the quality of microvascular imaging. Attached Figure Description

[0043] Figure 1 This is a schematic flowchart of the endoscopic OCTA imaging method based on pause-step rotational scanning according to the present invention.

[0044] Figure 2 This is a schematic diagram of the step-rotation scanning of the endoscopic catheter of the present invention.

[0045] Figure 3 This is a waveform diagram of the stepper motor drive signal of the present invention.

[0046] Figure 4 This is a timing diagram of the K-clock signal and Trigger signal output by the swept frequency light source of the present invention.

[0047] Figure 5 The waveform of the Trigger signal after synchronization with the motor is shown in this invention.

[0048] Figure 6 This is an organizational chart.

[0049] Figure 7 This is a diagram of blood vessel structures.

[0050] Figure 8 A diagram of vascular structures with the tissue background removed.

[0051] Figure 9 This is a three-dimensional projection image of blood vessels. Detailed Implementation

[0052] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0053] In vascular imaging based on dense A-line scanning, background noise interference occurs when imaging tissue vessels with large amplitude and high frequency of jitter due to physical deviations between adjacent A-lines. The method disclosed in this invention uses a stepper motor to drive the catheter to rotate, employing a step-pause dense A-line scanning method. That is, the catheter does not rotate continuously for a full revolution, but is controlled by the motor to rotate a certain angle each time, stopping at a predetermined position. Data is acquired during the pause, collecting several A-line data points at the same position. Timing control prevents data acquisition during the step-rotation process, thus achieving stable A-line scanning.

[0054] Example 1: Specific scheme as follows Figure 1 As shown, an embodiment of the present invention provides an endoscopic OCTA imaging method based on pause-step rotation scanning, which includes the following steps:

[0055] S1. Determine the maximum step size of the motor stepper (i.e., the maximum angle of one rotation) based on the size of the imaging spot of the catheter and the circumference of the inner wall. Based on the number of pause acquisition lines, acquisition time, preset duty cycle, scanning frequency of the light source, and step angle of the stepper motor, calculate and set the rotation timing of the stepper motor drive signal using the formula.

[0056] S2. The stepper motor drives the guide tube to rotate into a preset angle according to the rotation sequence, and stops when it reaches the scanning position;

[0057] S3. When the catheter stops, the OCTA optical imaging module is triggered to collect multiple Aline data at the stopping position of the catheter.

[0058] S4. Integrate multiple Aline data into an endoscopic OCTA image.

[0059] S1 in this embodiment specifically includes:

[0060] S101. Based on the scanned inner wall circumference l and the minor axis length b of the elliptical spot emitted parallel to the reference position by the catheter, calculate the minimum number of steps n required for the catheter to rotate one revolution, where n>l / b.

[0061] S102. Based on the minimum number of steps n required for the catheter to rotate one revolution, calculate the maximum step length of the catheter stepping scan, θ=360° / n;

[0062] S103, according to the scanning frequency f of the light source sweep And the number of Aline samples n during a pause A Determine the duration t2 of the pause in data collection;

[0063] S104. Based on the duration t2 of the pause acquisition and the duty cycle D of the enable signal, calculate the frequency f of the stepper motor enable signal. en ;

[0064] S105. Convert the step size of the catheter stepping scan into a multiple of the motor step angle γ, and determine the frequency f of the motor drive signal. d The step size of the catheter stepping scan must meet the requirements of S102.

[0065] like Figure 2 As shown, to ensure the entire inner wall is scanned, n > l / b, where l represents the circumference of the inner wall and b represents the minor axis of the elliptical spot emitted from the conduit. At a depth of 2 mm from the center of the conduit, b = 0.8 mm, and l = 2 * 2 * π ≈ 13 mm, therefore n > 16, θ < 22.5°. To avoid image distortion and for ease of calculation and control, n should be chosen to be slightly larger, for example, n = 100.

[0066] Further steps are needed to determine the step size (angle value) of the catheter stepping scan. The step size of the rotation stepping is θ = 360° / n, where n represents the number of steps required for one rotation. When n = 100, θ = 3.6°.

[0067] Furthermore, in S104, when calculating the rotation timing of the stepper motor drive signal based on the signal frequency of the motor drive and the duty cycle D of the enable signal, the timing control includes two aspects: stepper rotary motor drive and data acquisition synchronization, which are interrelated.

[0068] First, let's discuss the timing of the motor enable signal. The step angle γ of a stepper motor is typically 0.9°, 1.8°, or 3.6°. A step length θ = 3.6° requires 4 signal cycles, 2 signal cycles, and 1 signal cycle, respectively. A smaller step angle results in higher motor control accuracy. This method can use any of these step angles. The stepper motor drive signal is generally a square wave, triggered by either the rising or falling edge. The default is continuous stepping. To achieve the effect of waiting for data acquisition after stepping, an enable signal needs to be connected. The enable signal is active high, meaning the motor drives the guide tube to rotate stepping. During the low-level period of the enable signal, the drive signal does not trigger stepping, i.e., it pauses and waits for data acquisition. The duty cycle of the high level is D. Let the motor movement time be t1 and the motor pause time be t2, then...

[0069]

[0070] The formula for calculating the acquisition time t2 is as follows:

[0071]

[0072] Among them, f sweep This indicates the scanning frequency of the frequency-sweeping light source, which is also the frequency of the trigger signal for data acquisition. Existing technologies offer different types ranging from 50kHz to 800kHz. Taking 100kHz as an example, f... sweep =100K=100000. n A This represents the number of A-lines collected at each step position. Since time and frequency are reciprocals, the frequency f of the motor enable signal can be obtained. en :

[0073]

[0074] For ease of use, D is set to 50%, meaning the motor's running time t1 and its stopping time t2 are equal. If n A =50, then f en =1000.

[0075] The formula for calculating the motor drive signal frequency is:

[0076]

[0077] If a motor with a step angle of 3.6° is used, then θ = The motor movement requires one signal cycle. After the stepper rotates, it needs to wait for one signal cycle for data scanning. At this time, f d =2000;

[0078] If a motor with a step angle of 1.8° is used, then θ = 2. Then the motor runs for two cycles and waits for two cycles, at which point fd =4000. Similarly, we can obtain the f of a motor with a step angle of 0.9°. d =8000.

[0079] Taking γ=3.6° as an example, the waveforms of the drive signal and enable signal of the stepper motor triggered by the rising edge are as follows: Figure 3 As shown.

[0080] Secondly, the timing of the motor enable signal needs to be synchronized with the timing of the data acquisition. The timing of the data acquisition comes from the trigger signal and the K-clock signal of the light source. The acquisition is triggered by the rising edge of the trigger signal, and its timing diagram is as follows. Figure 4 As shown in the image.

[0081] Finally, the motor enable signal needs to be synchronized with the trigger signal for data acquisition from the scanning light source. The purpose is to prevent data acquisition during motor movement. The motor enable signal is inverted, causing the high and low levels to flip, and then multiplied with the data acquisition trigger signal to obtain the synchronized acquisition trigger signal, such as... Figure 5 As shown.

[0082] Finally, multiple Aline data points need to be integrated into an endoscopic OCTA image. The integration calculation process is as follows:

[0083] 1. One rotation of the catheter constitutes one Bscan. The number of steps required for one rotation is n, and the number of A-line samples acquired in each step is n. A Each Aline contains L points. The data from a Bscan is denoted as matrix B, which is L*(n*n) A A two-dimensional matrix;

[0084] 2. Each A-line of the Bscan is shaped using a Hanning window, and then subjected to a Fourier transform along the L-dimensional plane to obtain the spectral information Bf of the OCTA structural imaging. The calculation formula is as follows:

[0085]

[0086] Where Bf represents the L-dimensional spectral information, which is a complex matrix; B represents the raw data collected by Bscan; and Bwin is the Hanning window matrix. Indicates Fourier transform;

[0087] By performing structural initialization calculations on the spectral data Bf, the structural image St of the tissue under test can be obtained. The calculation formula is as follows:

[0088] St=255*[20*ln(1+|Bf|)-RgSt(1)] / [RgSt(2)-RgSt(1)]

[0089] Where |Bf| represents modulo the complex number Bf, RgSt represents the normalization parameter of the tissue structure diagram, RgSt(1) represents the lower limit, RgSt(2) represents the upper limit, and 255* represents converting the normalized result into a grayscale image. The result of the tissue structure diagram St is as follows: Figure 6 As shown in the figure, the result is after compression, and the same applies below.

[0090] 3. Extract blood flow information from the spectral information of structural imaging. The extraction method is to compare the changes between adjacent Alines to obtain the blood flow signal. The calculation process is to first take the modulus of Bf to obtain the intensity information of the structural imaging spectrum, and then along (n*n A The spectrum information between Alines is obtained by performing a Fourier transform along the (n*n) dimension, then filtered by a BwinT filter window to extract the high-frequency components of the spectrum, and then further processed along (n*n) dimensions. A The inverse Fourier transform of the blood flow signal is performed in the 3D dimension to filter out background noise, yielding the structural imaging spectral information Bflow of the blood flow signal. The calculation formula is as follows:

[0091]

[0092] in Indicates along (n*n) A Fourier transform of 1 / 2 dimension Indicates along (n*n) A The inverse Fourier transform of dimension 1 is performed, where |Bf| represents the modulus of Bf, and BwinT is the filtering window. Its construction method is as follows: low-frequency components are 0, high-frequency components are 1, and a half-Hanning window is used for smooth transition. The data lengths for low and high frequencies are determined based on the effective information of the spectral signal. Considering that the result of the Fourier transform is symmetrical along the midpoint axis, this filtering window is also copied symmetrically.

[0093] 4. Next, the structural information Sf of blood flow is recovered from the spectral information of the blood flow signal. The calculation formula is as follows:

[0094] Sf=255*[20*ln(1+|Bflow|)-RgFl(1)] / [RgFl(2)-RgFl(1)]

[0095] Where |Bflow| represents modulo the complex number Bflow, RgFl represents the normalization parameter of the vascular structure image, RgFl(1) represents the lower limit, RgFl(2) represents the upper limit, and 255* represents converting the normalized result into a grayscale image. The result of the vascular structure image Sf is as follows: Figure 7 As shown.

[0096] 5. The next step is to reduce background noise. From Figure 7 and Figure 6The comparison shows that although the filtering in step 3 did not completely remove the tissue background noise, it greatly enhanced the blood flow signal and weakened the background tissue signal. Next, we only need to subtract the influence of the tissue structure diagram St from the vascular structure diagram Sf to obtain the blood flow signal F1 with the tissue background removed. The calculation formula is as follows:

[0097] F1=255*[(Sf-Coef*St)-RgNo(1)] / [RgNo(2)-RgNo(1)];

[0098] Where Coef represents the attenuation coefficient, RgNo represents the normalization parameter, RgNo(1) represents the lower limit, and RgNo(2) represents the upper limit. Blood flow signals with the tissue background removed, such as... Figure 8 As shown.

[0099] 6. Through the above calculations, the blood flow signal contained in one B-scan can be obtained. By using a pull-back motor to drive the catheter back for rotational scanning, multiple B-scan blood flow signals can be obtained. Superimposing these B-scan blood flow signals yields a three-dimensional blood flow map. Projecting this three-dimensional blood flow map produces a planar vascular distribution map, completing OCTA microvascular imaging, such as... Figure 9 As shown.

[0100] Example 2

[0101] The present invention also provides an endoscopic OCTA imaging system based on pause step-rotation scanning for implementing the above method, including an optical driver, an OCTA optical imaging module, a data acquisition module, an imaging catheter, a controller, and an image processing unit.

[0102] The optical driver includes a stepper motor, a pullback motor, and an optical connector. The stepper motor is used to drive the imaging catheter to rotate into the blood vessel at a preset angle. The pullback motor is used to drive the imaging catheter to pull back for scanning. The optical connector is used to connect the optical driver to the imaging catheter.

[0103] The controller includes a timing control unit, which is used to set the rotation timing of the enable signal and the stepper motor drive signal; the enable signal is used to trigger the stepper motor to stop and trigger the OCTA optical imaging module to perform OCTA scanning; the stepper motor drive signal is used to control the stepper motor to drive the imaging guide tube to rotate in a preset angle and switch the scanning position.

[0104] The OCTA optical imaging module is used for optical interferometric imaging;

[0105] The data acquisition module is used to collect multiple Aline data at the location where the catheter stops when it stops.

[0106] The image processing unit is used to integrate multiple Aline data into an endoscopic OCTA image.

[0107] Furthermore, the timing control unit includes a parameter preset module and a timing calculation module; used to implement steps S101-S105 in the above method embodiments, the parameter preset module includes:

[0108] Set the inner wall circumference l of the scan, the minor axis length b of the elliptical spot emitted parallel to the reference position of the catheter, and calculate the minimum number of steps n required for the catheter to rotate one revolution and the maximum step size of the catheter step scan, θ=360° / n;

[0109] The timing calculation module is used to convert the step size of the catheter stepping scan into a multiple of the step angle γ of the motor, and determine the enable signal of the motor drive; based on the enable signal of the motor drive and the duty cycle of the enable signal, the rotation timing of the stepper motor drive signal is calculated.

[0110] When the timing calculation module calculates the precession timing of the stepper motor drive signal, it includes:

[0111] Obtain the scanning frequency f of the OCTA optical imaging module sweep and the number of Aline samples n collected at each step position A The acquisition duration t2 is calculated; based on the acquisition time and the duty cycle of the enable signal, the frequency f of the enable signal is calculated. en ;

[0112] Calculate the motor drive signal frequency f based on the enable signal frequency. d .

[0113] The frequency f of the enable signal en The following formula is used for calculation:

[0114]

[0115] Where: D is the duty cycle; t1 is the motor running time; t2 is the motor stopping time.

[0116] The drive signal frequency f of the motor d The following formula is used for calculation:

[0117]

[0118] Where D is the duty cycle; θ is the step size of the catheter step scan; This is the step angle of the stepper motor.

[0119] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An endoscopic OCTA imaging method based on pause-step rotational scanning, characterized in that, Includes the following steps: The maximum step size of the motor stepper is determined based on the imaging spot size of the catheter and the scanning circumference of the inner wall; the advance timing of the stepper motor drive signal is set based on the number of pause acquisition lines, acquisition time, preset duty cycle, scanning frequency of the light source, and step angle of the stepper motor; including: S101. Based on the inner wall circumference and the minor axis length of the elliptical light spot emitted parallel to the reference position, calculate the minimum number of steps required for the catheter to rotate one revolution. S102. Calculate the maximum step length of catheter stepping scan based on the minimum number of steps required for the catheter to rotate one revolution; S103, According to the scanning frequency f of the light source sweep And the number of Aline samples n during a pause A Determine the duration t2 of data acquisition when the motor stops; S104. Based on the duration of the pause acquisition and the duty cycle D of the enable signal, calculate the frequency f of the stepper motor enable signal. en ; S105. Convert the step size of the catheter stepping scan into a multiple of the motor step angle γ, and determine the frequency f of the motor drive signal. d The step size of the catheter stepping scan must meet the requirements of S102; The stepper motor drives the guide tube to rotate into a preset angle according to the rotation sequence, and stops when it reaches the scanning position; When the catheter stops, the OCTA optical imaging module is triggered to acquire multiple A-line data at the location where the catheter stops. Multiple Aline data were integrated into an endoscopic OCTA image.

2. The endoscopic OCTA imaging method based on pause-step rotational scanning according to claim 1, characterized in that, The process involves determining the maximum step size of the motor stepper based on the size of the imaging spot in the catheter and the circumference of the scanned inner wall; and setting the advance timing of the stepper motor drive signal based on the number of pause acquisition lines, acquisition time, preset duty cycle, scanning frequency of the light source, and step angle of the motor. This includes the following steps: In S101, the minimum number of steps n required for the catheter to rotate one revolution is n>l / b, where l is the circumference of the inner wall being scanned and b is the minor axis length of the elliptical spot emitted parallel to the reference position by the catheter. In S102, the maximum step size of the catheter stepping scan is θ = 360° / n, where n is the minimum number of steps required for the catheter to rotate once.

3. The endoscopic OCTA imaging method based on pause-step rotational scanning according to claim 2, characterized in that, Duration of data acquisition when the motor stops The following formula is used for calculation: 。 4. The endoscopic OCTA imaging method based on pause-step rotational scanning according to claim 3, characterized in that, The frequency f of the enable signal en The following formula is used for calculation: Where: D is the duty cycle; t1 is the motor running time; t2 is the motor stopping time.

5. The endoscopic OCTA imaging method based on pause-step rotational scanning according to claim 3, characterized in that, The drive signal frequency f of the motor d The following formula is used for calculation: Where D is the duty cycle; θ is the step size of the catheter stepping scan angle; This is the step angle of the stepper motor.

6. An endoscopic OCTA imaging system based on pause-step rotational scanning, characterized in that, It includes an optical driver, an OCTA optical imaging module, a data acquisition module, an imaging conduit, a controller, and an image processing unit; The optical driver includes a stepper motor, a pullback motor, and an optical connector. The stepper motor is used to drive the imaging catheter to rotate into the blood vessel at a preset angle. The pullback motor is used to drive the imaging catheter to pull back for scanning. The optical connector is used to connect the optical driver to the imaging catheter. The controller includes a timing control unit, which is used to set the advance timing of the enable signal and the stepper motor drive signal; the enable signal is used to trigger the stepper motor to stop and trigger the OCTA optical imaging module to perform OCTA scanning. The stepper motor drive signal is used to control the stepper motor to rotate the imaging catheter forward by a preset angle and switch the scanning position; The OCTA optical imaging module is used for optical coherence imaging; The data acquisition module is used to collect multiple Aline data at the location where the catheter stops when it stops. The image processing unit is used to integrate multiple Aline data into an endoscopic OCTA image.

7. The endoscopic OCTA imaging system based on pause-stepping rotational scanning according to claim 6, characterized in that, The timing control unit includes a parameter preset module and a timing calculation module; The parameter preset module includes: Set the inner wall circumference l, the minor axis length b of the elliptical spot emitted parallel to the reference position by the catheter, and calculate the minimum number of steps n required for the catheter to rotate one revolution and the maximum step size θ of the catheter stepping scan, θ=360° / n; The timing calculation module is used to convert the step size of the catheter stepping scan into a multiple of the step angle γ of the motor, and determine the timing of the enable signal of the motor drive; based on the enable signal of the motor drive and the duty cycle of the enable signal, the rotation timing of the stepper motor drive signal is calculated.

8. The endoscopic OCTA imaging system based on pause-stepping rotational scanning according to claim 7, characterized in that, When the timing calculation module calculates the precession timing of the stepper motor drive signal, it includes: Obtain the scanning frequency f of the light source used in the OCTA optical imaging module sweep and the number of Aline samples n collected at each step position A The acquisition duration is calculated; based on the acquisition time and the duty cycle of the enable signal, the frequency f of the enable signal is calculated. en ; Calculate the motor drive signal frequency f based on the enable signal frequency. d .

9. The endoscopic OCTA imaging system based on pause-step rotational scanning according to claim 8, characterized in that, The frequency f of the enable signal en The following formula is used for calculation: Where: D is the duty cycle; t1 is the motor running time; t2 is the motor stopping time.

10. The endoscopic OCTA imaging system based on pause-stepping rotational scanning according to claim 8, characterized in that, The drive signal frequency f of the motor d The following formula is used for calculation: Where D is the duty cycle; θ is the step size of the catheter step scan; This is the step angle of the stepper motor.

Images