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In recent years, endoscopic optical coherence tomography (OCT) has garnered widespread attention for non-invasive advantages in achieving three-dimensional visualization of internal organ cavities. In early-stage lesions, microvascular alterations occur before morphological tissue changes. Therefore, utilizing endoscopic OCTA for the detection of superficial capillaries serves as an adjunctive method for early disease screening. About ten years ago, the advantages of high-speed and stable operation of distal motorized catheters enabled the realization of endoscopic OCTA. However, the internal micro-motors lead to a larger outer diameter of distal imaging catheters, which restricts their clinical applicability for monitoring diseases in narrow luminal structures. Consequently, proximal imaging catheters, with their smaller size, have found its wide application in the commercial arena. However, due to limitations in external motor speed and susceptibility to external vibrations, there were no reports of proximal imaging catheters achieving endoscopic OCTA for a long time. Recently, we proposed the MB-scan scheme to mitigate the impact of external motion artifacts and achieve endoscopic OCTA based on a proximal catheter. The Singular Value Decomposition (SVD) algorithm was employed to eliminate static tissue information and obtain en face OCTA images of the murine rectum. In this study, we proposed a fast endoscopic OCTA using proximal scanning catheter based on B-scan scheme and a customed image registration algorithm. Image registration based on the similarity between adjacent B-scan frames was utilized to reduce the impact of external motor vibrations and improve image quality. Based on the registered images at the same scanning position, the speckle variance (SVAR) algorithm was employed to calculate variation of OCT intensity signals. Finally, en face OCTA images were generated. Collecting data from the mouse rectum, endoscopic OCTA images were obtained from the registered data using the SVAR algorithm.
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