Correction of non-uniform rotational distortion in proximally controlled endoscopic OCT using microfluidic phantom

In endoscopic OCT systems, the imbalance in torque load during rotational scanning will lead to non-uniform rotation of the distal probe, inevitably resulting in Non-Uniform Rotational Distortion (NURD) in the images. NURD can cause image translation and stretching or compression issues at arbitrary positions in OCT images, leading to misalignment of image information and impeding the implementation of endoscopic OCTA. In high-speed distal scanning OCT system, the instantaneous rotational speed of the micro-motor's metal struts was measured for OCT data resampling, enabling NURD correction, and OCTA was successfully realized. In proximal scanning, NURD is a more serious problem due to torque transmission over longer distances, resulting in asymmetric friction at different positions. In recent years, local block matching (LBM) and improved Features from Accelerated Segment Test (FAST) algorithms were used to solve NURD in B-scan images in proximal controlling OCT system. Cross-sectional OCTA was successfully implemented. In this paper, Global registration and A-line registration were used to correct NURD in continuous rotation and retraction of proximally controlled OCT imaging. Global registration was used to correct extensive NURD in B-scan images and A-line registration was applied for fine correction of minor NURD. Results from microfluidic data collected under the same position and retraction conditions demonstrate the effectiveness of NURD correction, and en face OCTA imaging was realized for the first time in a proximally controlled endoscopic OCT.