Endoscopic OCTA in continuous rotation and retraction scheme using a proximal scanning catheter.

Endoscopic optical coherence tomography (OCT) is widely used in the detection of morphological alterations in luminal organs, which provides high-resolution, three-dimensional (3D) images of internal tissues. In most cases, lesions are revealed early by microvascular pathological changes in cavity tissues. There is a significant demand for the performance of endoscopic OCT angiography (OCTA) to visualize the superficial capillaries. Proximal catheters have attracted widespread attention due to the advantages of small size and low cost. However, in comparison with the OCT system using distal catheters, low rotation speed and poor stability of the proximal scanning OCT prolonged its absence of endoscopic OCTA in common commercial and lab systems. In this paper, endoscopic OCTA was realized in the proximal scanning endoscopic OCT system by calculating decorrelation between adjacent B-scan images in the continuous rotation and retraction scheme. A precision registration algorithm was proposed to guarantee the quality of the OCTA image. The feasibility of the endoscopic OCTA was validated using a microfluidic phantom. In vivo studies were performed in the rat rectum, visualizing the intricate microvascular architecture, specifically within the submucosal capillaries. To the best of our knowledge, the first implementation of endoscopic OCTA was achieved under a continuous spiral B-scan rotation scheme in a proximally controlled OCT system, facilitating visualization of blood flow within narrow lumen tissues.