Endomicroscopic optical coherence tomography for cellular resolution imaging of gastrointestinal tracts.

Our ability to detect neoplastic changes in gastrointestinal (GI) tracts is limited by the lack of an endomicroscopic imaging tool that provides cellular-level structural details of GI mucosa over a large tissue area. In this article, we report a fiber-optic-based micro-optical coherence tomography (OCT) system and demonstrate its capability to acquire cellular-level details of GI tissue through circumferential scanning. The system achieves an axial resolution of 2.48m in air and a transverse resolution of 4.8m with a depth-of-focus (DOF) of similar to 150m. To mitigate the issue of limited DOF, we used a rigid sheath to maintain a circular lumen and center the distal-end optics. The sensitivity is tested to be 98.8dB with an illumination power of 15.6mW on the sample. With fresh swine colon tissues imaged ex vivo, detailed structures such as crypt lumens and goblet cells can be clearly resolved, demonstrating that this fiber-optic OCT system is capable of visualizing cellular-level morphological features. We also demonstrate that time-lapsed frame averaging and imaging speckle reduction are essential for clearly visualizing cellular-level details. Further development of a clinically viable OCT endomicroscope is likely to improve the diagnostic outcome of GI cancers.