Propylene glycol as a contrasting agent for optical coherence tomography to image gastrointestinal tissues

Background and Objective: Optical coherence tomography (OCT) is a recently developed imaging technique that has the potential to advance the early diagnosis of diseases in the human gastrointestinal (GI) tract. However, the high scattering nature of GI tissue limits its imaging depth and contrast. For more effective diagnosis using OCT, a concurrent improvement of imaging depth and contrast is, therefore, needed. In this work, we investigate the administration of chemical agents to the tissue as a means of improving the capability of OCT imaging of clinically relevant microstructures of the GI tract. Study Design/Materials and Methods: Normal human GI tissues, including stomach and oesophagus were obtained from patients in hospital, and were imaged with OCT within 0.5-2 hours of removal. Immediately after the first imaging of the specimens with OCT, about 0.5 ml of 80% propylene glycol solution was applied onto the tissue surface and the tissue allowed to absorb the chemical compounds for 20 minutes. Another image was then taken at the same position. The specimens were then embedded and stained in preparation for histologic evaluation. Co-registration of the images obtained using OCT before and after the topical application of the propylene glycol solution, and standard histopathologic processing provided basis for comparison. Results: More detailed micro-structures, including the basal layer position and the cellular composition of the mucosal layer of GI tract tissues were observed after the topical application of propylene glycol solution, while these structures were not resolvable in the conventional OCT images. Conclusions: Propylene glycol could be used as a contrasting agent for OCT imaging of human GI tract tissues, allowing an increased capability of OCT for rapid clinical diagnosis in vivo. Lasers Surg. Med. 30:201-208, 2002. (C) 2002 Wiley-Liss, Inc.