Doppler optical coherence tomography monitoring of microvascular tissue response during photodynamic therapy in an animal model of Barrett's esophagus

Background: Doppler optical coherence tomography (DOCT) is an imaging modality that allows assessment of the microvascular response during photodynamic therapy (PDT) and may be a powerful tool for treatment monitoring/optimization in conditions such as Barrett's esophagus (BE). Objective: To assess the technical feasibility of catheter-based intraluminal DOCT for monitoring the microvascular response during endoluminal PDT in an animal model of BE. Design: Thirteen female Sprague-Dawley rats underwent esophagojejunostomy to induce enteroesophageal reflux for 35 to 42 weeks and the formation of Barrett's mucosa. Of these, 9 received PDT by using the photosensitizer Photoftin (12.5 mg/kg intravenous), followed by 635-nm intraluminal light irradiation 24 hours after drug administration. The remaining 4 surgical rats under-went light irradiation without Photofrin (controls). Another group of 5 normal rats, without esophagojejunostomy also received PDT DOCT imaging of the esophagus by using a catheter-based probe (1.3-mm diameter) was performed before, during, and after light irradiation in all rats. Results: Distinct microstructural differences between normal squamous esophagus, BE, and the transition zone between the 2 tissues were observed on DOCT images. Similar submucosal microcirculatory effects (47%-73% vascular shutdown) were observed during PDT of normal esophagus and surgically induced BE. Controls displayed no significant microvascular changes. Conclusions: No apparent difference was observed in the PDT-induced vascular response between normal rat esophagus and the BE rat model. Real-time monitoring of PDT-induced vascular changes by DOCT may be beneficial in optimizing PDT dosimetry in patients undergoing this therapy for BE and other conditions.