A fiber balloon catheter for uniform light delivery in intraductal photodynamic therapy of bile duct tumors

Background: Intraductal photodynamic therapy (PDT) is a promising minimally invasive treatment for bile duct tumors, but clinical efficacy is limited by uneven intraductal light distribution and light dose attenuation induced by intraluminal blood and bile. Objective: To develop an optical transmission device for intraductal PDT of bile duct tumors and optimize the light irradiation strategy. Methods: The power density distribution was analyzed by COMSOL simulation, and laser attenuation by blood and bile was quantified using an integrating sphere power meter. A fiber–balloon catheter was constructed and evaluated in two pigs that received hematoporphyrin derivative (2 mg/kg) 48 h preoperatively. Under cholangiographic guidance, the device was inserted via enterotomy, and laser irradiation was delivered at 100 mW/cm² for 1200 s. Histopathology was assessed at 3 days post-PDT. Results: Blood and bile caused 32.5 % to 45.8 % laser power attenuation. In a 1-cm-diameter duct, eccentric fiber positioning produced 2- to 3-fold wall power density variations. The balloon catheter maintained stable central fiber positioning, expelled intraluminal fluids, and caused no adverse events. Histopathology revealed circumferential, uniform bile duct epithelial necrosis at 3 days post-PDT. Conclusions: The cylindrical fiber balloon catheter is safe and feasible, and it can effectively improve the uniformity of light irradiation during intraductal PDT for bile duct tumors.