Comparison between pulsed and continuous-wave lasers for photodynamic therapy

摘要

A study was conducted in the normal canine esophagus to compare continuous wave (argon-pumped dye-laser) and pulsed (KTP/532-pumped dye-laser) laser light for photodynamic therapy with PHOTOFRIN$+R$/. 48 hours post injection, 630 nm laser light was delivered using a 24 mm diameter cylindrical esophageal PDT balloon positioned at either distal or proximal esophagus. A 1.0 cm cylindrical diffuser placed in the center of the balloon delivered 300 J/cm of light at an intensity of 400 mW/cm. Three dogs received continuous wave (CW) light proximally and pulsed light distally. Four dogs received CW light distally and pulsed light proximally. The light dose delivered to the esophageal mucosa was measured using three isotropic probes placed on the balloon wall. Similar mucosal light doses were verified for sites receiving pulsed or CW laser light. Two days after PDT, the severity of the esophageal lesions were evaluated endoscopically, grossly and histologically. While some response variability was observed among different animals, endoscopic examination of the lesions revealed comparable injury from CW and pulsed light in each subject. Based on the gross and histological examination of the lesions, the CW and pulsed laser-induced injuries could not be distinguished.