Centering balloon to improve esophageal photodynamic therapy

A cylindrical balloon was developed to improve delivery of circumferential light for photodynamic therapy (PDT) of esophageal carcinoma. The balloon consisted of a 36-mm-long clear cylindrical membrane and a central tube to hold a cylindrical diffuser in the center of the lumen. Three isotropic probes were placed on the outside of the balloon to allow measurement of delivered light dose to the esophageal mucosa. The balloon was tested in the normal esophagus of 8 dogs that were injected with 4.0 mg/kg of PHOTOFRINR. Endoscopy was performed 48 hours following the injection, and under endoscopic observation the balloon assembly was passed, fixed in place, and inflated. A 1-cm cylindrical diffuser was passed into the central tube and 150, 300, and 600 Joules/cm of 630 nm laser light was delivered at 25 cm, 15 cm, and 5 cm proximal to the gastroesophageal junction. One control dog was illuminated using the cylindrical diffuser alone at doses of 300 and 600 Joules/cm of diffuser. Complete circumferential tissue response was obtained when the balloon was used. Relatively uniform light intensities were measured around the lumen. In contrast, noncircumferential and unpredictable PDT responses were generated when the cylindrical diffuser was used without the balloon.