Centering balloon to improve esophageal photodynamic therapy

Abstract

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.

In situ light dosimetry during photodynamic therapy of Barrett's esophagus with 5‐aminolevulinic acid

“…This may explain the difference in fluence rate build-up factor between the two diffuser lengths. Panjehpour et al [19,20] also measured the fluence (rate) in a normal canine esophagus model using isotropic detectors. They found relatively small variations of approximately AE 12% between the (n ¼ 8) different animals.…”

Using white light during photodynamic therapy: visualization only or treatment?

“…Among them, the concentration of photosensitizer inside the tissue at the time of light application, the presence of oxygen and the light irradiance itself play a major role. When considering the treatment of the esophagus, several studies have already considered the difficulty in obtaining an optimal irradiance [9,10]. The comparison of PDT results in the esophagus between groups following protocols that are more or less optimized and with reasonably well-adapted light distributing devices clearly indicates that optimal devices (such as balloon) lead to much improved therapy [11].…”

Endobronchial Phototoxicity of WST 09 (Tookad®), a New Fast-Acting Photosensitizer for Photodynamic Therapy: Preclinical Study in the Pig¶

“…The delivery of light energy was performed with a cylindrical diffuser inserted into a specially designed balloon catheter similar to previously designed models for esophageal PDT (31–33). This has the advantage of improved centering of the diffuser, leading to a more homogenous light delivery.…”

“…This has the advantage of improved centering of the diffuser, leading to a more homogenous light delivery. In addition, the exact surface area treated is known, so that fluence can be calculated on a square centimeter basis instead of solely on the basis of the length of the diffuser, allowing more precise light dosimetry (31).…”