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

Abstract

Background and Objectives: Previous studies with PhotoDynamic Therapy (PDT) in bladder and bronchi have shown that due to scattering and reflection, the actually delivered fluence rate on the surface in a hollow organ can be significantly higher than expected. In this pilot study, we investigated the differences between the primary calculated and the actual measured fluence rate during PDT of Barrett's Esophagus (BE) using 23 independent clinical measurements in 15 patients. Study Design/Materials and Methods: A KTP-dye module laser at 630 nm was used as light source. Light delivery was performed using a cylindrical light diffuser inserted in the center of an inflatable transparent balloon with a length corresponding to the length of the Barrett's epithelium. The total light output power of the cylindrical diffuser was calibrated using an integrating sphere to deliver a primary fluence rate of 100 mW cm À2 . Two fiber-optic pseudo sphere isotropic detectors were placed on the balloon and were used to measure fluence rate at the surface of the esophageal wall during PDT. Results and Conclusions: The actual fluence rate measured was 1.5-3.9 times higher than the primary fluence rate for 630 nm. In general, the fluence rate amplification factor decreased with increasing redness of the tissue and was less for shorter diffusers. Fluence rate variations in time were observed which coincided with patients coughing, movement, and esophageal spasms. These factors combined with inter patient variability of the fluence rate measured appears to justify the routine application of this technique in PDT of BE.

Pilot Study on Light Dosimetry Variables for Photodynamic Therapy of Barrett's Esophagus with High-Grade Dysplasia

“…PDT light delivery for the esophagus is unique because the esophagus is a hollow organ in which reflected light enhances the light fluence that is delivered directly from the fiber optic light source. Panjehpour et al (10) and van Veen et al (11) measured the actual light fluence at the mucosal surface and found that it was 1.5 to 3.9 times higher than expected. Mackenzie et al (12) reported that esophageal 5-aminolaevulinic acid-PDT treatment success was correlated to the administered PDT light dose.…”

A Systematic Review and Meta-Analysis of the Treatment for Barrett’s Esophagus

“…There was no statistically significant difference between APC and MPEC in terms of the efficacy to achieve endoscopic and histological reversal of BE. Although the number of available randomized controlled therapeutic trials is limited, these conclusions are supported by a large amount of experimental and clinical data and with the underlying pathophysiology of BE [6][7][8][9][10][11][12][13][14][15].…”

“…Several new techniques have been reported to produce successful ablation of BE, including multipolar electrocoagulation (MPEC) [6,7], argon plasma coagulation (APC) [8,9], photodynamic therapy (PDT) [10][11][12], and endoscopic mucosal resection [11,12]. The results of a number of studies suggest that these techniques are of a similar efficacy and that major side-effects are unlikely [13][14][15].…”

Performance of a dedicated light delivery and dosimetry device for photodynamic therapy of nasopharyngeal carcinoma: Phantom and volunteer experiments

“…This fluence rate build-up varies with the geometrical shape and tissue optical properties (scattering and absorption), and has been reported to be as high as a factor of 7.5 in the bladder [8]. In another study, we have measured fluence rate variations during PDT of Barrett's oesophagus [9]. The results showed a dramatic variation between patients, with fluence rate build-up factors ranging from 1.5 up to 4.…”