title: In situ light dosimetry during photodynamic therapy of Barrett's esophagus with 5-aminolevulinic acid.
abstract: OBJECTIVE
  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.
  
  
  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(-2). 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.
  
  
  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.
authors.affiliation: Photodynamic Therapy and Optical Spectroscopy Program, Erasmus MC, Rotterdam, The Netherlands.
authors.forename: Robert L P
authors.initials: RL
authors.lastname: van Veen
authors.forename: Maurice C G
authors.initials: MC
authors.lastname: Aalders
authors.forename: Kasper L
authors.initials: KL
authors.lastname: Pasma
authors.forename: Peter D
authors.initials: PD
authors.lastname: Siersema
authors.forename: Jelle
authors.initials: J
authors.lastname: Haringsma
authors.forename: Wim
authors.initials: W
authors.lastname: van de Vrie
authors.forename: Edward E E
authors.initials: EE
authors.lastname: Gabeler
authors.forename: Dominic J
authors.initials: DJ
authors.lastname: Robinson
authors.forename: Henricus J C M
authors.initials: HJ
authors.lastname: Sterenborg
mesh_terms: D000622:Aminolevulinic Acid / Q000627:therapeutic use*; D001471:Barrett Esophagus / Q000188:drug therapy*; D004947:Esophagus / Q000528:radiation effects; D006801:Humans; D008027:Light; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D010865:Pilot Projects; D011446:Prospective Studies; D011874:Radiometry; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D013997:Time Factors
chemical_list: D017319:Photosensitizing Agents; D000622:Aminolevulinic Acid