Variables in photodynamic therapy for Barrett's esophagus
2009
Photodynamic therapy with porfimer sodium (PS) is a treatment option for high grade dysplasia associated with Barrett's
esophagus. This study sought to investigate the optical properties of Barrett's dysplasia that may be useful in light
dosimetry planning and to determine the effect of PS on tissue absorption and scattering. Fiber optic reflectance spectra
were collected before and 48 hours after administration of 2 mg/kg PS. Mucosal biopsies were collected at the same
locations. According to Monte Carlo analysis, the fiber optic probe sampled only the mucosal layer. A mathematical fit
of the reflectance spectra was performed as a function of blood volume fraction, oxygen saturation and scattering. The
average calculated blood volume was 100% higher in Barrett's tissue than normal esophageal tissue. The average
scattering slope from 620 to 750 nm was 26% higher for Barrett's dysplasia than normal esophageal tissue, indicating an
increase in the size of scattering particles. The difference in the scattering amplitude was not statistically significant,
suggesting no significant increase in the number of scattering particles. PS tissue content was determined with extraction
methods. Changes in the scattering slope due to PS sensitization were observed; however they were not proportional to
the extracted PS concentration.
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