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Journal of Biomedical Optics • Open Access

Dual-channel red/blue fluorescence dosimetry with broadband reflectance spectroscopic correction measures protoporphyrin IX production during photodynamic therapy of actinic keratosis

Paper Abstract

Dosimetry for aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) photodynamic therapy of actinic keratosis was examined with an optimized fluorescence dosimeter to measure PpIX during treatment. While insufficient PpIX generation may be an indicator of incomplete response, there exists no standardized method to quantitate PpIX production at depths in the skin during clinical treatments. In this study, a spectrometer-based point probe dosimeter system was used to sample PpIX fluorescence from superficial (blue wavelength excitation) and deeper (red wavelength excitation) tissue layers. Broadband white light spectroscopy (WLS) was used to monitor aspects of vascular physiology and inform a correction of fluorescence for the background optical properties. Measurements in tissue phantoms showed accurate recovery of blood volume fraction and reduced scattering coefficient from WLS, and a linear response of PpIX fluorescence versus concentration down to 1.95 and 250 nM for blue and red excitations, respectively. A pilot clinical study of 19 patients receiving 1-h ALA incubation before treatment showed high intrinsic variance in PpIX fluorescence with a standard deviation/mean ratio of <0.9 . PpIX fluorescence was significantly higher in patients reporting higher pain levels on a visual analog scale. These pilot data suggest that patient-specific PpIX quantitation may predict outcome response.

Paper Details

Date Published: 4 July 2014
PDF: 15 pages
J. Biomed. Opt. 19(7) 075002 doi: 10.1117/1.JBO.19.7.075002
Published in: Journal of Biomedical Optics Volume 19, Issue 7
Show Author Affiliations
Stephen C. Kanick, Thayer School of Engineering at Dartmouth (United States)
Scott C. Davis, Thayer School of Engineering at Dartmouth (United States)
Yan Zhao, Thayer School of Engineering at Dartmouth (United States)
Tayyaba Hasan, Wellman Ctr. for Photomedicine (United States)
Edward V. Maytin, Cleveland Clinic Lerner Research Institute (United States)
Brian W. Pogue, Thayer School of Engineering at Dartmouth (United States)
Wellman Ctr. for Photomedicine (United States)
Darmouth-Hitchcok Medical Ctr. (United States)
M. Shane Chapman, Dartmouth Hitchcock Medical Ctr. (United States)


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