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Proceedings Paper

Establishment of treatment parameters for ALA-PDT of plaque psoriasis
Author(s): Mark R. Stringer; Dominic J. Robinson; P. Collins
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Paper Abstract

We report an investigation into the use of photodynamic therapy (PDT), following topically applied 5-aminolaevulinic acid (ALA), as a treatment for plaque psoriasis. Treatment was performed 4 hours post-ALA, using white light doses of 2 - 16 J cm-2 delivered at 10 - 40 mW cm-2. The fluorescence emission of protoporphyrin IX was used as an indicator of the relative concentration of photosensitizer within each plaque before, during, and after therapy. Results show that the rate of sensitizer photo- oxidation is proportional to both pre-treatment fluorescence intensity and surface irradiance, consistent with a rate- equation analysis. A correlation of fluorescence measurements with clinical response of plaques indicates that the effectiveness of PDT is dominated by the level of PpIX at the onset of treatment, and is much less dependent upon light dose. Using these findings we have established a PDT treatment protocol that involves the delivery of 8 J cm-2 of white light, at a rate of 15 mW cm-2. The possibility of ALA-PDT being established as the therapy of choice is discussed.

Paper Details

Date Published: 4 December 1996
PDF: 5 pages
Proc. SPIE 2924, Photochemotherapy: Photodynamic Therapy and Other Modalities II, (4 December 1996); doi: 10.1117/12.260785
Show Author Affiliations
Mark R. Stringer, Research School of Medicine/Univ. of Leeds (United Kingdom)
Dominic J. Robinson, Research School of Medicine/Univ. of Leeds (United Kingdom)
P. Collins, Leeds General Infirmary (United Kingdom)


Published in SPIE Proceedings Vol. 2924:
Photochemotherapy: Photodynamic Therapy and Other Modalities II
Stanley B. Brown; Benjamin Ehrenberg; Johan Moan, Editor(s)

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