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Proceedings Paper

Flourescence analysis of ALA-induced Protoporphyrin IX in psoriatic plaque
Author(s): Mark R. Stringer; Dominic J. Robinson; P. Collins
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Paper Abstract

The success reported for the treatment of superficial skin carcinomas by photodynamic therapy (PDT), following topical application of 5-aminolaevulinic acid (ALA), has therapeutic implications for the treatment of other skin disorders. This presentation describes the accumulation of the photosensitizing agent protoporphyrin IX (PpIX) in areas of psoriatic plaque, by monitoring the fluorescence emission induced by low-intensity laser excitation at 488 nm. We present the results from 15 patients, with a total of 42 plaques. These results show that PpIX fluorescence increases in intensity within the 6 hour period following application of ALA, which implies there is a potential for PDT. The emission is localized to the area of ALA application and the effect of occlusion appears insignificant. Also, the rate of increase, and maximum intensity of fluorescence emission, is not directly related to the applied quantity of ALA. The variability of the fluorescence intensity is as great between plaques at different sites on the same patient as between different patients. We also present measurements of the depletion in intensity of fluorescence emission during PDT treatment, using white light, at an irradiance of 25 mW cm-2, that is a consequence of the molecular photo-oxidation of PpIX. The use of fluorescence measurements in predicting the therapeutic effect of treating plaque psoriasis by ALA-PDT is discussed.

Paper Details

Date Published: 31 January 1996
PDF: 8 pages
Proc. SPIE 2625, Photochemotherapy: Photodynamic Therapy and Other Modalities, (31 January 1996); doi: 10.1117/12.230971
Show Author Affiliations
Mark R. Stringer, Univ. of Leeds (United Kingdom)
Dominic J. Robinson, Univ. of Leeds (United Kingdom)
P. Collins, Leeds General Infirmary (United Kingdom)

Published in SPIE Proceedings Vol. 2625:
Photochemotherapy: Photodynamic Therapy and Other Modalities
Benjamin Ehrenberg; Giulio Jori; Johan Moan, Editor(s)

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