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Fluorescence contrast and threshold limit: implications for photodynamic diagnosis of basal cell carcinoma

Journal article
Authors Marica B Ericson
Carin Sandberg
F. Gudmundson
A. Rosén
Olle Larkö
Ann-Marie Wennberg
Published in Journal of Photochemistry and Photobiology. B: Biology
Volume 69
Issue 2
Pages 121-7
ISSN 1011-1344
Publication year 2003
Published at Institute of Selected Clinical Sciences, Department of Dermatology and Venereology
Department of Physics (GU)
Pages 121-7
Language en
Subject categories Dermatology and Venereal Diseases, Molecular physics


This study was designed to evaluate what application time of delta-5-aminolaevulinic acid (ALA) results in highest contrast between tumour and normal skin, in the interval 1-4 h, when using photodynamic diagnosis (PDD) of basal cell carcinomas (BCC) located on the face. Moreover, a value of the demarcation limit has been derived based on the fluorescence variation in normal skin adjacent to the tumour. Forty patients were included in the study, randomly allocated to four different groups with varying ALA application time in the range 1-4 h. The contrast, defined as the ratio between the fluorescence intensity in ALA-treated tumour tissue and normal skin, was calculated for each patient, and the mean values in each group were evaluated as a function of ALA application time. In addition, the fluorescence intensity variation in ALA-treated normal skin adjacent to the tumour was assessed. The results from this study show a peak of the mean contrast values after 3 h ALA application, but due to large interpatient variation, the mean contrast did not differ significantly in the interval 2-4 h. After 2 h ALA application, the fluorescence intensity variation in the normal ALA-treated skin was found to be at a maximum, which suggests that 2 h ALA application is not preferable when using PDD. Based on data of the fluorescence variation in ALA-treated normal skin after 3 and 4 h ALA application, a tolerance interval was calculated implying that values above 1.4 times the mean normal fluorescence indicate an abnormal condition. This tolerance limit agrees well with results obtained in a former study.

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