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

摘要

This study was designed to evaluate what application time of delta-5-aminolaevulinic acid (ALA) results inhighest contrast between tumour an normal skin in the interval 1-4 h when usi photodynamic diagnosis (PDD) of based cell carcionomas (BCC) located on the face Moreover a alue of ht emarcatin limit aha ben derivaed based on the fluoresecence variationin normal skin adjacent to the tumour Forty patients were included in the study randomly sllocated to four different groups with varying ALA appliati time in the rang 1-4 h The contrast defined as the ratio between the fluorescence intensity in ALA-treated tumorur tissue and normal skin was calculated for each patient and the mean values in each group were evaluated as a function of ALA applicaytio time in addition the fluorescence intensity variation in ALA-treated normal skin adjacent to ghe tumor was assesed The results fromthsi study show a peak of te mean contrast values after 3h ALA application but due to large interpatient variatin the mean contrast did not differsignificantly in te interval 2-4 h AFTER 2h ALA applicatinis not preferable when using PDD Based on data fo the fluorescence variation in ALA-treated normal skin after 3 adn 4h ALA application a toleance interval was calculated implying that values above 1.4 times the mean mormal fluorescence indicate an abnormal conditin this tolerance limit agrees well with results obtained in a former study.