Optimization of 5-aminolaevulinic acid application and light excitation to ensure maximum contrast between cancerous and healthy tissue on the skin

This paper describes a low-cost system for the illumination and real-time imaging of skin lesions. The light source is a mercury arc lamp, filtered to preferentially excite the fluorescence of protoporphyrin IX (PpIX) formed within the skin after the topical application of 5-aminolaevulinic acid (ALA). A video camera with a reduced-frame-rate, i.e. integrating, enables low intensity fluorescence imaging. Appropriate filtering provides independent images of the illumination uniformity, PpIX fluorescence and autofluorescence. Subsequent image processing yields false color images of the tissue surface illustrating the extent of ALA application, tumor boarder, surrounding satellites and the possible demarcation of treatment zones.