TISSUE PHOTOSENSITIZER DETECTION BY LOW-POWER REMITTANCE FLUOROMETRY

A simple adaptation of a commercial spectrofluorimeter which allows th e semiquantitative determination of photodynamic therapy photosensitiz er fluorescence in accessible tissues is described. Light from a xenon lamp is directed via a monochromator onto the tissue surface by a bif urcated random fibre bundle. Tissue fluorescence is directed to the em ission monochromator and photomultiplier of the fluorimeter by the sec ond limb of the fibre bundle. Although relatively simple, this device can be used to carry out a wide range of useful measurements in clinic al and experimental photodynamic therapy. The sensitivity and reproduc ibility of the measurements were determined using mouse tumour and mus cle tissue fluorescence measured in vivo compared with photosensitizer content measured by high performance liquid chromatography. As an ill ustration of the potential applications of such systems, the time cour ses of fluorescence in the skin of patients treated with the photosens itizers Photofrin(R) and metatetra(hydroxyphenyl)chlorin (mTHPC) (temo porfin) and the photobleaching of 5-aminolaevulinic acid-derived proto porphyrin IX during treatment, are described.