The easy and non-destructive fluorescence method for quantification of early changes in biological tissues improves the possibilities of the clinical research and diagnostics. Developments in this area are moving very rapidly in part because of advances in the technology and in part because of the numerous successful examples which are appearing. New family of photomultiplier tubes with a high detection sensitivity for near-infra red light (700-900 nm) were developed as a result of project IMPECABLE, which are valuable tools for early diagnosis of cutaneous pigmented melanoma using long-wave fluorescence dyes.
Several phthalocyanines that are promising fluorophores for photodiagnosis of cutaneous malignant melanoma have been studied in different solvents for concentrations from 10-5 to 10-15 mol. Argon pumped dye laser as an excitation source was used. Three different wavelengths (613, 633 and 660 nm) in the red region, corresponding to first absorption peak, minimum of the absorption and near to the Q-band maximum of Pcs were applied. Fluorescence signals in the region of 700 to 800 nm were detected using spectrometric systems (Perkin-Elmer, UK-with conventional PMT as a detector, and PC2000, Ocean Optics, USA-with CCD-array as a detector) and a newly developed red-sensitive PMT. Detectable signal from other spectrometric systems was obtain up to 10-8 mol concentrations, which could be used for significant reduction of concentrations applied for in vivo applications.
Fluorescence is a highly sensitive method of distinguishing between healthy and unhealthy tissue. The results demonstrate that extremely low concentrations of photosensitizers could be used to determine initial stages of melanoma. This application of PMT detectors will reduce extremely the negative side effects of higher concentrations of these drugs applied in the skin tissue. One can achieve high accuracy in the determination of pigmented malignant melanoma lesions with wide clinical applications.