Tissue characterization in some clinical specialities utilizing laser-induced fluorescence

Laser-induced fluorescence (LIF) can be used for non-invasive spectroscopic identification of biological tissue and is of special interest in early tumour detection. The basis for this 'optical biopsy" method is the interaction of the laser light with tissue chromophores, such as tryptophan, collagen, elastin, NADH, f3-carotene and haemoglobin. The UV-excited fluorescence that arises from the native chromophores, the autofluorescence, has a broad distribution, peaking at about 490 nm with a lower intensity in tumour compared to normal tissue. The tumour detection potential is enhanced with exogenously administrated tumour marking agents, such as Haematoporphyrin (HPD, commercial name Photofrin), with two fluorescence peaks at about 630 and 690 nm. We have developed clinical instrumentation both for tissue point monitoring and for full real-time image processing. Seventy-one patients were investigated in vivo and surgical samples from additional 20 patients. In 46 patients the autofluorescence only was monitored. In 45 patients lowdose Photofrin injection was used. The in vivo investigations included different kinds of lung tumours (30 patients), urinary bladder tumours (2 1 patients) and malignant gliomas (20 patients). The in vitro measurements were performed in breast tumours (15 patients) and prostatic tumours (5 patients). Invasive and early tumours and also precancerous lesions can be revealed utilizing LIF in low-dose Photofrin injected patients.