Optical detection of human urinary bladder carcinoma utilising tissue autofluorescence and protoporphyrin IX-induced fluorescence following low dose ALA instillation

Laser-induced fluorescence spectra were recorded in patients undergoing urinary bladder cystoscopy. The measurements were performed in vivo and the spectra were collected from normal and diseased tissue. The patients were divided into two groups. An instillation of a 1% delta-amino-levulinic acid (ALA) solution was performed 2 - 4 hours prior to the investigation of one group of patients. A second group of patients was investigated without any tumor marking substance. The fluorescence was detected following laser excitation at 405 and 337 nm. Fluorescence emission related to ALA-induced protoporphyrin IX (PpIX) was detected in the ALA group for 405 nm excitation. The data were evaluated at the PpIX emission peak at 635 nm and at 490 nm, which approximately corresponds to the peak of the tissue autofluorescence. The data obtained with 337 nm excitation were evaluated at 400 and 460 nm as well as at 390 and 431 nm. The ratios of the respective wavelength pairs were formed in order to investigate the demarcation between tumor and normal tissue. The tumor demarcation results were better and more consistent utilizing the autofluorescence signal following excitation at 337 nm than the PpIX-related signal excited at 405 nm.