{'fraction_non_alphanumeric': 0.018072289156626505, 'fraction_numerical': 0.0, 'mean_word_length': 6.0423728813559325, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Imaging of tumors by time-delayed laser-induced fluorescence

A technique to improve signal-to-background ratio in fluorescence images of superficially growing tumors marked with photosensitizers is described. Time-delayed detection of fluorescence following pulsed-laser excitation allows suppression of the autofluorescence background falling into the fluorescence band of the photosensitizer. This technique exploits the longer fluorescence-decay times of porphyrin-based photosensitizers compared to average decay times of tissue autofluorescence. The feasibility of time-delayed fluorescence imaging of tumors has been demonstrated in vitro. From time-delayed fluorescence spectra the authors infer that the ratio between photosensitizer signal and autofluorescence background can be improved by about one order of magnitude.