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Fluorescence-based clinical diagnoses
Living tissues are naturally fluorescent. This is self-fluorescence caused by the presence of various excitable species in UV or visible light. The fluorescence of these compounds depends on the nature of the environment and can therefore be affected by pathological changes in the tissues.
The first experiments on self-fluorescence in vivo in humans began in the 1980s with the study of excitable flavins and riboflavins in visible light, and thus without the need for endoscopes equipped with optics adapted to UV light. Then the self-fluorescence of NADH in bronchi and stomach tissues was measured in patients with tumours : studies have shown that the intensity of self-fluorescence of NADH gets weaker as the tumour stage advances. This observation paved the way for the early detection of cancerous tumours using self-fluorescence (in the bladder, for example). Such a diagnosis is particularly interesting because the chances of success of therapies are as high as the level of invasion is low.
Sometimes, a fluorescent dye is injected as a tracer. It is the case of retinal angiography, where the fluorescence of a dye (fluorescein) is used to diagnose certain eye diseases (diabetic retinopathy, for example). This is an excellent way to check the state of retinal vessels and to detect possible neovessels (in the case of age-related macular degeneration) that may be treated using laser therapy (photocoagulation, for example).
Laboratoire de photophysique et photochimie supramoléculaires et macromoléculaires, CNRS-ENS Cachan
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