Ex vivo clinical measurement of the optical penetration depth in digestivetissues

The optical penetration depth of 120 biopsy samples taken from normal or ne oplastic digestive tissues is measured by means of a device which can be us ed in a clinical environment, is easy to handle and delivers results quickl y. It is seen that, at 655 nm, values of the penetration depth are centred around 1.1 mm and that they can vary by roughly a factor of 2 between sampl es of a given kind of tissue. This latter result suggests performing indivi dual measurements immediately before carrying out photodynamic therapy.