Detection of early bladder carcinoma by fluorescence cystoscopy with Hexvix: optical characterization of a high magnification cystoscope

Fluorescence detection of early superficial bladder cancer has been well established over the last years. This technique exploits the selective production and accumulation within cancerous tissues of photoactive porphyrins (PaP), mainly protoporphyrin IX (PpIX), after the instillation of hexaminolevulinic acid (Hexvix (R)) in the bladder. Although the selective production of PpIX and the sensitivity of this procedure are outstanding, its specificity is still limited by a relatively important proportion of false positive (FP) lesions. Cancerization process often combines with changes in vascular architecture. It is likely that the visualization of these modifications should allow us to differentiate false and true positive (TP). Therefore, our current research focuses on the characterization of positive sites by high magnification (HM) cystoscopy. This new method is investigated by our group to reduce the number of biopsies. In this study, we are using a dedicated rigid cystoscope, allowing conventional magnification during "macroscopic" white light and fluorescence observation, as well as image acquisition with HM when the endoscope is in contact with the tissue. This is realized by an optical setup directly integrated in the cystoscope. We describe here an off-clinics calibration procedure that will allow us to assess the vessel architecture and size once we use this optics to observe the bladder mucosa.