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Interactions lumière-tissu dans le diagnostic et le traitement du cancer de la vessie

Abstract : Photodynamic therapy (PDT) is a treatment modality which results from the light interaction with a photosensitizer in the presence of oxygen. The ultimate objective of such a treatment is to destroy the tumor with the least damage to surrounding healthy tissues. Treatment parameters optimisation allows for a satisfactory therapeutic outcome. Intravesical instillation of hexaminolevulinate (hALA) at 8 and 16 mM in the rat bladder induces the transient synthesis of protoporphyrin IX (PpIX) in healthy and tumor bladder epithelium with comparable fluorescence concentrations and intensities, two and three hours after the end of one hour of hALA instillation. Bladder irradiation at 630 nm and 20 J/cm2 (100mW/cm2) induces complete tumor destruction without damage to adjacent epithelium and bladder wall at 8 mM and 20 J/cmZ. Contrarily, at 16 mM, irradiation with the same treatment conditions did not result in tumor destruction where total wall necrosis was observed. A two-fold faster photobleaching kinetic at 16 rnM compared to 8 mM which coincides with a diffuse cytoplasmic distribution of PpIX at 16 mM compared to localized distribution at 8 mM could explain the inversed treatment outcome. Cell viZio is a fibered confocal fluorescence imaging device dedicated to non invasive in situ and in vivo endoscopic confocal microscopy using miniaturized fiberoptic probes. Endoscopic examination of the healthy bladder allows the distinction of the three cell types present in normal rat urothelium after intravesical instillation of Rhodamine 123 (100pM, 30mn). Individual tumor cells could not be demarcated due to the fluorescence signal saturation and the entire tumor appeared as brightly homogenous fluorescence blot, surrounded by small inflammatory cells. This technique allows the differentiation of the normal from the transformed epithelium. An ideal bladder tumor model should produce a unique tumor, surrounded by a normal epithelium with a predictable localization and stage. Focal epithelial destruction followed by focal or global cell implantation produces intraepithelial tumors, surrounded by normal epithelium, however, covered by 1-3 normal cell layers.
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Submitted on : Thursday, March 29, 2018 - 10:48:51 AM
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Sami El Khatib. Interactions lumière-tissu dans le diagnostic et le traitement du cancer de la vessie. Biologie cellulaire. Université Henri Poincaré - Nancy 1, 2005. Français. ⟨NNT : 2005NAN11315⟩. ⟨tel-01746972⟩



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