the invention relates to a method (200) for assistance in the planning of treatment by photodynamic therapy of a patient.when a photosensitive substance, shall be administered to the patient.then the illumination at a wavelength determined by the intermediary of a number of optical fibers can be introduced over a length of insertion in the treatment area, saltwe have a position relative to a grid of brachytherapy.the process achieves a step (230) of the size of the area to be treated with volume reconstruction from contours before digital processing of the digital image directly to a series ofthe area to be treated, and a determination (250) for the calculation of the number of optical fibers to be used.their position in relation to the structure and length of the insertion of brachytherapy, which optimize the match of a total volume of theoretical calculated from the measured volume of work, the zoto deal with the total volume of theoretical work is calculated on the basis of the position of each fiber.and a basic volume of action corresponding to the theoretical fiber volume of a cylinder of radius r and height corresponding to a predetermined length of insertion of the fiber.the invention also relates to a method (100) for modelling the radius of an optical fiber using a correlation of measured volumes of necrotic areas in response to a plurali effectivelyresearch trials in different patients with the same theoretical volumes calculated from sets of parameters used in clinical trials and the basic volumea theory of action of fiber.Linvention concerne un procédé (200) dassistance à la planification dun traitement par thérapie photodynamique dun patient, lors duquel une substance photosensible prédéfinie doit être administrée au patient, puis soumise à une illumination à une longueur donde prédéterminée par lintermédiaire dun nombre de fibres optiques aptes à être introduites sur une longueur dinsertion dans la zone à traiter selon une position par rapport à une gr
