Modelling the action of one optical fiber in a treatment for photodynamic therapy and assistance for the planning of such treatment.The invention relates to a method (200) that provides assistance in planning the treatment of a patient with photodynamic therapy in a patient with treatment planning of photodynamic therapy.During which a photosensitive substance default should be administered in the patient and subsequently subjected to a light in a wave length preset by a number of optical fibers which can be inserted into a length of insertion in the area to be works of ACO RDO with affixed in relation to a grid of brachytherapy.The method comprises: the madi\u00e7\u00e3o (230) of the volume of the area to be treated by reconstruction of the volume on the basis of digital processing of contour inserted directly into a series of images digital processing of the area to be treated and subsequently, on the basis of the calculation of the n\u00famer The optical fibres to be used.Determine (250) the position of the optical fibers in relation to the grade of brachytherapy and the length of insertion of the same, which improves the correspondence between a total volume of action theoretical calculated and the measured volume of the area to be treated.The said volume of total action theoretical calculated as a function of the position of each fiber and a volume of theoretical elementary action of a fiber which corresponds to the volume of a cylinder that has height and radius of action predetermined r that correspode the length of insertion of the fiber.The invention also relates to a method for model 9100) the radius of action of one optical fiber with the use of a correlation of measured volumes of necrosed areas actually following a plurality of clinical trials carried out in different patients with the theoretical calculated in volumes. The basis of the same sets of parameters as those used in clinical trials and the volume of the action theorist heParliamentary one fib
