The invention relates to an assistance method (200) for planning of a treatment with photodynamic therapy for a patient, during which a predetermined photosensitive substance must be administered to the patient and then subjected to illumination at a predetermined wavelength through a number of optical fibers adapted to be introduced over a length of insertion into the treatment area according to a position relative to a brachytherapy grid. The method performs a measurement (230) of the volume of the treatment area by volume reconstruction from digital processing of contours inputted directly into a series of digital images of the area being treated, then a determination (250) made by calculating the number of optical fibers used, their position relative to the brachytherapy grid and their insertion length which optimizes the correspondence of a total theoretical action volume calculated with the measured volume of the treatment area, the total theoretical action volume being calculated based on the position of each fiber, and an elementary theoretical action volume of a fiber corresponding to the volume of a cylinder with predetermined action radius R, and height corresponding to the insertion length of the fiber.The invention also relates to a modeling method (100) of the action radius of an optical fiber using a correlation of measured volumes of actual necrotic areas from a plurality of clinical trials on patients with different theoretical volumes calculated from the same sets of parameters used in clinical trials and the elementary theoretical action volume of a fiber.本發明係關於病患之光動力治療處置之規劃的輔助方法(200),於光動力治療處置期間必須將預定之光敏性物質施用於該病患,然後接受通過許多經調適而要根據與近接治療柵之相對位置被以一段嵌入長度導入處置區之光學纖維之預定波長照射。該方法藉由從直接輸入成正處置之區域的一系列數位影像的輪廓之數位處理而重建體積來進行處置區域之體積的測量(230),然後藉由計算所使用之光學纖維數來決定(250)該等光學纖維相對於該近接治療柵之位置及使以測得之處置區域的體積所計算的總理論作用體積之相關性最佳化的嵌入長度,該總理論作用體積係根據各纖維之位置計算,纖維之基本理論作用體積對應於具有預定作用半徑R之圓柱形的體積,且高度對應於該纖維之嵌入長度。本發明亦關於利用來自複數個對病患進行臨床試驗所測得實際壞死區域體積與從臨床試驗中所用相同參數組及纖維的基本理論作用體積所計算出來的不同理論體積之關聯性而將光學纖維的作用半徑模型
