The present invention relates to the field of radiation therapy. In particular, the invention relates to a method and a dose planning module for planning a treatment session of a patient by means of a radiation therapy system com¬ prising a radiation therapy unit having a fixed radiation focus point. The method according to the invention comprises: obtaining a target volume of a region of a patient to be treated during a treatment of a patient in a radiation therapy unit, the target volume being modeled as a three-dimensional voxel representation Selecting an isodose level for the planned treatment determining shots to be delivered during the treatment, each shot being modelled by a spatial dose volume distribution of radiation represented by a three-dimensional voxel representation, the shape of the spatial distribution depending on the specific collimator setting and the selected isodose level and selecting shots in a decreasing volume order for the dose planning comprising: d1) initiating a position search for a specific shot to find an accepted position within the target volume d2) iteratively mapping different positions for the voxel representation of a current shot on the voxel representation of the target volume d3) checking whether predetermined conditions for each specific position are satisfied and d4) if the predetermined conditions are satisfied for a specific position, defining that position as an accepted position and continue with step d1) - d3) for a shot having the similar shape or d5) if the predetermined conditions are not satisfied for any position within the target volume, continuing with step d1) - d4) for a subsequent shot in the decreasing volume order.La présente invention concerne le domaine de la radiothérapie. En particulier, linvention porte sur un procédé et sur un module de planification de dose en vue de la planification dune session de traitement dun patient au moyen dun système de radiothérapie, comprenant une unité de radiothérapie
