SU‐E‐T‐772: Volume Matching for Brachytherapy Planning

Abstract

Purpose: To perform brachytherapy treatment plan by comparing it with existing data base from earlier treatments of similar type. Method: When brachytherapy target to be treated is closely related in shape and volume to the target treated in the past for which we had well developed plan based on sources energy, activity and spatial distribution we can assume that plan of essentially the same quality will be achieved when the same distribution of sources that was used in the past will be imposed over the new, identical to one in the past treatment volume. The planning strategy under these circumstances relies on matching the volume under consideration with the volume of the target from earlier treatment. Characteristic scalar parameters of volumes will be compared first to filter the database (these will include volume, orientation of principal axes and moments of the characteristic set of the compared volumetric domains). When these parameters match closely between considered volume and one of stored in library volumes they are suspect of close similarity. The next stage of comparisons matches volumes by translating them in 3D space so that the maximal intersection between them is achieved. When closeness criterion is satisfied for this matching the distribution of sources is moved from the old plan to the new target completing the planning process. Results: The program for the algorithm has been written and sequence of plans have been computed for dose distributions obtained by sources placement based on domain comparison planning described above. Conclusion: The excellent agreement between set of plans based on geometrical planning approach and traditional planning optimization approach has been discovered. The domain comparison planning leads to enviable dose distribution in brachytherapy treatment and it is fast enough to be applicable to real time treatments.