Weryfikacja planów leczenia dla urządzenia Gamma Knife za pomocą metod eksperymentalnych stosowanych w fizyce jądrowej

Abstract

The stereotactic radiosurgery is a modern method of treatment of pathological changes in the head region of a patient, based on a high radiation dose delivered to a target volume during one fraction. The device used in this type of therapy is the Leksell Gamma Knife Perfexion which has 192 sources of Co-60 with the solid collimators. It makes it possible to reach a precision better than 0.05mm. The purpose of this work was verification of the treatment plans for the therapy by means of the Leksell Gamma Knife Perfexion device, using the nuclear physics experimental methods. Two measuring methods were applied i.e. thermoluminescence dosimetry and the method basing on the dosimetry films. These methods are widely applied in the clinical dosimetry. Additionally the treatment plans were analyzed with the use of the commercial software MuCheck called the dose calculator by Data Oncology System. Two dose algorithms: TMR10 and Convolution available to the treatment planning system were verified. Two original phantoms: the Film Holder Spherical phantom and the author's modified anthropomorphic phantom provided with the apparatus were applied. Additionally the absorbed dose measurement was performed during the computed tomography study, using the TLD method. The performed verification of plans indicated that there were not any significant discrepancies between the measured doses and the ones calculated by means of two independent algorithms of the treatment planning system. The observed differences do not exceed a sum of an experimental error and a calculation uncertainty. The main disadvantage of the used methods is relatively long time of the measurements. It does not make it possible to apply these experimental methods between the prepare of the treatment plan and the start of the treatment. However they can be used for a spot checks of the treatment plans, for example, during internal clinical audits. The recalculation of doses by means of the MuCheck calculating algorithm is enough for verification of the treatment plans for everyday use.