[Poster] Utilisation d’un Logiciel de Dosimétrie Portale pour l’Evaluation des Plans de Traitement « Step and Shoot » sur les Accélérateurs Elekta*

Introduction: Portal dosimetry is largely used to check treatment plans with modulated beams particularly in the case of Varian Linacs due to the PDIPTM software. It is very quick and gives results that are comparable to the classical verification methods. Dosisoft Company has developed a portal dosimetry software EPIBEAM^TM allowing to perform the same type of controls on Elekta machines. The aim of this study is to evaluate the feasibility of these controls in the particular case of modulated beams in “step and shoot” mode as a function of the different image acquisition modalities available on the IViewGTTM portal imager.

Materials and method: Typical treatment plans from patients treated in our institution using “step and shoot” beams have been irradiated using the different acquisition modes available on the IViewGT. The images were analyzed in EPIBEAM using the recommended evaluation criteria (absolute dose and gamma index). To determine the optimal analysis conditions, several mode of evaluation have been explored and compared particularly by analyzing the images on a segment per segment basis with summation of the results or directly using the integrated mode.

Results and conclusion: The results of this study will be described and reported regarding the different acquisition modalities of the images. Each of them are dependent on the management of the image calibration (pixel factor). This control method present many advantages like simplicity and speed of execution. The portal imager resolution ensure a good precision of the results and makes it efficient in the case of intensive use of IMRT treatments.