Development and verification of a time delivery model for prostate intensity modulated radiotherapy using a Siemens^®...

Time delivery models thus far proposed for prediction of radiotherapy delivery times are not applicable to all makes of Linac. Our purpose was to develop a time delivery model, which would also be applicable for a Siemens^® ARTISTE™ 160 Multi-leaf Collimator (MLC) linear accelerator (Linac) and validate the model using prostate Intensity Modulated Radiation Therapy (IMRT) treatment plans. To our knowledge, a time delivery model has not yet been proposed for a Siemens^® ARTISTE™ 160 MLC Linac. We used the principles of the time delivery model created for a Varian^® Linac and added the radio frequency (RF) wave component, and the MLC delay time to the MLC travel time component. Machine input parameters were confirmed using a WIN^® stopwatch. We tested our derived model by selecting ten random 15 MV prostate IMRT treatment plans from our clinic. The delivery time was measured three times, once per day on three different days. The calculated and measured times were compared by means of correlation. The time delivery ranged between 314 and 480 s. The largest percentage difference was 3.3% (16 s) and the smallest 0.2% (1 s); the mean percentage difference was 1.9%. MLC delay and MLC speed, representing segment delivery, had the greatest uncertainties. From the successfully verified time delivery model created, it is concluded that the inter-segmental component of the process is most time-consuming. In order to decrease delivery time it is proposed that the total segments of a treatment plan be decreased.