ESTRO 2021 Abstract Book

S218

ESTRO 2021

Results Dosimetrically, the clinically deliverable Novel plans with only 25 beams (Novel25) were highly similar to the 91-beam ideal reference plans (see population averaged DVHs in Fig. 1). On the other hand, the Novel25 plans were clearly of higher quality than the Clinical treatment plans that had on average 45 beams. Especially, for rectum and bladder sparing, the plans generated with the novel BAO method outperformed the Clinical plans. The average estimated delivery time of Novel25 plans of 18 min [14 – 28] also compared favorably with Clinical, the latter with a delivery time of 21 min [ 17 – 32]. Although the quality of Novel plans improved with increasing pre-set maximum beam numbers, moving towards the ideal reference plans, for rectum and bladder these improvements started to level off around 15-20 beams (Fig. 2). The average total calculation time over all Novel plans was 4.9 hours [3.2 – 7.7].