ESTRO meets Asia 2024 - Abstract Book

S340

Physics – Quality assurance and auditing

ESTRO meets Asia 2024

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300 VMAT SBRT/SRS plans were analyzed after applying the exclusion criteria. This study included radiotherapy patients handled by 9 radiation oncologists while treatment plans were performed by 4 radiotherapy medical physicists. The disease sites distribution was 34.0% for lung, 20.7% for brain, 19.6% for prostate, 13.0% for bones, 7.7% for pelvic soft tissue, and 5.0% for liver. The treatments consisted of 3, 5, and 6 fractions while dose per faction varied from 5 to 13 Gy. The PTV volume variability per disease site is shown in Fig. 1. The smallest median volume of 9.4 cc was for brain cases, while the largest of 107.2 cc for prostate ones. In Fig. 2 the dependence of delivered MU (normalized to the prescription dose per fraction, MU/cGy) on the PTV volume of the treatment site is shown. Fig. 2 illustrates that for large volume prostate cases the corresponding SBRT plans had 37% more MU than the mean amount of MU for other cases.