ESTRO 2023 - Abstract Book

S510

Sunday 14 May 2023

ESTRO 2023

colli-DTRT plans are created for 1 brain (60 Gy to 50% of PTV), 1 lung (66 Gy to 50% of PTV), and 2 head and neck (HN, 50 Gy to 95% of PTV) clinically motivated cases with a total gantry angle range of 720°, and compared to a HDAO-optimized 2 full VMAT arcs plans using the same objectives. Results colli-DTRT plans comprised 9-17 partial arcs with a median 50° (min 30°- max 120°) gantry-angle range and table-angles covering the full available range. For the brain case, mean and near-max dose to the brain (excl. PTV) was 1.6 Gy lower, respectively 0.6 Gy higher for colli-DTRT than VMAT. Near-max dose to the brainstem was 55.6 Gy for colli-DTRT and 56.4 Gy for VMAT. For the lung case, the lungs and heart mean doses were on average 2.9 Gy lower for colli-DTRT than for VMAT (figure 2). For an oropharyngeal case (HN1), D5% to the PTV reached 55.2 Gy for VMAT and 53.5 Gy for colli-DTRT. Mean dose to the parotids, oral cavity, pharynx and larynx was on average 2.8 Gy lower for colli-DTRT than VMAT. For a nasopharynx case (HN2), near-max dose to the optic nerves, optic chiasm and eyes was on average 3.0 Gy lower with colli- DTRT than VMAT (figure 2).