ESTRO 2024 - Abstract Book

S4144

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2024

Of 123 total treatment fractions, the adapted plan was chosen for 122 fractions. The mean treatment time from the start of the CBCT to the end of treatment delivery was 20.23 minutes. The influencer review is the most time consuming step of the process and has the greatest variability (mean 9.4min, SD 2.13min). For all patients, the PTV coverage was improved and more homogenous. As an example, for patient 2 (see DVH variability fig. 1, 2) the mean doses for adaptive versus scheduled were 95% for the PTV_HD (high dose PTV) compared to 94.1% (p<0.00001), 95.1% for the PTV_MD compared to 93.2% (p<0.00001), and 96.2% for the PTV_LD compared to 95.7% (p<0.0048). A statistically significant decrease in OAR dose was observed for OARs that did not overlap with the PTVs e.g., Dmean for contralateral parotid was 23.4Gy adapted versus 28.4Gy scheduled. In other patients with OARs overlapping with the PTV the dose was comparable to the reference plan.