ESTRO 2025 - Abstract Book

S2915

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2025

achieved. As far as the ultra-fast ATS, the average planning time was 295s (100s to 520s) for H&N cases and 149s (60s to 280s) for brain cases. The longest planning time was related to the first fraction, i.e. that required to adapt the offline plan to the first daily MRI; all others fractions’ replanning took less time. We also noted a dependency of planning time on modulation degree optimization parameter of offline plan, with lower modulation degree producing a lower calculation time. Plan quality was always comparable to the usual ATS method, achieving the same dosimetric constraints (Figures 1 and 2).

Conclusion: Ultra-fast ATS is a promising strategy for MRgART which allows for a great reduction in calculation time with respect to classical ATS while maintaining a good plan quality. Adaptation is faster and easier for less modulated plans.

Keywords: MRgART, ATS, MR-linac