ESTRO 2025 - Abstract Book

S3215

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

ESTRO 2025

mean differences were -11.4%, -9.3%, and -5.6% for the 0 mm, 3 mm, and 5 mm margins respectively. An example of the delivered dose distributions is shown in Figure 2. The average 2%/2mm gamma-failure rates were 0.0% for dose-optimised and 2.5% for geometry-optimised MLC tracking, and the 1%/1mm gamma-failure rates were 1.2% for dose-optimised and 20.1% for geometry-optimised MLC tracking.

Conclusion: While accurate delivery of STAR is particularly challenging, preliminary findings indicate that dose-optimised MLC tracking accurately adapts radiation therapy to intrafraction motion, requiring minimal or no margins, and could enable a reduction in dose to healthy tissue.

Keywords: MLC tracking, dose optimised adaptation

References: 1. Cuculich, P.S., et al., Noninvasive Cardiac Radiation for Ablation of Ventricular Tachycardia. New England Journal of Medicine, 2017. 377(24): p. 2325-2336. 2. Lydiard, S., et al., Investigating multi-leaf collimator tracking in stereotactic arrhythmic radioablation (STAR) treatments for atrial fibrillation. Physics in Medicine & Biology, 2018. 63(19): p. 195008. 3. Mejnertsen, L., et al., Dose-based optimisation for multi-leaf collimator tracking during radiation therapy. Physics in Medicine & Biology, 2021. 66(6): p. 065027. 4. Wijesooriya, K., et al., Determination of maximum leaf velocity and acceleration of a dynamic multileaf collimator: Implications for 4D radiotherapy. Medical Physics, 2005. 32(4): p. 932-941.

1036

Poster Discussion Deep Learning-Based Framework for Liver Tumour Motion Detection Using Fiducial Markers in Kilovoltage X-ray Images Frances Kan 1 , Freeman Jin 1 , Adam Mylonas 1 , Benjamin Zwan 2 , Trang Nguyen 1 , Trevor Moodie 3 , Nick Hardcastle 4 , Prabhakar Ramachandran 5 , Daniel Mason 6 , Tim Wang 3 , Yoo Young Lee 5 , Paul Keall 1 , Chandrima Sengupta 1 1 Image X Institute, University of Sydney, Sydney, Australia. 2 Radiation Oncology, Central Coast Cancer Centre, Gosford, Australia. 3 Radiation Oncology, Crown Princess Mary Cancer Centre, Westmead, Australia. 4 Radiation Oncology, Peter MacCallum Cancer Centre, Melbourne, Australia. 5 Radiation Oncology, Princess Alexandra Hospital, Woolloongabba, Australia. 6 Radiation Oncology, Nepean Cancer and Wellness, Nepean, Australia