ESTRO38 Congress Report

Introduction Physics track

to achieve a coherent k Q

data set in the revised TRS- 398

The development of the physics tracks for ESTRO 38 has highlighted the major current trends in radiotherapy physics with a big increase in numbers of abstracts submitted on predictive modelling, radiomics and adaptive radiotherapy. There were also a very high number of submissions

protocol.

Finally Landry et al evaluated three different deep learning based correction strategies using neural networks for image correction in CBCT in terms of their photon and proton dose calculation accuracy. VMAT and proton pencil beam scanning (PBS) plans were optimized and recalculated on the corrected CBCT images. They concluded that training directly on corrected CBCT image slices is optimal for PBS proton dose calculations, while for VMAT all three correction strategies provided sufficient accuracy. Additionally the correction times were found to be fast enough for online adaptive RT workflows.

CATHARINE CLARK

on protons across all the different topics, but especially in planning, measurement and toxicity, suggesting that the implementation of proton treatment in Europe well underway. A significant increase in the use of MRI in pre- treatment planning, intra-fraction motion management and in radiomics was also seen. Overall extremely varied work was submitted, from fundamental dosimetry to radiobiological modelling to advanced imaging techniques. This led to very good number of abstracts submitted to all the topics and meaning that overall 826 abstracts were considered. This large number has meant that the number of proffered paper sessions has been increased for 2019. Over the following pages you will find five abstracts which have been selected to give you a taste of the breadth of the topics to come in the two physics tracks: The first was by Barragan Montero et al and looked at MRI only proton treatment planning with synthetic CT images generated using deep learning. This work used neural networks to quickly generate and validate the conversion to CT from MR images and using these images for proton planning. The differences between the plans on the synthetic and original CT were minimal implying that the synthetic CT could be used alone. Abravan et al used datamining to investigate the relationship between dose and the incidence of lymphopenia by identifying anatomical regions where the dose received by the tissue correlated with the lymphopenia. This work used an extensive dataset of 562 lung cancer patients to develop a model and identify the regions with lymphopenia of ≥G3. Multivariate analysis to identify the dose parameters and themodel was then validated on 301 oesophageal patients. The regression calculation showed that lymphopenia of ≥G3 predicted overall survival. MLC tracking for lung cancer SABR was investigated by Booth et al in a trial to determine clinical feasibility and measure the target and normal tissue doses in comparison with conventional SABR treatment. They showed that real-time adaptation using MLC tracking was feasible in seventeen lung cancer patients. Furthermore reductions in treated volumes up to 47% were seen, which translated to reductions in lung dose. Zink et al led a group of European national standards laboratories who have investigated the volume averaging correction, k vol , for a range of ion chambers in both flattened and non-flattened beams. The results showed that kvol, even for flattened beams, may be not negligible and the contribution to k Q should be indicated. They recommend that k Q should therefore be corrected for volume averaging

Catharine Clark Chair, SAG Radiation Physics

Congress report | PHYSICS

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