ESTRO 2021 Abstract Book

S129

ESTRO 2021

The differences between the different protocols to obtain the dose at the surface of a water phantom could be significant and confirm the need for further research to obtain a correct calibration in the clinic for those eBT sources.

Proffered papers: Proffered papers 12: Adaptive RT: Proton

OC-0200 Patterns Of Practice in Adaptive and Real-Time Particle Therapy, Part I: intrafractional motion Y. Zhang 1 , P. Trnkova 2 , B. Heijmen 3 , C. Richter 4 , M. Aznar 5 , F. Albertini 1 , A. Bolsi 1 , J. Daartz 6 , J. Bertholet 7 , A. Knopf 8,9 1 Paul Scherrer Institut, Center for Proton Therapy, Villigen-PSI, Switzerland; 2 Medical University of Vienna, Department of Radiation Oncology, Vienna, Austria; 3 Erasmus Medical Center, Department of Radiotherapy, Rotterdam, The Netherlands; 4 Technische Universität Dresden, OncoRay – National Center for Radiation Research in Oncology, Dresden, Germany; 5 University of Manchester, Division of Cancer Sciences, Faculty of Biology, Medicine and Health,, Manchester, United Kingdom; 6 Massachusetts General Hospital, Department of Radiation Oncology, Boston, USA; 7 Inselspital, Bern University Hospital, University of Bern, Division of Medical Radiation Physics, Bern, Switzerland; 8 University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands; 9 Center for Integrated Oncology Cologne, University Hospital of Cologne, Department I of Internal Medicine, Cologne, Germany Purpose or Objective For particle therapy, the clinical implementation of Real-time Respiratory Motion Management (RRMM) is of vital importance to mitigate the detrimental effects of motion on dose delivery. We introduced a worldwide questionnaire on the Patterns of Practice for Adaptive and Real-Time Particle Therapy (POP-ART PT), aiming to determine the current status of (and the potential barriers to) motion management implementation in clinical practice at particle therapy centers. Here we summarize the results concerning RRMM implementation at European centers. Materials and Methods A questionnaire was distributed worldwide to evaluate the current clinical practice, wishes for expansion and barriers to new implementation, targeting all particle therapy centers in operation as recorded by Particle Therapy Co-Operative Group. Two types of RRMM technique were considered: 1) volumetric/layered rescanning, 2) active RRMM, using free-breathing gating, breath-hold (BH), or tracking/motion synchronization. The tumor sites breast, lung, liver, pancreas, esophagus, and lymphoma were specifically surveyed. Results Responses from 23 centers (13 countries) were received out of the 25 European centers approached (92% response rate). RRMM was used in 16(69%) centers clinically, of which 5(22%) use both rescanning and active RRMM (figure 1). Of the 22 centers using pencil beam scanning, 13(56%) were applying rescanning, 7(31%) indicated the plan to implement it in the future, and 2(9%) reported rescanning incompatibility due to machine limitations. However, no consistent optimal rescanning method was found, as 6/7 centers used layered/volumetric rescanning with large variations in rescan numbers (2-6 times). Only 8(34%) centers have been using BH/gating as active RRMM in at least one tumour site (Lymphoma: 100%), but all centers wished to implement it in the future. Surface motion or breathing volume monitoring was the most common method to guide active RRMM. Four centers provided audio/visual feedback to the patient with 2 acquiring additional images to verify surrogate accuracy online. No center conducted a training session to improve breathing reproducibility. No center used or wished to use tracking/motion synchronization in the future. Furthermore, 12(54%) and 20(87%) centers wished to extend the use of active RRMM for current tumour sites and to implement it for new tumour sites, respectively. Priority was given to lung (58% and 83%). The main barriers (figure 2) to extend/implement RRMM for current/new tumour sites were technical limitations, limited equipment and human resources.