ESTRO 38 Abstract book

S9 ESTRO 38

edited, which is very time consuming. This delay could compromise the treatment efficacy due to intra-fractional anatomical changes happening while the patient is lying on the couch. The question to be addressed in this talk is how we could perform quality checks on the daily contours to guarantee safe treatment delivery. To elaborate on that, metrics used to assess contour quality will be discussed, as well as the link between geometry and dosimetry to determine the areas where contours need to be more accurate. For contours propagation, strategies specifically defined for adaptive pathways will be discussed; and general issues with contour generation will be considered. SP-0031 QA of deformable image registration Marc Kessler 1 1 University of Michigan, Radiation Oncology, Ann Arbor, USA Abstract text Combined hardware and software systems are now available at the treatment unit to support daily dose assessment and enable on-line adaptive radiotherapy using image registration and data fusion to propagate contours and accumulate dose across image data acquired throughout patient treatment. The goal of these systems is to provide up-to-date estimates of anatomical changes and delivered dose. This information aids in the detection of changes that may demonstrate a clinical need to modify the original treatment plan or prescription. As the output of the image registration process is always used as the input of another process for planning or delivery, it is important to understand and communicate the uncertainty associated with this process, both in general and for a specific registration. Unfortunately, there is no standard mathematical formalism to perform this analysis in actual clinical situations where overall uncertainty conflates image noise and distortion with underlying algorithm bias and complex anatomical variations. Validation of registration performance is also complicated by the lack of documentation available for commercial systems leading to use of these systems in a less-than-desirable ‘black-box’ fashion. In view of this situation and the central role that image registration and data fusion play in various clinical workflows, the Therapy Physics Committee of the American Association of Physicists in Medicine commissioned Task Group 132. The resulting report reviews current approaches and solutions for image registration and provides recommendations for quality assurance and quality control of these clinical processes. These recommendations and examples of their use for on-line adaptive radiotherapy will be presented. SP-0032 QA of on-line adaptive radiotherapy: Experience of The Royal Marsden Hospital S. Nill 1 1 The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, Joint Department of Physics, London, United Kingdom Abstract text In room MR image guidance enables the online adaptation of treatment plans based on the current patient anatomy while the patient is on the treatment couch. Therefore conventional methods like pre-treatment plan QA using a phantom to validate the treatment plan are no longer applicable. In 2016 The Royal Marsden NHS Foundation Trust and The Institute of Cancer Research installed the Elekta Unity system and the first patients were treated in September 2018. The Elekta Unity system consists of a 1.5T MR

Gy was delivered to the CTV. In summary, more evidence is coming for the need of image guided adaptive brachytherapy, preferably with MRI, in primary vaginal cancer. A prospective multicenter study is warranted to gain more knowledge about this rare disease. SP-0026 GYN GEC-ESTRO Recommendations for IGABT target delineation in primary vaginal cancer M.Schmid 1 1 Medical University of Vienna, Department of Radiotherapy, Vienna, Austria SP-0027 Brachytherapy for primary vaginal cancer – North American experiences M. Kamrava 1 1 Cedars-Sinai Medical Center, Radiation Oncology, Los Angeles, USA Abstract text While large prospective experiences with image guided adaptive brachytherapy (IGABT) are accumulating in definitive cervical cancer treatment there is more limited information on the impact of IGABT in the definitive management of vaginal cancers. There is no consensus regarding the ideal dose, definition of the high-risk clinical target volume, or definition of organs at risk (OAR) such as the vagina. The purpose of this talk is to review the literature from North America regarding IGABT for primary vaginal cancers with respect to dose, target/OAR definitions, and clinical outcomes. We will compare the North American experiences with those from Europe and finally review the North American experience with trying to find consensus regarding target definition. SP-0028 Dose planning for primary vaginal cancer – a multicentre comparison N.Nesvacil 1 1 Medical University of Vienna, General Hospital of Vienna- Vienna- Austria, Department of Radiation Oncology, Vienna, Austria Abstract not received

Abstract not received

Joint Symposium: ESTRO-AAPM: QA of on-line adaptive radiotherapy

SP-0029 Setting the scene S.Mutic 1 1 Washington University School of Medicine, Radiation Oncology- Physics Division, Saint Louis, USA

Abstract not received

SP-0030 QA of contour segmentation E.M. Vasquez Osorio 1

1 The University of Manchester, Division of Molecular & Clinical Cancer Studies- School of Medical Sciences- Faculty of Biology- Medicine and Health, Manchester, United Kingdom Abstract text Adaptive radiotherapy relies on fast identification of the structures (targets and organs at risk) on the daily image to adapt the treatment plan according to the patient’s anatomy on the day of delivery. Two main alternatives for identifying these structures are 1) propagation of contours from the planning image (CT scan/MR scan) into the daily image and 2) generating contours from scratch on the daily image. Contour propagation is the most commonly used and it is implemented in clinical adaptive pathways. No matter how the contours are created, they are manually