ESTRO 2024 - Abstract Book

S1943

Clinical - Mixed sites, palliation

ESTRO 2024

1729

Digital Poster

Clinical evaluation of 4DMRI in comparison to 4DCT for adults and children

Jessica L Gough 1,2 , Rosalyne Westley 1,2 , Joan Chick 3 , Evanthia Kousi 3 , Julie Hughes 4 , Georgina Hopkinson 4 , Erica Scurr 4 , Erika Pace 4 , Joshua Shur 4 , Rahouene Neji 5 , Andreas Wetscherek 2 , Uwe Oelfke 2 , Katharine Aitken 1,2 , Henry Mandeville 1,2 1 Royal Marsden Hospital, Radiotherapy, Sutton, United Kingdom. 2 Institute of Cancer Research, Radiotherapy and Imaging, London, United Kingdom. 3 The Royal Marsden Hospital and the Institute of Cancer Research, Joint department of physics, London, United Kingdom. 4 Royal Marsden Hospital, Radiology department, Sutton, United Kingdom. 5 Kings College Hospital, School of Biomedical Engineering and Imaging Sciences, London, United Kingdom

Purpose/Objective:

Optimising the accuracy and delivery of abdominal radiotherapy (RT) requires management of physiological target and organ motion, which is predominantly respiratory-related. When treating in free breathing, 4DCT is commonly used to define internal target volumes (ITVs). However, it is not always possible to acquire 4DCT, particularly when there is a low amplitude of chest wall motion including adults wearing abdominal compression or children, determined by external marker motion. Recently, 4DMRI has emerged as an attractive alternative given that there is no ionising radiation, it offers superior soft tissue contrast, no external marker is required, and it is self-gating. Despite significant interest in 4DMRI, there is little published experience on commercial products, which were recently released. We undertook work to optimise and validate a commercial 4DMRI prior to clinical implementation into abdominal RT workflows for adults and children at our centre. Following institutional board approval, patients were recruited to undergo 4DMRI as part of their RT planning protocol. Patients ≥5 years undergoing abdominal RT were included, provided they could tolerate the examination without sedation. All images were acquired on MAGNETOM Sola 1.5T (Siemens Healthcare, Erlangen, Germany) adopting the Siemens 4DMRI-RT Respiratory Self-Gating sequence(1) (a 3D T1-weighted gradient echo, self-gating, stack of stars radial acquisition with golden-angle increment — StarVIBE — sorted into 5 respiratory bins). Developmental phantom and healthy volunteer work at our centre highlighted concerns with craniocaudal motion under-estimation for axially acquired 4DMRI (4DMRI AA ), so initial focus was to optimise the coronally acquired version (4DMRI CA ). For the first 7 patients, stepwise alterations to 4DMRI CA parameters were made to optimise image clarity. From patient 4, 4DMRI AA were acquired in addition to 4DMRI CA . Material/Methods:

All patients were also referred for 4DCT and adults wore abdominal compression for all scans as per the standard workflow.