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Background and purpose: The use of stereotactic ablative radiotherapy (SABR) for prostate cancer has increased significantly. However, SABR can elevate the risk of moderate gastrointestinal (GI) side effects. Rectal spacers mitigate this risk by reducing the rectal dose. This study evaluates the impact of rectal spacers in MR-guided adaptive radiotherapy (MRgART) for prostate SABR. Materials and methods: A retrospective analysis was conducted on twenty patients with localised prostate cancer treated on the Unity MR-Linac at a single centre. Half of the cohort (n = 10) had rectal spacers placed before treatment. The adapt-to-shape strategy was used for online MRgART, and non-adapted plans were later generated offline for comparison. Dosimetric assessments were made between spacer and no-spacer cohorts, and between online adapted and non-adapted plans. Clinician-reported outcomes for genitourinary (GU) and GI toxicity were assessed at 3-, 6-, and 12-months post-treatment using Common Terminology Criteria for Adverse Events v.5.0. Results: No grade 2 or higher toxicity was observed in either cohort. Overall, the dosimetric analysis showed comparable results between the cohorts for target volumes, with D95% of 36.3 Gy in the spacer cohort and 36.0 Gy in the no-spacer cohort (p = 0.08). The spacer cohort demonstrated significant benefits in all rectal dose objectives (p

Abstract The introduction of magnetic resonance (MR) linear accelerators (MR‐Linacs) into radiotherapy departments has increased in recent years owing to its unique advantages including the ability to deliver online adaptive radiotherapy. However, most radiation oncology professionals are not accustomed to working with MR technology. The integration of an MR‐Linac into routine practice requires many considerations including MR safety, MR image acquisition and optimisation, image interpretation and adaptive radiotherapy strategies. This article provides an overview of training and credentialing requirements for radiation oncology professionals to develop competency and efficiency in delivering treatment safely on an MR‐Linac.

Abstract The introduction of magnetic resonance (MR) linear accelerators (MR‐Linac) marks the beginning of a new era in radiotherapy. MR‐Linac systems are currently being operated by teams of radiation therapists (RTs), radiation oncology medical physicists (ROMPs) and radiation oncologists (ROs) due to the diverse and complex tasks required to deliver treatment. This is resource‐intensive and logistically challenging. RT‐led service delivery at the treatment console is paramount to simplify the process and make the best use of this technology for suitable patients with commonly treated anatomical sites. This article will discuss the experiences of our department in developing and implementing an RT‐led workflow on the 1.5 T MR‐Linac.

Abstract Introduction This study aimed to develop a single‐isocentre volumetric modulated arc therapy (si‐VMAT) technique for multiple brain metastases using knowledge‐based planning software, comparing it with a multiple‐isocentre stereotactic radiosurgery (mi‐SRS) planning approach. Methods Twenty‐six si‐VMAT plans were created and uploaded into RapidPlanTM (RP) to create a si‐VMAT model. Ten patients, with 2 to 6 metastases (mets), were planned with a si‐VMAT technique utilising RP, and a mi‐SRS technique on Brainlab iPlan. Paddick Conformity Index (PCI) was used to compare conformity. The volumes of the brain receiving 15Gy, 12Gy, 10Gy, 7.5Gy and 3Gy were also compared. Retrospective treatment times from the last eight patients treated were averaged for pre‐imaging and beam on time to calculate treatment times for both techniques. Results There was a significant difference in the PCI scores for the mi‐SRS plans (M = 0.667, SD = 0.114) and si‐VMAT plans (M = 0.728, SD = 0.088), with PCI values suggesting better prescription dose conformity with the si‐VMAT technique (P = 0.014). Percentage of total brain volume receiving low‐dose wash at four of the five different dose levels was significantly less (P