Proposal and Evaluation of a Physician-Free, Real-Time On-Table Adaptive Radiotherapy (PF-ROAR) Workflow for the MRIdian MR-Guided LINAC

Abstract

With the implementation of MR-LINACs, real-time adaptive radiotherapy has become a possibility within the clinic. However, the process of adapting a patient’s plan is time consuming and often requires input from the entire clinical team, which translates to decreased throughput and limited patient access. In this study, the authors propose and simulate a workflow to address these inefficiencies in staffing and patient throughput. Two physicians, three radiation therapists (RTT), and a research fellow each adapted bladder and bowel contours for 20 fractions from 10 representative patient plans. Contouring ability was compared via calculation of a Dice Similarity Index (DSI). The DSI for bladder and bowel based on each potential physician–therapist pair, as well as an inter-physician comparison, exhibited good overlap amongst all comparisons (p = 0.868). Plan quality was compared through calculation of the conformity index (CI), as well as an evaluation of the plan’s dose to a ‘gold standard’ set of structures. Overall, non-physician plans passed 91.2% of the time. Of the eight non-physician plans that failed their clinical evaluation, six also failed their evaluation against the ‘gold standard’. Another two plans that passed their clinical evaluation subsequently failed in their evaluation against the ‘gold standard’. Thus, the PF-ROAR process has a success rate of 97.5%, with 78/80 plans correctly adapted to the gold standard or halted at treatment. These findings suggest that a physician-free workflow can be well tolerated provided RTTs continue to develop knowledge of MR anatomy and careful attention is given to understanding the complexity of the plan prior to treatment.

Online adaptive MR-guided radiotherapy: Conformity of contour adaptation for prostate cancer, rectal cancer and lymph node oligometastases among radiation therapists and radiation oncologists

“…Regarding an MR-Linac ATS workflow, Willigenburg et al analyzed RTT-derived prostate CTV and OAR delineations [13]. Different to our study, online contour adaptations performed by RTTs were Since the introduction of oMRgRT, some studies described the important role of RTTs for online treatment approaches [11,23,24]. Hales et al described a novel 'clinician-lite' prostate treatment adapt-toposition (ATP) MR-Linac workflow, with a prominent role for RTTs [23].…”

“…Another study found DSCvalues over 0.96 for OAR recontouring by two ROs, three RTTs and one research fellow in 10 patients with pelvic tumor sites. Subsequent non-physician treatment plans were acceptable in only 91.25 %, but in 97.2 % if one complex case was excluded, leading to the conclusion that the most complex oMRgRT treatments might be excepted for RTT-led workflows [24].…”

Patient specific contouring region of interest for abdominal stereotactic adaptive radiotherapy

“…This contouring assessment is also site, dose, and clinical scenario dependent which further limits a single approach for all scenarios. For example, there are suggestions of contouring all OARs within 2 cm of prostate targets or 1.5 cm superior to bladder targets [14] , [15] . For pancreas, machine-learning applications determined contouring extent (3 cm radial) for pancreatic stereotactic ART but was developed for a now obsolete MR-guided cobalt machine [6] .…”

Old dogs, new tricks: MR‐Linac training and credentialing of radiation oncologists, radiation therapists and medical physicists

“…Centres globally are moving towards RT‐led treatment workflows, making the traditional RT role more specialised. 16 , 17 , 18 , 19 , 20 …”