ESTRO 2021 Abstract Book

S99

ESTRO 2021

PH-0163 1.5 T MR Linac RO-Lite Workflow M. Jameson 1,2 , D. Crawford 3 , L. Hogan 3 , C. Loo 3 , T. Twentyman 4 , A. baker 3 , J. de Leon 5

1 GenesisCare, Medical Physics, Sydney, Australia; 2 University of New South Wales, Faculty of Medicine, Sydney, Australia; 3 GenesisCare, Radiation Therapy, Sydney, Australia; 4 GenesisCare, Global Partner Services, Sydney, Australia; 5 GenesisCare, Radiation Oncology, Sydney, Australia Purpose or Objective MR Linacs enable daily adaptive radiotherapy based on MR imaging. This allows the plan to be personalised to the patient’s anatomy at the time of treatment. This process condenses the usual days to weeks long planning workflow into minutes. Therefore, all of the usual staff groups represented in the planning workflow have historically been required at the treatment console. This is resource intensive and logistically challenging for services that span multiple locations. This study presents a RO-Lite workflow whereby only radiation therapists are present at the console for MR Linac treatment. Materials and Methods MDT meetings were held to determine appropriate cases for the RO-Lite workflow. A credentialing program was developed for RT training and sign off. Decision trees and tolerances were also determined via workshops and historical data. Results The RO-Lite workflow implemented initially for prostate cancer cases > 5 fractions. Elekta Unity has 2 workflow options, fully adaptive Adapt to shape (ATS) and virtual isocentre shift Adapt to position (ATP). ATS involves a full plan adaption with contouring and plan approval by the RO. When ATP is utilised, RT’s can lead the treatment session and call upon the RO when required (Figure 1). The first 10 fractions will be delivered with the ATS workflow to create a library of plans that can be selected for RO-Lite ATP. All RTs and ROs taking part in these treatments will have completed the required training and have been assessed as competent. Credentialing covers correct reference plan choice, image registration, identification of anterior wall of rectum, bladder volume assessment, understanding of decision tree and when to engage RO and planning goals. There are offline and online credentialing components.

Figure 1 RO-Lite workflow diagram showing decision points and tolerances

Conclusion A RO-Lite workflow has been developed and successfully implemented for non-SBRT prostate MR guided