Prospective Clinical Feasibility Study for MRI-Only Brain Radiotherapy

Minna Lerner; Joakim Medin; Christian Jamtheim Gustafsson; Sara Alkner; Lars E Olsson

doi:10.3389/fonc.2021.812643

Prospective Clinical Feasibility Study for MRI-Only Brain Radiotherapy

Front Oncol. 2022 Jan 10:11:812643. doi: 10.3389/fonc.2021.812643. eCollection 2021.

Authors

Minna Lerner^{1

2}, Joakim Medin^{1

3}, Christian Jamtheim Gustafsson^{1

2}, Sara Alkner^{1

4}, Lars E Olsson^{1

2}

Affiliations

¹ Department of Hematology, Oncology, and Radiation Physics, Skåne University Hospital, Lund, Sweden.
² Department of Translational Medicine, Medical Radiation Physics, Lund University, Malmö, Sweden.
³ Department of Medical Radiation Physics, Clinical Sciences, Lund, Lund University, Lund, Sweden.
⁴ Department of Clinical Sciences Lund, Oncology and Pathology, Lund University, Lund, Sweden.

Abstract

Objectives: MRI-only radiotherapy (RT) provides a workflow to decrease the geometric uncertainty introduced by the image registration process between MRI and CT data and to streamline the RT planning. Despite the recent availability of validated synthetic CT (sCT) methods for the head region, there are no clinical implementations reported for brain tumors. Based on a preceding validation study of sCT, this study aims to investigate MRI-only brain RT through a prospective clinical feasibility study with endpoints for dosimetry and patient setup.

Material and methods: Twenty-one glioma patients were included. MRI Dixon images were used to generate sCT images using a CE-marked deep learning-based software. RT treatment plans were generated based on MRI delineated anatomical structures and sCT for absorbed dose calculations. CT scans were acquired but strictly used for sCT quality assurance (QA). Prospective QA was performed prior to MRI-only treatment approval, comparing sCT and CT image characteristics and calculated dose distributions. Additional retrospective analysis of patient positioning and dose distribution gamma evaluation was performed.

Results: Twenty out of 21 patients were treated using the MRI-only workflow. A single patient was excluded due to an MRI artifact caused by a hemostatic substance injected near the target during surgery preceding radiotherapy. All other patients fulfilled the acceptance criteria. Dose deviations in target were within ±1% for all patients in the prospective analysis. Retrospective analysis yielded gamma pass rates (2%, 2 mm) above 99%. Patient positioning using CBCT images was within ± 1 mm for registrations with sCT compared to CT.

Conclusion: We report a successful clinical study of MRI-only brain radiotherapy, conducted using both prospective and retrospective analysis. Synthetic CT images generated using the CE-marked deep learning-based software were clinically robust based on endpoints for dosimetry and patient positioning.

Keywords: MRI-only; brain; cancer; glioma; implementation; radiotherapy; sCT.