MRI-enhanced online adaptive radiotherapy by virtual integration of a standalone MRI simulator and CBCT-based treatment delivery.

Authors

Silvia Fabiano, Klara Kefer, Michael Baumgartl, Hubert Gabrys, Riccardo Dal Bello, Elizabeth Denney, Michael Mayinger, Jens von der Grün, Lotte Wilke, Matthias Guckenberger, Stephanie Tanadini-Lang, Sebastian M Christ

Published in

Radiation oncology (London, England). Jul 06, 2026. Epub Jul 06, 2026.

Abstract

MR-guided radiotherapy (MRgRT) offers superior soft-tissue contrast and enables adaptive treatments which improve tumor targeting and organ-at-risk sparing. However, integrated MR-Linac systems remain financially and logistically inaccessible for many hospitals. To address this gap, we implemented a modular MRgRT workflow - termed the "Virtual MR-Linac"- which decouples MR imaging and treatment delivery, enabling daily adaptive radiotherapy (ART) using diagnostic-quality MRI.
Between November 2023 and January 2025, 31 male patients with pelvic lymph node metastases were treated using this workflow. Daily MR scans were acquired in treatment position using a 1.5T MR scanner. Contours were adapted on 2D T2 turbo-spin-echo images, while synthetic CTs generated from T1 DIXON sequences were used for dose calculation. Adapted plans were delivered on a C-arm Linac using CBCT imaging for positioning. Quality assurance included independent Monte Carlo dose recalculations, automated plan parameters verification and a plan complexity check using in-house scripting.
Across 99 adapted fractions, plan adaptation improved dosimetric outcomes, with a median 14% increase in Planning Target Volume (PTV) coverage and a 7% reduction in bowel D1cc (dose to 1 cc). Median times for MR imaging, contouring, and planning were 12, 12, and 20 min, respectively.
The Virtual MR-Linac approach enables high-quality ART to compensate for inter-fractional motion without the costs and complexity of integrated systems. It improves resource utilization, maintains patient comfort, and offers a flexible, scalable solution for clinical implementation.

PMID:
42410469
Bibliographic data and abstract were imported from PubMed on 07 Jul 2026.

Read full publication at:
Please sign in to see all details.

Stats

1-terrible, 9-excellent. How would you rate this publication? Sign in in to submit your rating.

Post a comment

You need to be signed in to post comments. You can sign in here.

Comments

There are no comments yet.