Quantitative magnetic resonance imaging on hybrid magnetic resonance linear accelerators: Perspective on technical and clinical validation

Abstract

Many preclinical and clinical observations support that functional magnetic resonance imaging (MRI), such as diffusion weighted (DW) and dynamic contrast enhanced (DCE) MRI, might have a predictive value for radiotherapy. The aim of this review was to assess the current status of quantitative MRI on hybrid MR-Linacs. In a literature research, four publications were identified, investigating technical feasibility, accuracy, repeatability and reproducibility of DW and DCE-MRI in phantoms and first patients. Accuracy and short term repeatability was < 5% for DW-MRI in current MR-Linac systems. Consequently, quantitative imaging providing accurate and reproducible functional information seems possible in MR-Linacs.

Initial Feasibility and Clinical Implementation of Daily MR-Guided Adaptive Head and Neck Cancer Radiation Therapy on a 1.5T MR-Linac System: Prospective R-IDEAL 2a/2b Systematic Clinical Evaluation of Technical Innovation

“…Furthermore, first technical studies have shown that MR imaging using the 1.5 T Unity system not only provides excellent anatomic image data 40,41 but also allows for robust and reproducible quantitative imaging techniques, such as diffusion-weighted imaging. [40][41][42][43] Consequently, functional MR data acquired sequentially during MR-guided RT needs to be investigated systematically to pave the way toward future biologically individualized RT of HNC. Next steps include an R-IDEAL stage 2a evaluation of functional imaging integration and feasibility with diffusion-weighted imaging and stage 2a implementation using an ART reduco 14 approach within the prospective phase 2 randomized MR-ADAPTOR trial.…”

Technical Challenges of Real-Time Adaptive MR-Guided Radiotherapy

“…Consequently, interventions steered by functional MR imaging biomarkers seem to be one of the most promising concepts towards personalized, biologically individualized RT. Even though prognostic information using functional MR imaging may also be gathered with state-of-the-art diagnostic MR systems which do not suffer from hardware limitations such as the hybrid MR-linac scanners ( 74 ), biological real-time adaptation such as image biomarker guided dose painting to overcome local tumor radiation resistances can only be realized on hybrid MR-linacs ( 75 ). Biological RT individualization in terms of dose adaptation based on imaging information requires the measurement of quantitative imaging biomarkers ( 76 ).…”

Delta Radiomics Analysis for Local Control Prediction in Pancreatic Cancer Patients Treated Using Magnetic Resonance Guided Radiotherapy

“…Models able to provide reliable predictions during the RT course can be of great value to clinicians, allowing timely change of the dose prescription, moving towards dose escalation, or alternative approaches for patients indicated by the model as not-responders, in the perspective of response-based treatment adaptation [ 42 ].…”