Multi-center diffusion-weighted MRI validation for 0.35T MR-Linac
Recommended Citation
Nejad-Davarani S, Lutsik N, Mittauer K, Bassiri-Gharb N, Weygand J, Armstrong T, Pokharel S, Rana S, Wang H, Gutierrez A, Kasper M, and Mellon E. Multi-center diffusion-weighted MRI validation for 0.35T MR-Linac. Phys Med 2026;142:105726.
Document Type
Article
Publication Date
2-1-2026
Publication Title
Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB)
Keywords
Diffusion Magnetic Resonance Imaging, Reproducibility of Results, Phantoms, Imaging, Humans, Particle Accelerators, Echo-Planar Imaging
Abstract
BACKGROUND: MR-linac (MRL)-based radiotherapy allows daily anatomical and physiological imaging for adaptive treatment. Apparent diffusion coefficient (ADC) derived from diffusion-weighted imaging (DWI) is a quantitative biomarker correlated with tumor cellularity and response. Verifying ADC repeatability and reproducibility across centers is key for multi-center physiological adaptive radiotherapy trials on low-field MRLs.
METHODS: Echo-planar imaging (EPI)-based DWI was performed on a commercial phantom containing 13 0-50% polyvinylpyrrolidone (PVP) vials. Diffusion weighting was applied in three orthogonal directions using two b-value sets: [0,30,60,90,120,150,180,200,500,1000] and [0,500,1000] s/mm(2). Reproducibility was assessed across four institutions using brain and torso coils. Repeatability was evaluated with four scans at one site. To assess gantry angle effects, scans were repeated at the angle inducing highest distortion. Coefficient of variation (COV) and normalized deviation from reference ADC values were calculated.
RESULTS: Using three b-values, COVs on a single MRL ranged 0.339-2.914% (brain coil) and 0.466-6.902% (torso coil); and with ten b-values, ranged 0.196-3.679% and 0.408-6.699%, respectively. Multi-site COVs ranged 0.329-3.413% (three b-values) and 0.499-2.420% (ten b-values) using brain coil, and 0.267-4.442% and 0.381-5.357% with torso coil. At zero-degree gantry angle, normalized root mean squared error (nRMSE) ranged 2.857-3.538% (single MRL) and 3.015-3.952% (multi-center). Distortion increased nRMSE to 10.767% and 6.236% with three and ten b-values, respectively.
SIGNIFICANCE: These findings demonstrate excellent repeatability and reproducibility of ADC values on low-field MRLs across coils and b-value sets, supporting its use as a reliable biomarker in multi-center adaptive radiotherapy trials.
Medical Subject Headings
Diffusion Magnetic Resonance Imaging; Reproducibility of Results; Phantoms, Imaging; Humans; Particle Accelerators; Echo-Planar Imaging
PubMed ID
41558339
Volume
142
First Page
105726
Last Page
105726
