First-in-human technique translation of oxygen-enhanced MRI to an MR Linac system in patients with head and neck cancer

•Dynamic volumetric oxygen-enhanced MRI (OE-MRI) is well tolerated and feasible in the neck.•OE-MRI can measure oxygenation in healthy tissues in the neck.•The OE-MRI biomarker ΔR1 is highly repeatable.•The technique performs as well on an MR Linac as on a diagnostic scanner. Tumour hypoxia is prognostic in head and neck cancer (HNC), associated with poor loco-regional control, poor survival and treatment resistance. The advent of hybrid MRI – radiotherapy linear accelerator or ‘MR Linac’ systems – could permit imaging for treatment adaptation based on hypoxic status. We sought to develop oxygen-enhanced MRI (OE-MRI) in HNC and translate the technique onto an MR Linac system. MRI sequences were developed in phantoms and 15 healthy participants. Next, 14 HNC patients (with 21 primary or local nodal tumours) were evaluated. Baseline tissue longitudinal relaxation time (T1) was measured alongside the change in 1/T1 (termed ΔR1) between air and oxygen gas breathing phases. We compared results from 1.5 T diagnostic MR and MR Linac systems. Baseline T1 had excellent repeatability in phantoms, healthy participants and patients on both systems. Cohort nasal concha oxygen-induced ΔR1 significantly increased (p