Prospective evaluation of in vivo and phantom repeatability and reproducibility of diffusion-weighted MRI sequences on 1.5 T MRI-linear accelerator (MR-Linac) and MR simulator devices for head and neck cancers

•Repeatability and reproducibility of MR-linac DWI sequences were within 2.22% and 4.37% of MR sim DWI sequences, respectively.•Of the MR-linac DWI sequences, SPLICE generally outperformed EPI and TSE in terms of repeatability/reproducibility, ADC bias, and SNR.•Spatial dependence of phantom ADC values was observed for the MR-linac but not for the MR sim, which may be due to uncorrected gradient non-linearities.•MR-linac DWI sequences are robust and worthy of further clinical evaluation for treatment response assessment and biological image-guided ART in HNC.