Repeatability, Distortion and SNR comparison of diffusion-weighted imaging techniques on an MR-Linac

DW-acquisitions with high ADC accuracy, precision and low geometric distortion are necessary for using ADC maps for treatment planning and response assessment in MR-guided radiotherapy on MR-Linacs. We measured SNR, ADC bias, repeatability coefficient and marker distances on the NIST phantom for DW-EPI, DW-TSE and SPLICE protocols. Two volunteers were scanned in the head and neck region. The investigated TSE-based protocols showed ADC bias and DW-EPI demonstrated better repeatability. Spectral fat-suppression techniques led to higher SNR than using STIR. SPLICE DWI could be an alternative to diffusion EPI with reduced distortion and comparable SNR, if low-high profile order is used.