Comparison of time-division multiplexing and multi-echo sequences for accelerated relaxation diffusion MRI

Motivation: Compare multi-echo and time-division multiplexing (TDM) sequences that accelerate multi-TE dMRI scans. Goal(s): To investigate the accuracy of multi-TE diffusion measures using multi-echo and TDM sequences. Approach: Standard single-TE spin-echo echo-planar imaging (EPI), dual-echo EPI, and TDM-EPI sequences were implemented using Pulseq with matched diffusion and readout gradients. A calibration phantom and a human subject were scanned on two scanners to examine the accuracy of R2 (1/T2) and apparent diffusivity coefficient (ADC) maps. Results: TDM demonstrates up to 160% reduction in estimated R2 on phantom and 30% in in-vivo data compared to dual-echo sequence. Impact: The proposed TDM sequence allows for fast and accurate T2 and ADC estimation compared to the conventional multi-echo sequence, making it a potential tool for relaxation-diffusion imaging.