Correcting the unwanted diffusion-weighting in STEAM-DWI Sequence for Time-Dependent Diffusional Kurtosis Imaging

Motivation: Time-dependent diffusion kurtosis imaging (tDKI) enables the noninvasive mapping of transmembrane water exchange by measuring diffusion signals at varying diffusion-times. To access long diffusion-times, the diffusion-weighted STEAM sequence is typically used, in which the unwanted diffusion weighting produced by the crushers and slice selection gradients. Goal(s): We first showed that this unwanted weighting, particularly on the b0 image led to an underestimation of kurtosis. Approach: We proposed a strategy to resolve this problem by removing the crusher gradient while adding a smaller and fixed b value to the b0 acquisition. Results: Proposed strategy showed reasonable tDKI measurements in phantom and human brain experiments. Impact: This study presented an important issue of unwanted diffusion-weighting in STEAM-DWI, which led to inaccurate estimation of tDKI-based transmembrane water exchange. We proposed a strategy that removed the crusher and dynamically adjusting the diffusion gradient to achieve the desired b-value.