Optimization of quasi‐diffusion magnetic resonance imaging for quantitative accuracy and time‐efficient acquisition

PURPOSE: Quasi‐diffusion MRI (QDI) is a novel quantitative technique based on the continuous time random walk model of diffusion dynamics. QDI provides estimates of the diffusion coefficient, [Formula: see text] in mm(2) s(−1) and a fractional exponent, [Formula: see text] , defining the non‐Gaussianity of the diffusion signal decay. Here, the b‐value selection for rapid clinical acquisition of QDI tensor imaging (QDTI) data is optimized. METHODS: Clinically appropriate QDTI acquisitions were optimized in healthy volunteers with respect to a multi‐b‐value reference (MbR) dataset comprising 29 diffusion‐sensitized images arrayed between [Formula: see text] and 5000 s mm(−2). The effects of varying maximum b‐value ([Formula: see text]), number of b‐value shells, and the effects of Rician noise were investigated. RESULTS: QDTI measures showed [Formula: see text] dependence, most significantly for [Formula: see text] in white matter, which monotonically decreased with higher [Formula: see text] leading to improved tissue contrast. Optimized 2 b‐value shell acquisitions showed small systematic differences in QDTI measures relative to MbR values, with overestimation of [Formula: see text] and underestimation of [Formula: see text] in white matter, and overestimation of [Formula: see text] and [Formula: see text] anisotropies in gray and white matter. Additional shells improved the accuracy, precision, and reliability of QDTI estimates with 3 and 4 shells at [Formula: see text] s mm(−2), and 4 b‐value shells at [Formula: see text] s mm(−2), providing minimal bias in [Formula: see text] and [Formula: see text] compared to the MbR. CONCLUSION: A highly detailed optimization of non‐Gaussian dMRI for in vivo brain imaging was performed. QDI provided robust parameterization of non‐Gaussian diffusion signal decay in clinically feasible imaging times with high reliability, accuracy, and precision of QDTI measures.