Empirical Reproducibility, Sensitivity, and Optimization of Acquisition Protocol for Neurite Orientation Dispersion and Density Imaging using AMICO
Prasanna Parvathaneni, Vishwesh Nath, Justin A. Blaber, Kurt G Schilling, Allison E. Hainline, Adam W Anderson, and Bennett A. Landman “Empirical Reproducibility, Sensitivity, and Optimization of Acquisition Protocol for Neurite Orientation Dispersion and Density Imaging using AMICO”. Magnetic Resonance Imaging. Mar 2018.
Neurite Orientation Dispersion and Density Imaging (NODDI) is a relatively new model for diffusion weighted magnetic resonance imaging (MRI) that has been gaining prominence for estimating multiple diffusion compartments from MRI data acquired in a clinically feasible time. To establish a pathway for adoption of NODDI in clinical studies, it is important to understand the sensitivity and reproducibility of NODDI metrics on empirical data in the context of acquisition protocol and brain anatomy. Previous studies addressed reproducibility across the 3T scanners and within session and between subject reproducibility at 1.5T and 3T. However, empirical reproducibility on the performance of NODDI metrics based on b-value and diffusion-sensitized directions has not yet been addressed. In this study, we investigate a high angular resolution dataset with 11 repeats of a study with five b-values shells (1000, 1500, 2000, 2500 and 3000 s/mm2) and 96 directions per shell on a single subject. The NODDI model was estimated using Accelerated Microstructure Imaging via Convex Optimization (AMICO) for different b-values and gradient directions on two-shell HARDI data fixing the lower shell at b=1000s/mm2. The gold standard was defined as the NODDI model applied to all acquired imaging data, which was used as a baseline to compare the performance of metrics by acquisition protocol based on the white matter regions. Additionally, we characterize ODI reproducibility using single-shell data across all b-values for different gradient directions. The experimental findings confirmed the sensitivity of intracellular volume fraction (Vic) with the choice of outer shell b-value more than with the choice of gradient directions. Orientation dispersion index (ODI), on the other hand is more sensitive to the number of gradient directions compared to b-value selection. Single-shell results for ODI are more comparable to 2-shell data at lower b-values than higher b-values. Recommended settings by region of interest and acquisition time are reported for the researchers considering using NODDI in human studies and/or comparing results across acquisition protocols.
Keywords: NODDI, AMICO, Microstructure imaging, Reproducibility, Advanced DW-MRI