Evaluation of multi-shell diffusion MRI acquisition strategy on quantitative analysis using multi-compartment models.

Area of Science:

• Neuroimaging
• Biomedical Engineering
• Radiology

Background:

• Advanced diffusion MRI (dMRI) models like Neurite Orientation Dispersion and Density Imaging (NODDI) are crucial for biomedical research.
• Current NODDI models often require lengthy multi-shell acquisitions, limiting use in uncooperative patients (e.g., infants).
• There's a need for versatile dMRI protocols that allow analysis with multiple models for comprehensive data interpretation.

Purpose of the Study:

• To develop and evaluate a fast, multi-shell dMRI acquisition strategy.
• To enable simultaneous application of NODDI and diffusion basic spectrum imaging (DBSI) models on a single dataset.
• To assess the feasibility of this approach in a clinical 3T setting using macaque monkeys.

Main Methods:

• Explored multiple gradient-encoding schemes with 4-6 shells and moderate b-values (up to 2,000 s/mm²).
• Acquisition times ranged from 3 to 8 minutes for a single scan.
• Tested protocols on macaque monkeys and analyzed data using NODDI and DBSI models.

Main Results:

• Orientation dispersion index (ODI) and CSF maps were consistent across various shell schemes.
• Intra-cellular volume fraction (ICVF) maps showed reduced detail with fewer directions or lower b-values.
• Hindered diffusion and CSF ratio maps were comparable; restricted diffusion ratio maps showed comparable results between 80 and 32 directions at b=2,000 s/mm².

Conclusions:

• A fast multi-shell dMRI acquisition and processing strategy was developed, allowing complementary insights from NODDI and DBSI models.
• This approach facilitates the characterization of microstructural alterations and inflammation from a single dMRI scan.
• The method is particularly promising for neurodegenerative disorders and acute stroke patients, especially those unable to cooperate during scans.