White matter microstructure mapping using diffusion-only or diffusion-relaxation: protocol design and comparison of accuracy and precision

Combining diffusion and relaxation is promising in probing the tissue microstructure in brain white matter. We designed an optimal diffusion-relaxation protocol with varying b-values, b-tensor shapes and echo times by minimizing the error of parameter estimation. We compared the Standard Model parameters estimated by diffusion-relaxation and diffusion-only data using sensitivity-specificity matrices and test-retest data on volunteers and found excellent agreement. With a comprehensive acquisition protocol, the Standard Model can accurately capture the signal content in white matter with diffusion MRI.