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Updated: Jan 10, 2026
Co-analysis of Brain Structure and Function using fMRI and Diffusion-weighted Imaging
Published on: November 8, 2012
Assessment of precision and accuracy of brain white matter microstructure using combined diffusion MRI and
Santiago Coelho1,2, Ying Liao1,2, Filip Szczepankiewicz3
1Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine, New York, New York, USA.
Abstract:
Joint modeling of diffusion and relaxation has seen growing interest due to its potential to provide complementary information about tissue microstructure. For brain white matter (WM), we designed an optimal diffusion-relaxometry MRI protocol that samples multiple b-values, B-tensor shapes, and echo times (TE). This variable-TE protocol (27 min) has as subsets a fixed-TE protocol (15 min) and a two-shell dMRI protocol (7 min), both characterizing diffusion only. We assessed the sensitivity, specificity, and reproducibility of these protocols with synthetic experiments and in six healthy volunteers. Compared with the fixed-TE protocol, the variable-TE protocol enables estimation of the free water fraction while also capturing compartmental relaxation times. Jointly measuring diffusion and relaxation offers increased sensitivity and specificity to microstructure parameters in brain WM with voxelwise coefficients of variation below 10%.
Insights
This study introduces an advanced MRI protocol for brain white matter, improving tissue microstructure analysis by combining diffusion and relaxation measurements. The new method offers enhanced sensitivity and specificity for detailed imaging.
Area of Science:
- Magnetic Resonance Imaging (MRI)
- Biophysics
- Neuroimaging
Background:
- Diffusion MRI (dMRI) and relaxometry provide complementary information on tissue microstructure.
- Joint modeling of diffusion and relaxation is gaining interest for comprehensive tissue characterization.
- Brain white matter (WM) microstructure is complex and benefits from advanced imaging techniques.
Purpose of the Study:
- To design and evaluate an optimal diffusion-relaxometry MRI protocol for brain white matter.
- To assess the sensitivity, specificity, and reproducibility of the proposed protocol.
- To compare the performance of a variable echo time (TE) protocol against fixed-TE and diffusion-only protocols.
Main Methods:
- Development of a variable-TE MRI protocol sampling multiple b-values and B-tensor shapes.
- Inclusion of subsets for fixed-TE and two-shell dMRI protocols within the variable-TE framework.
- Validation using synthetic data and experiments in six healthy volunteers.
Main Results:
- The variable-TE protocol (27 min) captures both diffusion and T2 relaxation, unlike shorter diffusion-only protocols.
- It enables estimation of the free water fraction and compartmental T2 relaxation times.
- Joint diffusion-relaxation measurements improved sensitivity and specificity for WM microstructure parameters.
Conclusions:
- The designed variable-TE diffusion-relaxometry MRI protocol enhances the characterization of brain white matter microstructure.
- This approach provides complementary information beyond diffusion-only methods.
- The protocol demonstrates high sensitivity, specificity, and reproducibility with voxelwise coefficients of variation below 10%.
