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Feasibility of submillimeter functional quantitative susceptibility mapping using 3D echo planar imaging at 7 T
Sina Straub1, Xiangzhi Zhou1, Shengzhen Tao1
1Department of Radiology, Mayo Clinic, Jacksonville, Florida, USA.
NMR in Biomedicine
|October 14, 2024
Summary
Submillimeter functional quantitative susceptibility mapping (fQSM) offers improved brain activation localization compared to traditional BOLD fMRI. This advanced technique provides higher precision in mapping neural activity within the cortex.
Area of Science:
- Neuroimaging
- Biophysics
- Magnetic Resonance Imaging
Background:
- Quantitative susceptibility mapping (QSM) is a neuroimaging technique for mapping tissue magnetic susceptibility.
- Blood-oxygen-level-dependent (BOLD) signals in functional MRI (fMRI) reflect changes in blood oxygenation.
- Directly quantifying susceptibility changes offers a complementary approach to BOLD fMRI for functional brain mapping.
Purpose of the Study:
- To present and evaluate a submillimeter functional QSM (fQSM) approach.
- To compare the performance of fQSM against traditional BOLD fMRI using ultra-high field 3D gradient-echo echo planar imaging (EPI).
- To assess the feasibility of whole-brain fQSM at submillimeter resolution.
Main Methods:
- Acquisition of complex EPI data in nine healthy subjects at varying resolutions.
- Application of fQSM using 3D path-based unwrapping, sophisticated harmonic artifact reduction for phase data, and streaking artifact reduction for QSM.
- Functional data analysis using general linear modeling and computation of z-scores, with denoising via NOise reduction with DIstribution Corrected (NORDIC).
- Inclusion of motor tasks (finger tapping) and intentional motion experiments.
Main Results:
- fQSM demonstrated an expected decrease in magnetic susceptibility correlating with BOLD signal increases in sensorimotor areas.
- fQSM consistently showed smaller activation regions compared to BOLD fMRI.
- A higher percentage of significant negative t-values (52%) were localized in the cortex using fQSM versus fMRI (45%).
- Paradigm-dependent signal evolution was recoverable even with intentional motion exceeding voxel size, following motion correction.
Conclusions:
- Submillimeter whole-brain fQSM is feasible with a voxel volume of 0.53 μL.
- fQSM offers improved localization of brain activation within the cortex compared to traditional BOLD fMRI.
- The findings highlight fQSM's potential for high-resolution functional neuroimaging, particularly with submillimeter 3D EPI sequences.
