Related Experiment Video
Updated: Sep 10, 2025
High-resolution Functional Magnetic Resonance Imaging Methods for Human Midbrain
Published on: May 10, 2012
Mapping Regional Brain Total Sodium Concentration Using Anatomically Guided Reconstruction of Dual-Echo Sodium-23
Alaleh Alivar1,2, Georg Schramm3, Yongxian Qian1,2
1From the Department of Radiology (A.A., Y.Q., H.L., Y.W.L.), Bernard and Irene Schwartz Center for Biomedical Imaging, New York University Grossman School of Medicine, New York, New York.
Background And Purpose:
Sodium (23Na) MRI provides unique information about ionic homeostasis in the brain. However, in vivo quantification of regional brain sodium is highly challenging due to low SNR and limited spatial resolution. Here, we use our novel anatomically guided reconstruction (AGR) method to overcome these challenges and enable precise quantification of regional brain total sodium concentration (TSC).
Materials And Methods:
Thirty-four healthy subjects were studied by using a 3T clinical MRI scanner with a dual-tuned (1H-23Na) birdcage coil. 23Na images were acquired by using a twisted projection imaging sequence (TR = 100 ms, TE1/TE2 = 0.5/5 ms), while proton (1H) images were obtained with a standard T1-weighted MPRAGE sequence. AGR was performed with regularization parameters βr = 0.67, 2.0, and 6.0. As a baseline comparison, standard reconstruction (SR) was also performed by using a regridding algorithm with compensation for nonuniform sampling. To assess partial volume effects (PVEs) on the reconstruction methods, an erosion experiment was conducted. Internal linear calibration using noise-only background and vitreous humor regions was applied to calculate TSC in ROIs including lobar cortical GM, subcortical (including hippocampus, caudate, pallidum, putamen and thalamus), callosal, and whole-brain WM. Bonferroni-corrected pair-wise comparison was performed by using Multivariate Analysis of Variance at a significance level P < .05.
Results:
The WM erosion experiments confirmed that TSCAGR was stabilized beyond 1-voxel erosion in the WM, but TSCSR was decreasing with erosion increasing, showing a reduced PVE in the AGR images. AGR also shows greater separation in TSC between GM and WM compared with SR (GM TSCSR = 49.2 ± 4.6 mmol/L, WM TSCSR = 38.1 ± 3.0 mmol/L; GM TSCAGR = 48.6 ± 4.9 mmol/L, WM TSCAGR = 30.5 ± 2.8 mmol/L). We also found smaller variance of TSCAGR in WM and GMsubcortical compared with TSCSR.
Conclusions:
The AGR helps sodium quantification in healthy human brains by reducing the PVE and variance of TSC in noncortical brain regions. Our normative values of TSC in the brain regions set the stage to better understand derangements of 23Na metabolism and homeostasis in neurologic disease.
