High-resolution quantitative sodium imaging at 9.4 Tesla.

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Neuroimaging
• Biophysics

Background:

• Accurate measurement of sodium concentration in the human brain is crucial for understanding neurological function and disease.
• Traditional MRI methods face limitations in achieving the resolution necessary to minimize partial volume effects in brain tissue.
• Ultrahigh field strength MRI offers potential for enhanced sensitivity and resolution.

Purpose of the Study:

• To investigate the feasibility of performing high-resolution quantitative sodium imaging at 9.4 Tesla (T).
• To assess the capability of ultrahigh field MRI to reduce partial volume effects for precise sodium concentration measurements.
• To evaluate the sensitivity and signal-to-noise ratio achievable with this technique.

Main Methods:

• Development of a dual-tuned proton/sodium coil system combining a birdcage coil with a proton patch antenna.
• Acquisition of sodium density-weighted images using an ultrashort echo time sequence at 1x1x5 mm(3) nominal resolution within 30 minutes.
• Implementation and verification of signal calibration, B0, B1, and off-resonance correction methods on phantoms and human volunteers.

Main Results:

• Achieved an actual voxel volume of approximately 40 μL at 9.4T with acceptable signal-to-noise ratios (8 for brain tissue, 35 for CSF).
• Measured mean sodium concentrations in gray matter (36 ± 2 mmol/L) and white matter (31 ± 1 mmol/L) comparable to literature values.
• Demonstrated the effectiveness of correction methods for quantitative accuracy.

Conclusions:

• High-resolution quantitative sodium imaging at 9.4T is feasible and provides a viable tool for accurate brain sodium concentration measurement.
• Ultrahigh field strength significantly enhances sensitivity, enabling the reduction of partial volume effects crucial for precise quantification.
• This technique holds promise for advancing the understanding of brain physiology and pathology.