Sodium long-component T(2)(*) mapping in human brain at 7 Tesla

Area of Science:

• Neuroimaging
• Magnetic Resonance Imaging (MRI)
• Biophysics

Background:

• Sodium (23Na) MRI offers unique insights into brain cellular and metabolic health.
• Accurate quantification of tissue sodium concentration from (23)Na MRI requires understanding tissue-specific parameters like transverse relaxation times (T(2)).

Purpose of the Study:

• To report the long component of effective transverse relaxation time T(2)* values for sodium ((23)Na) in various brain regions.
• To establish a foundation for precise sodium concentration quantification in (23)Na MRI with non-zero echo times.

Main Methods:

• Utilized a two-point gradient-echo sequence at 7 Tesla.
• Employed optimized parameters (TE1=12ms, TE2=37ms, N1=5, N2=15, TR=130ms) for efficient data acquisition.
• Acquired data from six healthy volunteers.

Main Results:

• The long T(2)* component of tissue sodium varied across brain regions: cerebrospinal fluid (54±4 ms), gray matter (28±2 ms), and white matter (29±2 ms).
• Observed an increase in the long T(2)* component with increasing static magnetic field strength (B(0)).

Conclusions:

• The determined T(2)* values are essential for accurate sodium quantification in (23)Na MRI.
• These findings will inform the development of advanced MRI techniques, such as triple-quantum imaging.
• The results hold potential for clinical utility in assessing brain tissue integrity.