Triple-quantum-filtered sodium imaging at 9.4 Tesla.

Area of Science:

• Magnetic Resonance Imaging
• Biophysics
• Medical Physics

Background:

• Ultra-high field (UHF) magnetic resonance imaging (MRI) offers enhanced sensitivity.
• Triple-quantum-filtered (TQF) sodium imaging is valuable for assessing tissue viability.
• Acquiring high-quality TQF sodium images at UHF presents technical challenges.

Purpose of the Study:

• To develop an efficient method for acquiring TQF sodium images at 9.4 Tesla (UHF).
• To optimize TQF preparation pulse parameters for improved signal-to-noise ratio (SNR) and reduced specific absorption rate (SAR).

Main Methods:

• Utilized a three-pulse preparation sequence combined with a stack of double-spirals acquisition at 9.4T.
• Implemented flip angle apodization during TQ preparation to reduce SAR while preserving central k-space signal.
• Validated the method using simulations, phantom studies, and in vivo measurements.

Main Results:

• Achieved approximately 20% higher sensitivity compared to standard TQF acquisition without apodization.
• Successfully suppressed signals from free sodium ions.
• Acquired B0-corrected in vivo TQF sodium images (5x5x5 mm3 resolution) with acceptable SNR in 21 minutes.

Conclusions:

• The proposed flip angle apodization technique enhances the efficiency of TQF sodium imaging at UHF (9.4T).
• This method allows for more effective utilization of the increased sensitivity provided by UHF MRI.
• The developed approach facilitates in vivo sodium MRI with improved quality and acquisition time.