Time-Efficient Interleaved Spin Density-Weighted and Inversion Recovery ²³Na MRI of the Human Calf Muscle at 7 T

Area of Science:

• Magnetic Resonance Imaging
• Biomedical Engineering
• Medical Physics

Background:

• Sodium-23 (²³Na) MRI provides valuable insights into tissue physiology.
• Spin density-weighted (SDW) and inversion recovery (IR) contrasts offer complementary information.
• Acquiring both SDW and IR ²³Na MRI contrasts typically requires separate measurements, increasing scan time.

Purpose of the Study:

• To develop a time-efficient ²³Na MRI sequence capable of acquiring both SDW and IR contrasts simultaneously.
• To eliminate the need for additional measurement time for acquiring complementary ²³Na MRI contrasts.

Main Methods:

• A novel pulse sequence was designed by dividing the conventional 180° inversion pulse into two 90° pulses with an inserted readout.
• The sequence was evaluated using simulations and phantom measurements.
• The sequence's feasibility and signal characteristics were assessed in vivo using calf muscle MRI in healthy volunteers at 7 Tesla.

Main Results:

• The interleaved SDW/IR sequence achieved image quality and contrast comparable to standard SDW and IR sequences.
• Phantom experiments showed minor changes in contrast due to slightly increased T1-weighting.
• In vivo calf muscle measurements demonstrated no significant differences in mean muscle signal compared to standard sequences.

Conclusions:

• The proposed interleaved sequence enables simultaneous acquisition of ²³Na SDW and IR contrasts.
• This approach effectively reduces overall MRI scan time.
• Eliminating the need for co-registration simplifies the imaging protocol.