Toward imaging the body at 10.5 tesla

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Biomedical Engineering
• Radiofrequency Engineering

Background:

• Advancements in MRI technology aim to improve image quality and diagnostic capabilities.
• Higher magnetic field strengths (e.g., 7.0T and above) offer theoretical SNR benefits but present significant technical challenges.
• Evaluating radiofrequency (RF) performance is crucial for translating high-field MRI to clinical applications, particularly for body imaging.

Purpose of the Study:

• To compare the transmit/receive performance of dipole antenna arrays at 10.5 Tesla (T) versus 7.0T for body imaging.
• To assess the feasibility of 10.5T MRI for anatomical regions including the prostate, kidneys, and heart.
• To evaluate signal-to-noise ratio (SNR) gains and specific absorption rate (SAR) at 10.5T.

Main Methods:

• Designed and simulated fractionated dipole antenna elements for 10.5T body imaging.
• Investigated transmit performance using phase-only RF shimming and multi-spoke pulses at 10.5T and 7.0T.
• Constructed a 10-channel antenna array for swine abdomen imaging at 10.5T and validated numerical methods with phantom studies.

Main Results:

• Similar power efficiencies were observed at 10.5T and 7.0T with phase-only shimming, but RF nonuniformity increased significantly at 10.5T.
• Multi-spoke RF pulses yielded comparable transmit performance with 25-90% higher local SAR at 10.5T versus 7.0T.
• Relative SNR gains exceeded two-fold at 10.5T within target organs, with a measured 2.2-fold gain in a phantom. Gradient echo and fast spin echo imaging demonstrated feasibility.

Conclusions:

• Dipole antenna arrays with static shimming can achieve comparable power efficiencies at 10.5T, but increased RF nonuniformities necessitate advanced parallel transmission techniques.
• The study demonstrates the potential for 10.5T body MRI, highlighting the need for robust RF shimming and transmission strategies.
• Further research into efficient and safe parallel transmission methods is essential for realizing the full benefits of 10.5T MRI.