Simultaneous B1 + homogenization and specific absorption rate hotspot suppression using a magnetic resonance phased...

Area of Science:

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

Background:

• High-field MRI faces challenges with B(1) (+) uniformity and specific absorption rate (SAR) deposition, impacting whole-body imaging quality.
• RF field interactions with patient anatomy, especially in obese individuals, can lead to significant B(1) (+) nonuniformity and elevated SAR levels.

Purpose of the Study:

• To investigate the potential of phased array transmit coils for simultaneous reduction of B(1) (+) nonuniformity and SAR deposition in high-field MRI.
• To assess the efficacy of generic coil settings for patient imaging, eliminating the need for pre-scan information.

Main Methods:

• Electromagnetic simulations were performed using a phased array TEM coil at 128 MHz.
• Simulations utilized two homogeneous elliptical phantoms and four dielectric patient models to mimic real-world scenarios.
• Analysis focused on B(1) (+) and electric field patterns, as well as SAR deposition.

Main Results:

• Phased array coils demonstrated a reduction in B(1) (+) nonuniformity and SAR hotspots, with SAR reduction up to 50%.
• Wave interference patterns in elliptical phantoms closely resembled those in pelvic models, highlighting anatomical influences.
• Optimized elliptical phantom settings yielded results comparable to patient-specific optimizations, suggesting generic settings are feasible.

Conclusions:

• Phased array transmit coils effectively mitigate B(1) (+) nonuniformity and reduce SAR deposition in high-field MRI.
• The possibility of using generic phase/amplitude port settings simplifies implementation and broadens applicability.
• This approach offers significant advantages for whole-body imaging at 3 Tesla, enhancing safety and image quality.