Simultaneously driven linear and nonlinear spatial encoding fields in MRI.

Area of Science:

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

Background:

• Conventional MRI spatial encoding relies on linear magnetic fields.
• The Parallel Imaging Technique using Localized Gradients (PatLoc) utilizes nonlinear fields.
• Nonlinear fields may improve gradient performance and reduce nerve stimulation.

Purpose of the Study:

• To investigate the feasibility of using nonlinear fields for spatial encoding in MRI.
• To develop and evaluate multidimensional encoding strategies with combined linear and nonlinear gradients.
• To compare different gradient-encoding strategies through simulations and experiments.

Main Methods:

• A custom insert coil generating two quadratic encoding fields was used.
• High-performance amplifiers drove the coil within a clinical MR system.
• Simulations and experiments compared six gradient-encoding strategies, including Cartesian and radial-based trajectories.

Main Results:

• The combined hardware enabled independent manipulation of five spatial encoding fields.
• Multidimensional encoding using both linear and nonlinear fields was practically achieved.
• A novel radial-based trajectory demonstrated PatLoc's variable spatial resolution capability.

Conclusions:

• Nonlinear spatial encoding using PatLoc is feasible and offers advantages over conventional linear methods.
• The developed multidimensional encoding strategies are practically achievable.
• The new radial-based trajectory provides variable spatial resolution across the field-of-view.