A geometrically decoupled, twisted solenoid single-axis gradient coil set for TRASE

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Radiofrequency (RF) Coil Design
• Biophysics

Background:

• Transverse Resonance Acquisition and Shimming Encoding (TRASE) utilizes phase gradients in RF fields for MRI data encoding.
• Twisted solenoid coils offer efficient TRASE imaging for transverse geometries.
• Combining two such coils can enhance k-space coverage and spatial resolution, but inductive coupling is a challenge.

Purpose of the Study:

• To demonstrate geometric decoupling of two concentric twisted solenoid RF coils for TRASE.
• To overcome the strong inductive coupling between coaxial twisted solenoids.
• To improve k-space coverage and spatial resolution in TRASE imaging.

Main Methods:

• Designed two concentric twisted solenoids using Biot-Savart calculations.
• Incorporated regular solenoids in series with each twisted solenoid to minimize mutual inductance.
• Utilized FastHenry2 simulations to determine optimal regular solenoid geometry.
• Assessed TRASE encoding performance through simulations and experimental validation.

Main Results:

• Achieved good isolation (X dB) between the coil pair with minimal magnitude (3.7%) and phase distortions.
• Confirmed doubled k-space coverage in TRASE experiments.
• Acquired 128 k-space points within 80 ms, enabling rapid imaging of short T2 samples.

Conclusions:

• Successfully demonstrated geometric decoupling of twisted solenoid phase gradient RF coils.
• The proposed method offers advantages over active decoupling, including faster switching and reduced hardware complexity.
• This technique is scalable and enhances TRASE imaging capabilities.