Radial TRASE: 2D RF encoding through mechanical rotation and active digital decoupling.

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Radiofrequency (RF) Coil Technology
• Image Encoding Techniques

Background:

• Traditional 2D transmit array spatial encoding (TRASE) utilizes four radiofrequency fields, presenting challenges due to element interactions.
• Simplified transmit (Tx) arrays are desirable for improving 2D imaging efficiency and reducing complexity.

Purpose of the Study:

• To present a novel, low-cost, 2D radial encoding scheme (Radial TRASE) using a simplified two-coil array.
• To overcome the limitations of previous multi-coil TRASE methods in 2D imaging.

Main Methods:

• A two-coil B1 phase gradient system was developed for transverse encoding.
• Mechanical rotation of the transmit array enabled radial k-space acquisition.
• Active digital decoupling was employed to enhance coil isolation and mitigate residual coupling.
• Experimental verification was performed on a 2-MHz Halbach magnet with a static B0 slice-selection gradient.

Main Results:

• Radial TRASE achieved image resolutions better than 1.67 mm in water phantoms.
• The simplified two-coil array demonstrated minimal image distortions.
• Active digital decoupling reduced residual coupling to -50 dB, significantly improving isolation.
• Sequential axial slice imaging was successfully demonstrated.

Conclusions:

• Two-coil Radial TRASE enables 2D slice encoding without the need for rapidly switched B0 gradients.
• This simplified design significantly reduces the complexity of the transmit array and improves isolation compared to previous Cartesian TRASE methods.