High-resolution MRI encoding using radiofrequency phase gradients.

Area of Science:

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

Background:

• Conventional MRI relies on expensive and complex magnetic field gradients for image encoding.
• These gradients contribute to acoustic noise and potential nerve stimulation, limiting patient comfort and access.
• Global access to MRI is restricted compared to other imaging modalities like X-ray or ultrasound.

Purpose of the Study:

• To introduce and evaluate a novel MRI encoding principle, Transmit Array Spatial Encoding (TRASE).
• To demonstrate TRASE's capability to generate high-resolution images without conventional B0 field gradients.
• To explore the potential of TRASE for cost-effective and advanced MRI applications.

Main Methods:

• TRASE utilizes resonant radiofrequency (RF) fields for Fourier spatial encoding, replacing B0 gradients.
• A transmit coil array with a single transmitter channel generated phase gradient fields for encoding two spatial axes.
• Spin refocusing with phase gradient transmit fields in spin echo trains facilitated k-space traversal.
• High-resolution 2D in vivo MR images of hand and wrist were acquired at 0.2 T.

Main Results:

• TRASE successfully produced high-resolution 2D in vivo MR images without B0 field gradients.
• The method demonstrated Fourier spatial encoding solely through RF field manipulation.
• Acquired images of hand and wrist at 0.2 T validated the TRASE principle.
• TRASE showed potential for low-cost diagnostics and unique imaging capabilities.

Conclusions:

• TRASE offers a viable alternative to conventional MRI encoding, potentially reducing costs and complexity.
• This technique opens possibilities for novel MRI experiments and applications, particularly in lower field strengths (<1 T) and micro-imaging.
• TRASE is compatible with existing B0 gradient encoding and parallel imaging, allowing for hybrid sequences.