Orthogonalizing crusher and diffusion-encoding gradients to suppress undesired echo pathways in the twice-refocused...

Area of Science:

• Magnetic Resonance Imaging
• Diffusion Imaging

Background:

• The twice-refocused spin echo sequence is crucial for diffusion imaging, effectively reducing eddy currents.
• This sequence involves three radiofrequency pulses, resulting in eight signal pathways.
• Existing methods for crusher and diffusion gradients lack a universal solution for all b-values and directions.

Purpose of the Study:

• To introduce and validate a novel solution for crusher gradients in diffusion imaging.
• To ensure the independence of crusher and diffusion-encoding gradients by maintaining orthogonality.
• To address limitations in current gradient design for arbitrary diffusion-sensitizing parameters.

Main Methods:

• Demonstrated the cancellation effect between crusher and diffusion gradients.
• Implemented crusher gradients orthogonal to diffusion gradients.
• Conducted phantom and in-vivo experiments to assess image quality and artifact reduction.

Main Results:

• Artifactual signal modulation was observed when crusher and diffusion gradients were not independent.
• Implementing orthogonal gradients successfully eliminated artifacts.
• Orthogonal crusher gradients did not negatively impact image quality.

Conclusions:

• Orthogonal crusher gradients offer a simple and effective solution for diffusion imaging.
• This method is compatible with various diffusion imaging sequences, including diffusion tensor imaging and fiber diameter mapping.
• Applicable to any diffusion imaging sequence utilizing the twice-refocused spin echo scheme.