MR gradient response modeling to ensure excitation coherence

Area of Science:

• Magnetic Resonance Imaging (MRI) Physics
• Signal Processing
• Medical Imaging Technology

Background:

• Gradient system response significantly impacts k-space trajectory shape and dispersion in techniques like echo-planar imaging.
• Accurate characterization of gradient response is crucial for precise magnetic resonance imaging (MRI) and designed excitation.

Purpose of the Study:

• To develop and present a novel method for directly characterizing gradient system response in MRI.
• To delineate k-space trajectories and assess factors like magnetic field homogeneity and RF/gradient waveform coherence.

Main Methods:

• Developed a method placing k-space 'landmarks' directly within raw MRI data.
• Modeled gradient response as a linear system with a frequency-dependent delay function.
• Collected data under varying conditions to derive model parameters.

Main Results:

• The method clearly delineates k-space trajectories.
• It provides information on magnetic field homogeneity and temporal coherence of RF and gradient waveforms.
• A linear system model of gradient response was established.

Conclusions:

• The developed method enables direct characterization of gradient system response.
• Derived parameters allow for corrections to RF waveforms or k-space trajectories.
• Demonstrated successful application of corrections to designed excitation with sinusoidal k-space trajectories.