Experiments for two MR imaging theories of motion phase sensitivity

Area of Science:

• Medical Imaging
• Physics
• Biomedical Engineering

Background:

• Motion artifacts in Magnetic Resonance (MR) imaging arise from motion-sensitive phase shifts.
• Discrepancies exist between two theories predicting these motion-induced artifacts.
• Accurate gradient waveform design is crucial for minimizing motion contamination in MR imaging.

Purpose of the Study:

• To resolve the discrepancy between two theories of motion-sensitive phase shifts in MR imaging.
• To evaluate the effectiveness of different gradient waveform compensation strategies.
• To identify optimal methods for minimizing motion artifacts in MR imaging.

Main Methods:

• Computer integration of fundamental Bloch equations for MR imaging with motion.
• Simulation of constant and erratic motion using a monopolar gradient waveform test case.
• Comparison of transport integral solutions with conventional method-of-moments gradient moment nulling.

Main Results:

• Simulation images showed strong agreement with transport integral solutions for motion phase sensitivity.
• Artifacts were identified as time-of-flight oblique flow misregistration.
• Conventional gradient moment nulling increased motion artifacts compared to no compensation; second-integral zeroing eliminated artifacts.

Conclusions:

• Transport integral solutions provide accurate predictions for motion-sensitive phase shifts in MR imaging.
• Conventional gradient compensation methods can exacerbate motion artifacts.
• Modifying gradient waveforms by zeroing the second integral effectively eliminates motion artifacts.