Phantom-based gradient waveform measurements with compensated variable-prephasing: Description and application to EPI...

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Gradient Coil Engineering
• Signal Processing in MRI

Background:

• Accurate gradient waveform measurement is crucial for advanced MRI techniques.
• Existing methods like variable-prephasing (VP) have limitations due to uncompensated gradient effects.
• Precise gradient characterization is essential for trajectory corrections in fast imaging sequences.

Purpose of the Study:

• Introduce compensated variable-prephasing (CVP), an enhanced phantom-based method for gradient waveform measurement.
• To evaluate the performance of CVP against traditional VP and fully compensated variable-prephasing (FCVP).
• To assess the utility of measured gradient waveforms for trajectory corrections in echo-planar imaging (EPI).

Main Methods:

• Measurements of trapezoidal and EPI readout gradients using VP, CVP, and FCVP techniques.
• Comparison of measured waveforms with predictions derived from the gradient system transfer function.
• Application of measured and predicted EPI gradients for trajectory corrections in phantom imaging at 7T.

Main Results:

• VP measurements were affected by prephasing gradient oscillations, which CVP and FCVP successfully compensated.
• FCVP demonstrated vulnerability to sign asymmetry within the gradient system.
• Despite method variations, all three approaches yielded comparable high-quality EPI images.

Conclusions:

• Compensated variable-prephasing (CVP) provides a highly precise method for phantom-based gradient waveform measurements.
• This technique is valuable for trajectory corrections in non-Cartesian and single-shot MRI sequences.
• CVP emerged as the most reliable method for gradient measurements in the comparative experimental setup.