Non-Cartesian k-space trajectory calculation based on concurrent reading of the gradient amplifiers' output currents

Area of Science:

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

Background:

• Non-Cartesian imaging sequences require precise knowledge of encoding field gradient dynamics for high-quality image reconstruction.
• Inaccurate field dynamics lead to artifacts and reduced image fidelity in MRI.

Purpose of the Study:

• To develop a measurement-based method for accurately determining magnetic field dynamics during non-Cartesian MRI acquisition.
• To improve k-space trajectory calculation and subsequent image reconstruction quality.

Main Methods:

• Measuring gradient amplifier output currents concurrently with MRI data acquisition.
• Calculating actual dynamic field evolution using a measured current-to-field impulse response function.
• Integrating gradient field evolution to derive accurate k-space trajectories.

Main Results:

• The proposed current-based approach demonstrated slightly improved image quality in spiral and ultrashort TE phantom imaging.
• This improvement was attributed to better modeling of eddy current effects and amplifier nonlinearities.
• The method offers a robust, measurement-based alternative to conventional model-based trajectory calculations.

Conclusions:

• A novel, purely measurement-based method for trajectory calculation in non-Cartesian MRI is presented.
• This approach effectively mitigates gradient amplifier imperfections with minimal hardware requirements.
• The technique provides a robust alternative to model-based methods, enhancing MRI image reconstruction accuracy.