Open-Source Algorithm for 3D Gradient Nonlinearity Characterization Using a Rigid Arrangement of NMR Field Probes

Motivation: MRI users rely on vendor-specific means to correct for distortions due to gradient nonlinearity. This study endeavors to measure gradient nonlinearities without a dedicated phantom for MR systems where accurate correction parameters are unavailable. Goal(s): Develop a nonproprietary gradient nonlinearity measurement procedure. Approach: We conduct NMR field probe measurements to determine the gradient nonlinearity. A dedicated algorithm detects inconsistencies between the apparent probe positions and seeks the optimal spherical harmonic coefficients correcting for distortions. Results: We demonstrate the feasibility of the proposed measurement and a reduction of distortions in MR images. Impact: The proposed nonproprietary approach for measuring gradient nonlinearity induced distortions without a dedicated phantom has the potential to promote accuracy and reproducibility of imaging studies across different MRI systems, if the sites are equipped with a field camera.