Adaptive Shim Coils for MRI Field Uniformity

The patent applies local quality by creating different magnetic field characteristics in different spatial regions. The shim gradient coil generates a perturbed magnetic field that is intentionally non-uniform, with high uniformity specifically within the user-defined region of interest and deliberately degraded uniformity outside this region. This allows the system to optimize field quality locally where needed rather than uniformly across the entire field-of-view, thereby reducing imaging time without sacrificing image quality in the region of interest.

The patent employs parameter changes by dynamically adjusting the magnetic field parameters through the shim gradient coil. Specifically, it modifies the magnetic field distribution parameters to create a perturbed state where the field uniformity parameter is optimized for the region of interest while accepting degraded uniformity elsewhere. This parameter adjustment allows reduced field-of-view imaging without the usual penalty of increased field inhomogeneity and associated artifacts.

The patent converts the harmful effect of field inhomogeneity outside the region of interest into a beneficial feature. By intentionally using the shim gradient coil to create degraded field uniformity outside the ROI, the system achieves faster imaging times and improved efficiency for the region of interest. The normally undesirable field perturbations are deliberately employed as a mechanism to suppress signals from areas outside the ROI, transforming what would be artifacts into a useful signal suppression technique that improves overall imaging productivity.