Speaker
Description
In the design of ultrahigh field magnetic resonance imaging (MRI) superconducting magnets, it typically requires a high homogeneous magnetic field in the diameter of spherical volume (DSV) to obtain high quality image. Spherical harmonic based B0 shimming relies significantly on the fitting process, which can be computationally demanding, especially when handling a large number of shim coils. This study introduces an active shimming method that optimizes magnetic field homogeneity by acquiring the FID signal at each layer. It uses the full width at half maximum (FWHM) of the spectrum for each layer as a metric and iteratively adjusts the shim coil current. By minimizing the FWHM, this approach efficiently identifies the optimal shimming coil current, significantly enhancing spatial field homogeneity. The experimental validation conducted on a 7 T MRI superconducting magnet confirmed the efficacy of the suggested approach. Specifically, employing gradient coils and active shim coils, the active shimming approach increased the field homogeneity of a 130 mm DSV, resulting in a much better magnetic field environment for subsequent MRI. Furthermore, this method enables rapid shimming before imaging, substantially reducing the time required for imaging preparation.
