Introduction At high field strengths, shimming becomes increasingly more difficult and important since susceptibility induced B0 inhomogeneities increase. Exploiting up to 3 rd order shim coils on the system, a high number of degrees of freedom are available to generate a more homogeneous B0 field. In MR spectroscopy excellent shimming is an important factor for acquiring high quality data sinc...

A subject-specific local in vivo passive shimming method, focusing on the prefrontal and temporal regions, is proposed. The aim of the investigation is to show that subject variability exists in optimal passive shimming and that the proposed method can be effectively used to overcome these differences. A shimming structure capable of adjusting the position of the passive shims to within a milli...

MR susceptometry-based blood oximetry relies on phase mapping to measure the difference in magnetic susceptibility between intravascular blood and surrounding tissue. The main source of error in MR susceptometry is the static field inhomogeneity caused by an interface between air and tissue or between adjacent tissue types. High-pass filtering has previously been used in conjunction with shimmi...

We propose a new passive shimming strategy for variable-field NMR experiments, in which the magnetic field produced by paramagnetic shim pieces placed inside the magnet bore compensates the inhomogeneity of a variable-field magnet for a wide range of magnet currents. Paramagnetic shimming is demonstrated in (7)Li, (87)Rb, and (45)Sc NMR of a liquid solution sample in magnetic fields of 3.4, 4.0...

Introduction RF shimming is a well-known technique, where amplitudes and phases of a transmit RF coil array are optimized to obtain a homogeneous B1 profile, i.e., to compensate wave propagation effects at main fields of 3T or above (see, e.g., [1]). Among other anatomies, legs are particularly prone to wave propagation effects due to their bi-cylindrical geometry, resulting in significant sign...

Purpose Achieving a desired RF transmit field () in small regions of interest is critical for single-voxel MRS at ultrahigh field. Radio-frequency (RF) shimming, using parallel transmission, requires mapping and optimization, which limits its ease use. This work aimed to generate calibration-free shims predefined target interest, can be applied any participant, produce absolute magnitude (||). ...

BACKGROUND In high field MRI capable of multi-channel radio frequency (RF) transmission, B 1 shimming is a time-consuming job because conventional B 1 shimming techniques require B 1 mapping for each channel. After acquiring the complex-numbered B 1 field maps, the optimal amplitude and phase of the driving RF pulse are determined for each channel to maximize the B 1 field uniformity in convent...

Adjustment of the static magnetic field homogeneity, commonly known as the B0 shimming or simply shimming, is essential for magnetic resonance spectroscopy because it determines the spectral resolution which is critical for reliable metabolite quantification. Inhomogeneities in the B0 field, resulting primarily from susceptibility differences between air and tissue, are scaled with the B0 field...

Introduction: With the advent of ultrahigh field systems (7T), significant improvements in spectroscopic imaging (SI) studies of the human brain have been anticipated. However, these gains are dependent upon the achievable B0 homogeneity, both globally (over the entire ROI or slice) and locally (the linewidths of individual SI voxels within the ROI). The goals of this work were to: 1) determine...