Shimming systems are required to provide sufficient field homogeneity for high resolution nuclear magnetic resonance (NMR). In certain specialized applications, such as rotating-field NMR and mobile ex situ NMR, permanent magnet-based shimming systems can provide considerable advantages. We present a simple two-dimensional shimming method based on harmonic corrector rings which can provide arbi...

Wave propagation effects diminish the quality of MR images at main fields of 3T or above. Parallel RF transmission has the potential of compensating for these effects through RF shimming. RF shimming can be performed in two different ways. The basic way of RF shimming is to adjust the global amplitude and phase of the currents in each transmit element, aiming at a constant B1 in the region of i...

PURPOSE To develop a new shimming calculation method, which can calculate iron piece placements rapidly to make the magnetic field homogeneous at intended homogeneity and then to make the shimming working time short. MATERIALS AND METHODS The shimming calculation yields magnetic moment (MM) distribution, which is calculated by the truncated singular value decomposition (SVD) from the measured...

PURPOSE Intramyocardial hemorrhage and area at risk are both prognostic markers in acute myocardial infarction (AMI). Myocardial T2 and T2 * mapping have been used to detect such tissue changes at 1.5T but these techniques are challenging at 3.0T due to additional susceptibility variation. We studied T2 and T2 * myocardial mapping techniques at 3.0T on a system employing B1 shimming and compare...

Inadequate B0-shimming regularly results in suboptimal clinical image quality for several imaging and spectroscopic techniques. Linear shimming is generally a standard commercial offering, and higher-order shimming hardware is also available; however, these tools can be highly operator-dependent. While sporadic recommendations are in the literature, in practice, shimming strategies are typicall...

shimming > epi; right: epi > z-shimming. P < 0.05 uncorrected. Fig. 2. Activation map from 6 subjects using z-shimming (left) and normal EPI (right). P < 0.01 uncorrected. Fig. 1. schematic drawing of the volume selective z-shimming slices. Solid lines: actual slices for imaging; solid red lines: slices to apply z-shim; dashed red lines: virtual slices during slice positioning, the actual slice...

BACKGROUND Radiofrequency (RF) shading artifacts degrade image quality while performing cardiovascular magnetic resonance (CMR) at higher field strengths. In this article, we sought to evaluate the effect of local RF (B1 field) shimming by using a dual-source-transmit RF system for cardiac cine imaging and to systematically evaluate the effect of subject body type on the B1 field with and witho...

Cardiac MRI may benefit from increased polarization at high magnetic field strength of 3 Tesla but is challenged by increased field inhomogeneity. Initial human studies have shown that the radiofrequency (RF) excitation field (B1+) used for signal excitation in the heart is both inhomogeneous and significantly lower than desired, potentially leading to image artifacts and biased quantitative me...

The shimming method used for producing high field homogeneity of the open permanent main magnet for magnetic resonance imaging (MRI) is researched in this paper. The central shimming method based on integer programming is proposed, which fulfills the combination of optimal theory and the practical manual shimming. The formulation of shimming is solved by using Lingo software and the numerical a...