BACKGROUND The purpose of this study was to establish the feasibility of three-dimensional (3D) balanced steady-state-free-precession (bSSFP) myocardial perfusion cardiovascular magnetic resonance (CMR) at 3T using local RF shimming with dual-source RF transmission, and to compare it with spoiled gradient echo (TGRE) acquisition. METHODS Dynamic contrast-enhanced 3D bSSFP perfusion imaging wa...

At high magnetic field strengths (≥ 3T), the radiofrequency wavelength used in MRI is of the same order of magnitude of (or smaller than) the typical sample size, making transmit magnetic field (B1+) inhomogeneities more prominent. Methods such as radiofrequency-shimming and transmit SENSE have been proposed to mitigate these undesirable effects. A prerequisite for such approaches is an accurat...

The general expression for magnetic induction in the z axis direction is derived from magnetic scalar potential, and magnetic induction for biplanar shimming coils (BSCs) is also derived from magnetic vector potentials and Green functions, which simultaneously include Sin and Cos harmonic fields. The relationship between these expressions is discussed, and we show they are partially consistent....

INTRODUCTION The B1 inhomogeneity is well known to be a source of artifact in high field MRI, and requires the use of multiple-channel parallel transmit coil to reduce the artifact by making either the B1 distribution (static shimming) or the flip angle distribution (dynamic shimming) as uniform as possible [1]. The former method complies with most imaging sequences, albeit limited to a small R...

INTRODUCTION: Echo-planar imaging (EPI) and its variants form the core of many functional and structural imaging studies. Image quality of these scans deteriorates drastically with increasing B0 inhomogeneities. Although post-processing can correct aspects related to image distortion, the only way to prevent signal dropout is by improved shimming. Commonly, higher-order static spherical harmoni...

Fig. 2 The three z-shim images evaluated by real time optimization are combined into a MIP image showed in the 4 column. The MIP image consisted of three z-shim images by traditional z-shimming method is showed in the 5 column. Fig. 1 The comparison of real time optimization and traditional z-shimming sweep. Each spot means the intensity summation of z-shim image. The black star symbol indicate...

The homogenization of B0 conditions is necessary for every magnetic resonance spectroscopy (MRS) investigation. Its direct consequence is narrow spectral lines, on which reliable separation and quantification of biochemicals, and thus experimentally obtainable metabolic information, fundamentally relies. Besides spectral linewidth, unwanted B0 inhomogeneity also impairs other aspects of the MRS...

In this work, a shim method that minimizes the maximum off-resonance frequency (min-max shim) in balanced steady-state free precession (bSSFP) is tested for brain imaging at 3T with constant and linear shim terms. The method demonstrates improvement of spatial coverage and banding artifact reduction over standard least-squares shimming. In addition, a new method (modified min-max shim) is intro...