Enhanced Slab Selective Brain Imaging at 3T using Wide Band Tailored RF pulses
نویسندگان
چکیده
Introduction T1 weighted brain imaging at 3T for both clinical and neuroscience applications is often done using slab selective MPRAGE [1] sequences that provide flexible 3D coverage. RF field (B1) non-uniformity is an inherent problem for high field MRI and for this type of sequence results in variable image contrast. In order to compensate for this, various B1 inhomogeneity mitigating RF pulses have been proposed, and for slice or slab selective imaging the most popular are the so-called "spokes" or “fast kz” [2,3] pulses. These consist of a train of slice/slab selective pulses (“spokes”) which are individually modulated to produce the desired excitation. Parallel transmission (PTx) can be incorporated into this framework, by applying different pulses on each RF coil. We designed and tested an enhanced PTx-spokes implementation of a clinically used slab selective MPRAGE protocol for at 3T.and have explored the relative merits of simple RF shimming, single channel spokes operation and full PTx with spokes.
منابع مشابه
Time-Efficient Slab Selective Water Excitation
Introduction Spectral spatial (SPSP) RF pulses are simultaneously selective in both the spectral and spatial domains [1]. SPSP pulses consist of a train of slice selective RF subpulses applied simultaneously with an oscillating slice select gradient. When used for spatially selective water or fat excitation, the difference in frequency between water and fat, ∆ , limits the spacing between RF su...
متن کاملZ-stacked RF array design enhances parallel transmit multiband RF performance in whole brain simultaneous multislice imaging at 7T
Introduction: Simultaneous MultiSlice (SMS) MR imaging (1) using MultiBand (MB) RF pulses is becoming increasingly popular in the neuroimaging community (2-4). Recently, there has been an interest in utilizing multielement RF arrays in combination with multichannel (pTx) MB pulse design to reduce transmit B1 (B1+) inhomogeneity and SAR (5,6) for SMS/MB imaging. Meanwhile, it has been shown that...
متن کاملBasic and Tailored RF Shimming in a Multi-transmit Whole Body MR System
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...
متن کاملSlice profile optimization in arterial spin labeling using presaturation and optimized RF pulses.
OBJECTIVE An important source of error in arterial spin labeling (ASL) is incomplete static tissue subtraction due to imperfect slice profiles. This effect can be reduced by saturating the spins in the imaging area prior to labeling. In this study, the use of optimized presaturation is compared with the use of optimized RF pulses for minimizing this error. MATERIALS AND METHODS Different meth...
متن کاملSingle-shot line scan imaging using stimulated echoes.
A new high-speed MRI method is described for single-shot line scan imaging (LSI) based on stimulated echoes (STE). To allow for multislice imaging, the technique comprises a series of slice-selective preparation pulses (each corresponding to the first RF pulse of a STE sequence), a slab-selective refocusing pulse (second RF pulse), and multiple line-selective read pulses (third RF pulses). An a...
متن کامل