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Carotid atherosclerosis measurements for eight subjects at baseline and 14 +/- 2 days later were examined using 1.5 T and 3.0 T magnetic resonance imaging (MRI). A single observer blinded to field strength, subject and timepoint manually segmented carotid artery wall and lumen boundaries in randomized images in five measurement trials. Mean increases in the(More)
PURPOSE To develop a new method of reducing T1 bias in proton density fat fraction (PDFF) measured with iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL). MATERIALS AND METHODS PDFF maps reconstructed from high flip angle IDEAL measurements were simulated and acquired from phantoms and volunteer L4(More)
PURPOSE A new approach to mapping the flip angle quickly and efficiently in 3D based on the Look-Locker technique is presented. METHODS We modified the accelerated 3D Look-Locker T1 measurement technique to allow rapid measurement of flip angle. By removing the inversion pulses and interleaving two radio frequency pulses with different amplitude, it is(More)
PURPOSE To develop and evaluate a rapid spherical navigator echo (SNAV) motion correction technique, then apply it for retrospective correction of brain images. METHODS The pre-rotated, template matching SNAV method (preRot-SNAV) was developed in combination with a novel hybrid baseline strategy, which includes acquired and interpolated templates.(More)
PURPOSE To accurately analyze vibroacoustics in MR head gradient coils. THEORY AND METHODS A detailed theoretical model for gradient coil vibroacoustics, including the first description and modeling of Lorentz damping, is introduced and implemented in a multiphysics software package. Numerical finite-element method simulations were used to establish a(More)
PURPOSE To implement and optimize a single-shot spiral encoding strategy for rapid 2D IDEAL projection imaging of hyperpolarized (Hp) (129) Xe in the gas phase, and in the pulmonary tissue (PT) and red blood cells (RBCs) compartments of the rat lung, respectively. THEORY AND METHODS A theoretical and experimental point spread function analysis was used to(More)
Ultra High Field (UHF) MRI requires improved gradient and shim performance to fully realize the promised gains (SNR as well as spatial, spectral, diffusion resolution) that higher main magnetic fields offer. Both the more challenging UHF environment by itself, as well as the higher currents used in high performance coils, require a deeper understanding(More)
PURPOSE To demonstrate a reconstruction technique for separating signal from different hyperpolarized carbon-13 metabolites. METHODS A reconstruction method is described for chemical shift encoded separation of the signal from pyruvate and its downstream metabolites. This method uses consistency of the data with the signal model rather than an additional(More)
PURPOSE To demonstrate a new multigradient echo bipolar acquisition sequence for fat quantification. THEORY AND METHODS A multiecho bipolar acquisition is used such that the even echoes have opposite polarity to the odd echoes. In addition, the readout gradients alternate their polarities every other phase-encode line. Each echo, therefore, consists of(More)
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