Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine
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To determine the optimal flip angle (FA) for cardiac cine imaging that maximizes myocardial signal and blood-myocardium contrast. ⋯ Very high blood-myocardium CNR can be obtained with a FA of ≈105° in the short-axis plane and ≈75° in the three-chamber and four-chamber imaging planes. However, if through-plane flow is limited, as may occur for patients with low ejection fraction or low heart rates, then the FA may be limited to ≈ 75°.
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To analyze the flip angle dependence and to optimize the statistical precision of a fast three-dimensional (3D) T1 mapping technique based on the variable flip angle (VFA) method. The proposed single flip angle (1FA) approach acquires only a single 3D spoiled gradient echo data set for each time point of the dynamical series in combination with a longer baseline measurement. ⋯ The proposed flip angle-optimized 1FA technique optimizes the precision of T1 values in dynamic phantom measurements.
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A feasibility study of an echo-planar spectroscopic imaging (EPSI) using a short echo time (TE) that trades off sensitivity, compared with other short-TE methods, to achieve whole brain coverage using inversion recovery and spatial oversampling to control lipid bleeding. ⋯ The present EPSI method enables estimation of the whole-brain metabolite distributions, including Glx and mI with small voxel size, and a reasonable scan time and reproducibility.
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Comparative Study
Comparison of simulated parallel transmit body arrays at 3 T using excitation uniformity, global SAR, local SAR, and power efficiency metrics.
We compare the performance of eight parallel transmit (pTx) body arrays with up to 32 channels and a standard birdcage design. Excitation uniformity, local specific absorption rate (SAR), global SAR, and power metrics are analyzed in the torso at 3 T for radiofrequency (RF)-shimming and 2-spoke excitations. ⋯ PTx coils can simultaneously improve the excitation uniformity and reduce SAR compared to a birdcage coil when SAR metrics are explicitly constrained in the pulse design.
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Velocity-selective arterial spin labeling (VSASL) tags arterial blood on a velocity-selective (VS) basis and eliminates the tagging/imaging gap and associated transit delay sensitivity observed in other ASL tagging methods. However, the flow-weighting gradient pulses in VS tag preparation can generate eddy currents (ECs), which may erroneously tag the static tissue and create artificial perfusion signal, compromising the accuracy of perfusion quantification. ⋯ The sym-BIR-8 design performed the most robustly among the existing VS tagging designs, and should benefit studies using VS preparation with improved accuracy and reliability.