Purpose To develop and evaluate an improved velocity‐selective (VS) labeling pulse for myocardial arterial spin labeling (ASL) perfusion imaging that addresses two limitations of current pulses: (1) spurious labeling of moving myocardium and (2) low labeling efficiency. Methods The proposed myocardial VSASL labeling pulse is designed using a Fourier Transform based Velocity‐Selective labeling pulse train. The pulse utilizes bipolar velocity‐encoding gradients, a 9‐tap velocity‐encoding envelope, and double‐refocusing pulses with Malcolm Levitt phase cycling. Amplitudes of the velocity‐encoding envelope were optimized to minimize the labeling of myocardial velocities during stable diastole (±2‐3 cm/s) and maximize the labeling of coronary velocities (10‐130 cm/s during rest/stress or 10‐70 cm/s during rest). Myocardial ASL experiments were performed in seven healthy subjects using the previously developed VS‐ASL protocol by Jao et al with the two proposed VS pulses and original VS pulse. Myocardial ASL experiments were also performed using FAIR ASL. Myocardial perfusion and physiological noise (PN) were evaluated and compared. Results Bloch simulations of the first and second proposed pulses show <2% labeling over ±3 cm/s and ±2 cm/s, respectively. Bloch simulations also show the mean labeling efficiency of arterial blood is 1.23 over the relevant coronary arterial ranges. In‐vivo VSASL experiments show the proposed pulses provided comparable measurements to FAIR ASL and reduced TSNR in 5 of 7 subjects compared to the original VS pulse. Conclusion We demonstrate an improved VS labeling pulse specifically for myocardial ASL perfusion imaging to reduce spurious labeling of moving myocardium and PN.

Objectives: Multiparametric renal magnetic resonance imaging (MRI), including diffusion-weighted imaging, magnetic resonance elastography, and magnetization transfer imaging (MTI), is valuable in the noninvasive assessment of renal fibrosis. However, hemodynamic changes in diseased kidneys may impede their ability to measure renal fibrosis. Because MTI assesses directly tissue content of macromolecules, we test the hypothesis that MTI would be insensitive to renal hemodynamic changes in swine kidneys with acute graded ischemia. Materials and Methods: Seven domestic pigs underwent placement of an inflatable silicone cuff around the right renal artery to induce graded renal ischemia. Multiparametric MRI was performed at baseline, 50%, 75%, and 100% renal artery stenosis as well as reperfusion. Measurements included regional perfusion, R 2 *, apparent diffusion coefficient (ADC), stiffness, and magnetization transfer ratio (MTR) using arterial spin-labeled MRI, blood oxygenation-dependent MRI, diffusion-weighted imaging, magnetic resonance elastography, and MTI, respectively. Histology was performed to rule out renal fibrosis. Results: During graded ischemia, decreases in renal perfusion were accompanied with elevated R 2 *, decreased ADC, and stiffness, whereas no statistically significant changes were observed in the MTR. No fibrosis was detected by histology. After release of the obstruction, renal perfusion showed only partial recovery, associated with return of kidney R 2 *, ADC, and stiffness to baseline levels, whereas cortical MTR decreased slightly. Conclusions: Renal MTI is insensitive to decreases in renal perfusion and may offer reliable assessment of renal structural changes.

The GRATER sequence measures small-tip RF envelopes without extra hardware or synchronization in just over two times the RF duration. The sequence may be useful in prescan calibration and for measurement and precompensation of RF amplifier nonlinearity. Magn Reson Med 79:2642-2651, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Purpose: To develop a cardiac T 1 mapping method for free-breathing 3D T 1 mapping of the whole heart at 3 T with transmit B 1 (B + 1 ) correction. Methods: A free-breathing, electrocardiogram-gated inversion-recovery sequence with spoiled gradient-echo readout was developed and optimized for cardiac T 1 mapping at 3 T. High-frame-rate dynamic images were reconstructed from sparse (k,t)-space data acquired along a stack-of-stars trajectory using a subspace-based method for accelerated imaging. Joint T 1 and flip-angle estimation was performed in T 1 mapping to improve its robustness to B + 1 inhomogeneity. Subject-specific timing of data acquisition was used in the estimation to account for natural heart-rate variations during the imaging experiment.Results: Simulations showed that accuracy and precision of T 1 mapping can be improved with joint T 1 and flip-angle estimation and optimized electrocardiogramgated spoiled gradient echo-based inversion-recovery acquisition scheme. The phantom study showed good agreement between the T 1 maps from the proposed method and the reference method. Three-dimensional cardiac T 1 maps (40 slices) were obtained at a 1.9-mm in-plane and 4.5-mm through-plane spatial resolution from healthy subjects (n = 6) with an average imaging time of 14.2 ± 1.6 minutes (heartbeat rate: 64.2 ± 7.1 bpm), showing myocardial T 1 values comparable to those obtained from modified Look-Locker inversion recovery. The proposed method generated B + 1 maps with spatially smooth variation showing 21%-32% and 11%-15% variations across the septal-lateral and inferior-anterior regions of the myocardium in the left ventricle. Conclusion:The proposed method allows free-breathing 3D T 1 mapping of the whole heart with transmit B 1 correction in a practical imaging time.