Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine
-
To perform multi-echo water/fat separated proton resonance frequency (PRF)-shift temperature mapping. ⋯ The proposed model-based water/fat separated algorithm produces accurate PRF-shift temperature maps in mixed water and fat tissues in the presence of spatiotemporally varying off-resonance and motion.
-
To develop a dynamic contrast-enhanced (DCE) MRI method capable of high spatiotemporal resolution, 3D carotid coverage, and T1-based quantification of contrast agent concentration for the assessment of carotid atherosclerosis using a newly developed Multitasking technique. ⋯ Multitasking DCE is a promising approach for quantitatively assessing the vascularity properties of the carotid vessel wall.
-
Managing local specific absorption rate (SAR) in parallel transmission requires ensuring that the peak SAR over a large number of voxels (> 10 5 ) is below the regulatory limit. The safety risk to the patient depends on cumulative (not instantaneous) SAR thus making a joint design of all RF pulses in a sequence desirable. We propose the Iterative Minimization Procedure with Uncompressed Local SAR Estimate (IMPULSE), an efficient optimization formulation and algorithm that can handle uncompressed SAR matrices and optimize pulses for all slices jointly within a practical time frame. ⋯ IMPULSE can handle significantly larger number of SAR matrices and slices than conventional optimization algorithms, enabling the use of uncompressed or partially compressed SAR matrices to design pulses for a multislice scan in a practical time frame.
-
For clinical implementation, a chemical exchange saturation transfer (CEST) imaging sequence must be fast, with high signal-to-noise ratio (SNR), 3D coverage, and produce robust contrast. However, spectrally selective CEST contrast requires dense sampling of the Z-spectrum, which increases scan duration. This article proposes a compromise: using a 3D snapshot gradient echo (GRE) readout with optimized CEST presaturation, sampling, and postprocessing, highly resolved Z-spectroscopy at 3T is made possible with 3D coverage at almost no extra time cost. ⋯ A sophisticated CEST tool ready for clinical application was developed and tested for feasibility.
-
To assess the influence of background suppression and retrospective realignment on physiological noise and image quality in free-breathing renal pseudo-continuous arterial spin labeling (pCASL). ⋯ Renal perfusion measurement with ASL under free breathing is feasible and robust against physiological noise when using strong background suppression strategies. Finally, retrospective motion-correction further improves image quality but cannot replace background suppression.