Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine
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This article focuses on developing a novel noniterative fat water decomposition algorithm more robust to fat water swaps and related ambiguities. ⋯ The proposed algorithm is capable of considerably reducing the swaps in challenging fat water decomposition problems. The experiments demonstrate the benefit of using explicit smoothness constraints in field map estimation and solving the problem using a globally convergent graph-cut optimization algorithm.
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To enable highly accelerated RARE/Turbo Spin Echo (TSE) imaging using Simultaneous MultiSlice (SMS) Wave-CAIPI acquisition with reduced g-factor penalty. ⋯ Combination of the two technologies, Wave-CAIPI and MultiPINS pulse, enables highly accelerated RARE/TSE imaging with low SNR penalty at reduced SAR.
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Neurovascular regulation, including responses to neural activation that give rise to the blood oxygenation level-dependent (BOLD) effect, occurs mainly at the arterial and arteriolar level. The purpose of this study is to develop a framework for fast imaging of arterial cerebral blood volume (aCBV) signal suitable for functional imaging studies. ⋯ AVAST exhibits improved activation detection sensitivity and temporal resolution over the standard ASL technique, in functional MRI experiments, while preserving its quantitative nature and statistical advantages. AVAST particularly could be useful in clinical studies of pathological conditions, longitudinal studies of cognitive function, and studies requiring sustained periods of the condition.
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Echo planar-based diffusion-weighted MRI (DW-MRI) requires robust suppression of fat signal. Fat suppression techniques such as inversion recovery or spectrally selective excitation with subsequent gradient spoiling can extend scan time or perform suboptimally in the presence of strong main field inhomogeneities. Chemical shift-encoded water-fat separation using iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) is robust in areas of main field inhomogeneity but requires accurate phase information, which can be distorted by patient motion during diffusion-weighting gradients. A method is proposed to overcome this with the use of image navigators. ⋯ DW-EPI with IDEAL and an integrated image navigator allows for robust water and fat separation in different body areas and are a time-efficient alternative to standard fat-suppression techniques in DW-MRI.
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MR thermometry (MRT) is a noninvasive method for measuring temperature that can potentially be used for radio frequency (RF) safety monitoring. This application requires measuring absolute temperature. In this study, a multigradient-echo (mGE) MRT sequence was used for that purpose. A drawback of this sequence, however, is that its accuracy is affected by background gradients. In this article, we present a method to minimize this effect and to improve absolute temperature measurements using MRI. ⋯ The corrections offer the possibility to measure RF heating in phantoms more precisely. This allows mGE MRT to become a valuable tool in RF safety assessment.