Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine
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Comparative Study
Quantitative cerebral blood flow with bolus tracking perfusion MRI: measurements in porcine model and comparison with H(2)(15)O PET.
We recently presented a method for the quantitative measurement of the arterial input function which allows for determination of absolute cerebral blood flow (CBF) values without adjustable parameters. The aim of the present work is to estimate absolute CBF values by using this new technique and to compare it with the gold standard for cerebral perfusion, H(2)(15)O positron emission tomography. ⋯ The proposed method allows for determination of quantitative CBF without normalization factors. The relatively low estimates of absolute CBF most likely results from the higher age of the pigs as compared to other studies. The intermediate correlation between both methods is caused by physiological intraindividual fluctuations of the CBF and by a limited reproducibility of both methods.
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Ultrafast sequences based on "Hybrid" spatiotemporal encoding (SPEN) replace echo-planar imaging's phase encoding "blips," while retaining a k-space readout acquisition. Hardware imperfections during acquisition may lead to ghosts and striped artifacts along the SPEN dimension; akin to echo-planar imaging's Nyquist ghosts, but weaker. A referenceless method to eliminate these artifacts in Hybrid SPEN is demonstrated. ⋯ The referenceless correction enables robust single-scan imaging under changing conditions-such as patient motion and changes in shimming over time-without the need of ancillary navigators. This opens new options for real-time MRI and interactive scanning.
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MR histology based on magnetic susceptibility can be used to visualize diamagnetic myelin (and its deterioration) in the central nervous system and is facilitated by the application of high magnetic field strengths and paramagnetic contrast agents. Characterizing the effect of these tools will aid in assessing white matter myelin content and microstructure. ⋯ Using contrast agents in MR histology facilitates white-gray matter susceptibility contrast modulation and the probing of white matter microstructure and orientation.
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Randomized Controlled Trial
Whole-brain three-dimensional T2-weighted BOLD functional magnetic resonance imaging at 7 Tesla.
A new acquisition scheme for T2-weighted spin-echo BOLD fMRI is introduced. ⋯ This approach is expected to be useful for ultra-high field fMRI, especially for regions near air cavities. The concept of using T2-preparation to generate BOLD contrast can be combined with many other sequences at any field strength.
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In this study, we aim to demonstrate the sensitivity of proton resonance frequency shift (PRFS) -based thermometry to heat-induced magnetic susceptibility changes and to present and evaluate a model-based correction procedure. ⋯ This study has shown the effects of magnetic susceptibility changes induced by heating of breast fatty tissue samples. The resultant errors can be reduced by the use of a model-based correction procedure.