Journal of magnetic resonance imaging : JMRI
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J Magn Reson Imaging · Dec 2007
MR imaging of the female pelvis at 3 Tesla: evaluation of image homogeneity using different dielectric pads.
To evaluate improvements in image homogeneity in pelvic MR imaging at 3 Tesla (T) using two different dielectric pads. ⋯ Dielectric pads consisting of either US gel or water are effective in improving image homogeneity of the pelvis on 3T MRI.
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J Magn Reson Imaging · Dec 2007
Detecting groups of coherent voxels in functional MRI data using spectral analysis and replicator dynamics.
To investigate the relationship between functional MRI (fMRI) time series in the human brain, combining fMRI spectral analysis and replicator dynamics. ⋯ The application of replicator dynamics to spectral matrices is a reliable method for detecting groups of maximally coherent voxels. A replicator process is able to determine groups of voxels with the property that each voxel in the group exhibits a high coherence with every other group member. In contrast to the NCV approach, this method is parameter-free and does not require the a priori selection of a reference voxel.
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To develop a voxel-based analysis of an R2* map of healthy human brain that is automatic, reproducible, and realizable in a single examination on a 3T MR imager. Such a tool could be useful to measure iron accumulation in neurodegenerative diseases. ⋯ Our method, combining data acquisition and data processing, demonstrates the feasibility of voxel-based analysis on an R2* map and affords a high degree of sensitivity and good reproducibility while maintaining high spatial resolution.
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J Magn Reson Imaging · Dec 2007
Comparative StudyDirect comparison of myocardial perfusion cardiovascular magnetic resonance sequences with parallel acquisition.
To directly compare the three main myocardial perfusion cardiovascular magnetic resonance (CMR) sequences incorporating parallel acquisition methods. ⋯ The hEPI sequence scored best for diagnostic performance despite the SSFP sequence having greater CNR. This trial favors hEPI for clinical myocardial perfusion CMR and suggests CNR should not be the sole criterion used to gauge the best candidate sequence.
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J Magn Reson Imaging · Dec 2007
Alteration of blood oxygenation level-dependent signaling by local circulatory condition.
To determine regional differences in the relationship between neuronal activation and blood oxygenation level-dependent (BOLD) signal changes. ⋯ Insufficient perfusion pressure in these regions may have led to attenuation of BOLD and perfusion responses to stimulation of a large portion of the visual field, or a condition in which a large extent of the visual areas was activated in the proximal regions of the territories perfused by the middle and posterior cerebral arteries. This finding supports the hypothesis that regional differences in circulatory condition can result in alterations of the relationship between neuronal activation and BOLD signal changes in the normal human brain.