Topics in magnetic resonance imaging : TMRI
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Top Magn Reson Imaging · Jun 2010
ReviewCurrent problems and future opportunities of abdominal magnetic resonance imaging at higher field strengths.
Introduction of high-field-strength whole-body MR scanners to clinical routine made abdominal magnetic resonance (MR) imaging widely available. Higher field strength provides improved signal yield, but other issues such as shorter wavelength and increased power deposition of radiofrequency in tissue must also be taken into account. ⋯ General safety issues and limitations in radiofrequency power deposition are discussed. Subsequently, implications of the previously mentioned changed MR properties at 3.0 T on clinical abdominal examinations applying different sequence types are described.
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Top Magn Reson Imaging · Oct 2009
ReviewFunctional MRI evidence for distinctive binding and consolidation pathways for face-name associations: analysis of activation maps and BOLD response amplitudes.
Although some of the anatomical underpinnings of learning and memory systems have been identified, there remains little understanding of how the brain moves from acquiring new information to retaining it. This study was designed to further explore and elucidate the neural mechanisms underlying encoding and memory in a common real-life task, that is, face-name associations. One possible outcome is that the tasks will recruit different neural structures mediating these processes, which can be identified through contrast analysis of activations. Alternatively, it is possible that similar anatomical regions, such as the hippocampus and parahippocampal gyrus, may be involved in both tasks. In that case, analysis of blood oxygenation level dependent (BOLD) amplitude differences between the tasks in those common neural structures may be able to detect whether physiological activation differences occur in encoding versus memory. ⋯ Higher BOLD response amplitudes in the right fusiform gyrus and the right hippocampus during face-name encoding suggest a potentially specific binding pathway where disparate information might be neurally linked. In contrast, the increased BOLD response in the lingual gyrus during recognition memory may indicate a key neural substrate for memory consolidation and long-term knowledge of what is learned. Whole-brain activation maps revealed task-specific differences in areas of the prefrontal, temporal, and occipital-parietal-temporal junctions as well. Findings suggest that there are distinctive anatomical and physiological nodes for face-name learning and memory within large-scale cortical-subcortical networks. Hence, lesions in fairly widespread cerebral regions may potentially disrupt specific binding and/or memory consolidation processes.
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Top Magn Reson Imaging · Jun 2009
Review3T magnetic resonance imaging of ankle and hindfoot tendon pathology.
Ankle tendon pathology is relatively common in the active adult population. Magnetic resonance imaging is often the preferred advanced imaging option for the evaluation of tendon pathology of the hindfoot and ankle. The almost linear increase in signal-to-noise ratio provided by higher field strength imaging allows for improved image resolution and decreased scan times. ⋯ The ability to comfortably scan the ankle within the magnet isocenter using high-field strength-compatible extremity coils further maximizes the image resolution. It is imperative for the radiologist to be aware of necessary protocol adjustments and potential imaging artifacts unique to high-field strength imaging of the ankle. Our review outlines high-field strength magnetic resonance imaging technique and artifacts and also details the specifics of our own methods of ankle imaging.
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Top Magn Reson Imaging · Jan 2009
Clinical TrialAwake craniotomy and intraoperative magnetic resonance imaging: patient selection, preparation, and technique.
Intraoperative magnetic resonance imaging (iMRI) has been reported to augment radical brain tumor resection. "Awake craniotomy" is a technique to conserve function during brain tumor surgery. We report on the combination of these 2 techniques, with special emphasis on potential adverse effects, caveats, and patient preparation. ⋯ The combination of iMRI and awake craniotomy is demanding but well tolerated by patients. Careful preoperative evaluation is essential to ensure compliance. There is no adverse effect through iMRI on the awake patient or the results of cortical stimulation. Since the introduction of the iMRI in our department in 2005, all awake craniotomies were done in this setting. The implementation of these 2 techniques into our procedures is demanding, and necessitates thorough preparation but has broadened our basis for surgical decision making. However, to substantiate our positive perception, more clinical data are being compiled.
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Top Magn Reson Imaging · Jan 2009
Clinical TrialFunctional magnetic resonance imaging-guided brain tumor resection.
We evaluated the safety and efficacy of using functional magnetic resonance imaging (fMRI) brain activation data obtained at both 1.5 and 3 T to guide brain tumor resections using 1.5-T intraoperative MRI (ioMRI) guidance. ⋯ Functional MRI was accurate for localizing areas of eloquent neurologic function before ioMRI-guided brain tumor resection.