Topics in magnetic resonance imaging : TMRI
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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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Cerebral perfusion imaging using magnetic resonance imaging (MRI) is widely used in the research and clinical fields to assess the profound changes in blood flow related to ischemic events such as acute stroke, chronic steno-occlusive disease, vasospasm, and abnormal vessel formations from congenital conditions or tumoral neovascularity. With continuing improvements in the precision of MRI-based perfusion techniques, it is increasingly feasible to use this tool in the study of the subtle brain perfusion changes occurring in psychiatric illnesses. This article aims to review the existing literature on applications of perfusion MRI in psychiatric disorder and substance abuse research. The article also provides a brief introductory overview of dynamic susceptibility contrast MRI and arterial spin labeling techniques. An outlook of necessary steps to bring perfusion MRI into the realm of clinical psychiatry as a diagnostic tool is brought forth. Opportunities for research in unexplored disorders and with higher field strengths are briefly examined. ⋯ Although MRI-based perfusion imaging in psychiatry has mainly been used as a research tool, a path is progressively being cleared for its application in clinical diagnostic and treatment monitoring. The precision of perfusion MRI methods now rivals that of nuclear medicine-based perfusion imaging techniques. Because of their noninvasive nature, arterial spin labeling methods have gained popularity in studies of neuropsychiatric disorders such as schizophrenia, depression, Alzheimer's, and Parkinson's diseases. Perfusion imaging measurements have yet to be included within the diagnostic criteria of neuropsychiatric disorders despite having shown to have great discriminant power in specific disorders. As this young methodology continues to improve and research studies demonstrate the correlation of measured perfusion abnormalities to microcirculatory abnormalities and neuropsychiatric symptomatology, the idea of including such a test within diagnostic criteria for certain mental illnesses becomes increasingly plausible.
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Top Magn Reson Imaging · Feb 2008
ReviewRole of cardiac magnetic resonance imaging in assessment of nonischemic cardiomyopathies.
Diagnosis of nonischemic cardiomyopathy is a challenging process that influences patient morbidity and mortality. Currently, the well known World Health Organization classification has been revisited by an American Heart Association expert consensus panel. ⋯ Magnetic resonance imaging is a robust diagnostic tool that offers various techniques to assess the function, morphology, perfusion, and scarring of myocardial tissue thus providing better understanding of the underlying causes of nonischemic cardiomyopathies. In this review, we discuss the current role of cardiac MRI in the evaluation of nonischemic cardiomyopathy, in the context of the current American Heart Association classification of these disorders.
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The oral cavity is anterioly located and unique in the variety of tissues contained in this area. Although oral cancer screening may be done on clinical examination, imaging plays a critical role in staging and determination of deep margins for either tumor resectability or radiation planning. ⋯ This is followed by a discussion of standard MRI techniques, American Joint Committee on Cancer (AJCC) classification, and relevant MRI findings with discussion and imaging examples of carcinoma in major sites, including floor of mouth, oral tongue, buccal mucosa, bony upper alveolus, hard palate, and retromolar trigone. A brief summary of newer imaging techniques for evaluation of oral cancer is also presented.