Neuroimaging clinics of North America
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Diffuse axonal shear injury is a common traumatic brain injury, with significant neurologic and behavioral impact on patients. Radiologic recognition of this entity and understanding of its sequelae can be of utmost importance in the prediction of outcome and planning for rehabilitation. MRI has proven to be the optimal means of detection and characterization of DAI lesions, with GRE and FLAIR sequences being particularly helpful, and more advanced techniques such as MRS show preliminary evidence of some utility in determining outcome.
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In addition to its inability to predict pressure elevation accurately, head CTs done serially even at 12-hour intervals, cannot adequately portray the dynamic, sometimes rapid evolution (usually growth) of a traumatic hematoma. These limitations aside, CT scanning provides adequate imaging for rational surgical treatment of head injury. Whether for monitoring, diagnostic, or therapeutic purposes, cranial procedures for traumatic pathology are guided by CT.
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Diffusion MR imaging provides unique information about the physiologic state of ischemic tissue. It is highly sensitive and specific in the detection of acute and hyperacute ischemic stroke and has greatly improved the diagnosis and treatment of acute stroke. ⋯ Diffusion combined with perfusion MR imaging provides information about the operational ischemic penumbra and final infarct size. Diffusion MR imaging seems to be promising in the evaluation of candidates for thrombolysis.
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Diffusion-weighted imaging is of limited value in the MR imaging diagnosis of various tumor pathologies, except in differentiating between dermoids/epidermoids and arachnoid cysts. Diffusion tractography, on the other hand, allows accurate depiction of important white-matter tracts adjacent to brain tumors. This technique uses data derived from diffusion tensor imaging.
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Spinal cord DWI may be useful in providing information not available with conventional MR imaging. More work, however, is required to explain what the qualitative and quantitative results actually represent. Computer simulations and detailed radiologic-histologic correlations will therefore be necessary.