Stroke is the sudden onset of focal neurologic symptoms due to ischemia or hemorrhage in the brain. Current FDA-approved clinical treatment of acute ischemic stroke involves the use of the intravenous thrombolytic agent recombinant tissue plasminogen activator given <3 hours after symptom onset, following the exclusion of intracerebral hemorrhage by a noncontrast CT scan. Advanced MRI, CT, and other techniques may confirm the stroke diagnosis and subtype, demonstrate lesion location, identify vascular occlusion, and guide other management decisions but, within the first 3 hours after ictus, should not delay or be used to withhold recombinant tissue plasminogen activator therapy after the exclusion of acute hemorrhage on noncontrast CT scans. MR diffusion-weighted imaging is highly sensitive and specific for acute cerebral ischemia and, when combined with perfusion-weighted imaging, may be used to identify potentially salvageable ischemic tissue, especially in the period >3 hours after symptom onset. Advanced CT perfusion methods improve sensitivity to acute ischemia and are increasingly used with CT angiography to evaluate acute stroke as a supplement to noncontrast CT. The ACR Appropriateness Criteria(®) are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.
A double-blind, retrospective analysis of 110 sequentially operated parotid masses compared the usefulness of preoperative radiologic evaluation to histopathologic diagnosis. The radiologic assessment included 25 sialograms, 162 computed tomography scans, and 10 nuclear magnetic resonance images. The diagnosis is influenced by the following four parameters of computed tomography: tumor borders, density, homogeneity, and enhancement. Well-defined borders, a homogeneous appearance, and high density strongly favor the diagnosis of a benign tumor or a low-grade malignancy (96.7%). Ill-defined tumor borders, heterogeneity, and high density indicate mainly a high-grade or recurrent malignancy (68.8%). Ill-defined borders, a heterogeneous appearance, and mixed density identify a lymphoepithelial lesion, lymphangioma, or sialoadenitis (100%). Sialography is cost effective in the evaluation of lymphoepithelial lesions. Computed tomography sialography offers no advantages over computed tomography with intravenous contrast. High-resolution computed tomography with intravenous contrast is highly sensitive for tumor detection (97%). Magnetic resonance imaging is complementary or superior to computed tomography (100%).
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