Clinical Context
A 62-year-old patient presents to the emergency department with acute-onset severe focal neurological deficit and severe headache. The emergency physician suspects an intracranial vascular event such as ischemic stroke, subarachnoid hemorrhage, or large-vessel occlusion. After initial stabilization and evaluation, the patient is referred for computed tomographic angiography of the head and neck to evaluate arterial and venous vasculature, identify vessel occlusion, stenosis, aneurysm, dissection, or vascular malformation. The imaging study is performed in the CT angiography suite or hospital radiology department. Intravenous iodinated contrast is administered via power injector; noncontrast head CT images may be obtained immediately before CTA when indicated (for example, to exclude acute hemorrhage). The technologist acquires the CTA with thin-section helical technique and timing bolus or automated bolus tracking; the radiologist performs computer-based postprocessing (including 3D reconstructions and maximum intensity projections) and interprets the study, generating a report that documents vessel patency, stenosis percentage if present, aneurysm size and location, arterial dissection, and any acute infarct or hemorrhage seen on noncontrast images. Clinical workflow includes order entry with indication, screening for contrast allergy and kidney function, IV placement, image acquisition, postprocessing, radiologist interpretation, and communication of critical results to the treating team.