A Brief Overview about Possible Imaging Modalities of Stroke

Abstract

Background: NCCT is the main imaging modality for the initial evaluation of patients with suspected stroke, allowing clinicians to identify hemorrhage, which produces a good contrast between the “bright”, high attenuating clot, and the “dark” low attenuating cerebrospinal fluid . This is crit- ical in selecting patients for intravenous thrombolysis (IVT) via tissue plasminogen activator (t-PA) within 4.5 hours since hem- orrhage is an absolute contraindication and must be excluded . Moreover, the presence of various early ischemic changes (EIC), including parenchymal hypoattenuation, cortical sulcal effacement , and loss of grey-white matter differentiation may be visualized up to 6 hours from symptom onset and inform treatment decisions. CT angiography (CTA) is a bolus contrast tracking technique that can be used to visualize the macrovasculature from the aortic arch to the cranial vertex within 15 s . Spatial resolution is excellent and in fact superior to most clinical magnetic resonance angiography sequences. In conventional CTA, an optimal intravenous contrast bolus profile consists of a rapid rise, plateau of peak enhancement, followed by a rapid fall. Scan acquisition is triggered by contrast bolus-arrival in the aortic arch, which is designed to capture images at the peak arterial enhancement phase . Multiphase CT angiography (mCTA) was developed in an attempt to obtain temporal information by tracking the bolus beyond the peak arterial phase . By repeating the CT acquisition in 1 mm slice increments following a delay of 7–8 s and another 7–8 s, images of the vasculature in the late arterial and venous phases can be obtained.