Which imaging modality is primarily used to differentiate between ischemic and hemorrhagic stroke?

The primary imaging modality used to differentiate between ischemic and hemorrhagic stroke is a CT scan. This is because a CT scan provides quick and effective visualization of the brain, allowing for the identification of acute hemorrhages and other acute changes that indicate bleeding. Ischemic strokes, which are caused by disruptions in blood flow, typically do not show immediate changes on a CT scan, but the absence of blood in the brain points toward this type of stroke.

CT scans are widely available, can be performed rapidly, and are particularly valuable in emergency settings where time is critical for treatment decisions. Their effectiveness in ruling out hemorrhagic stroke before administering thrombolytic therapy for ischemia underscores their importance in acute stroke management.

Other imaging techniques like MRI, while more detailed for identifying ischemic changes or determining tissue viability, are not usually the first line in acute stroke evaluation due to longer acquisition times and availability issues. X-rays do not provide adequate information about brain tissue or acute vascular changes, and ultrasounds are primarily used for assessing blood flow in the carotid arteries rather than imaging the brain itself.