From the Guidelines
Non-contrast CT scans are the first-line imaging test for suspected stroke because they can quickly rule out hemorrhagic stroke before administering thrombolytic therapy. This rapid assessment is crucial as tissue plasminogen activator (tPA) must be given within 4.5 hours of symptom onset for ischemic stroke but would be catastrophic if given to a patient with bleeding in the brain. Non-contrast CT can detect blood immediately, appearing as hyperdense areas, while also potentially showing early signs of ischemic stroke such as loss of gray-white matter differentiation, hypodense areas, or a hyperdense vessel sign indicating a clot. The scan takes only minutes to perform and interpret, requires no contrast agents that might cause allergic reactions or kidney problems, and is widely available in emergency departments 1.
Key Points
- Non-contrast CT is essential for the time-sensitive triage of stroke patients to determine appropriate treatment pathways.
- It can quickly rule out hemorrhagic stroke before administering thrombolytic therapy.
- The scan is widely available, quick to perform and interpret, and requires no contrast agents.
- While CT angiography and MRI provide more detailed information, the initial non-contrast CT remains the first-line imaging test for suspected stroke 1.
Imaging Protocol
The optimal imaging protocol for suspected acute ischemic stroke includes:
- Non-contrast head CT (NCCT) to rule out hemorrhage and roughly estimate the ischemic core.
- Multiphase CT angiography to detect and localize the occlusion, estimate treatment risks and benefits, and allow for procedural planning 1.
Clinical Decision-Making
For patients presenting within the 6-h timeframe, CTP is not necessary for clinical decision-making. However, for late-window patients, CTP or DWI may be used to determine ischemic core volumes and guide treatment decisions 1.
Treatment Considerations
The primary goal of imaging in acute stroke is to distinguish between hemorrhagic and ischemic stroke, and to guide treatment decisions, including the use of tPA and endovascular therapy 1. Non-contrast CT scans play a critical role in this process, and are essential for the rapid and accurate diagnosis of stroke.
From the Research
Non-Contrast CT for Stroke Testing
- Non-contrast head computed tomography (CT) is the most commonly used initial imaging tool to evaluate stroke, due to its sensitivity for hemorrhage, rapid acquisition, and widespread availability 2.
- The primary reason for using non-contrast CT in stroke testing is to exclude intracranial hemorrhage, as thrombolytic therapy is contraindicated in patients with hemorrhagic stroke 3, 4.
- Non-contrast CT can also directly visualize parenchymal changes of early infarct, although it has limited sensitivity and moderate interobserver variability in detecting early infarcts 4.
- Non-contrast CT can be used in combination with stroke severity to select patients for transfer to larger centers for evaluation and potential endovascular thrombectomy (EVT) 5.
- The use of non-contrast CT in stroke testing can help speed up and optimize management, providing early revascularization and reperfusion 6.
Advantages of Non-Contrast CT
- Rapid acquisition and widespread availability make non-contrast CT an ideal first study for stroke evaluation 2.
- Non-contrast CT is highly sensitive for hemorrhage, allowing for quick exclusion of intracranial hemorrhage 3, 4.
- Non-contrast CT can be used to identify patients who may benefit from EVT, even in small or rural hospitals with limited resources 5.