From the Guidelines
MRI is preferred over CT for diagnosing stroke when time permits, due to its superior soft tissue contrast and ability to detect ischemic strokes early, while CT is preferred in acute emergency settings due to its speed and ability to quickly rule out hemorrhagic stroke. The advantages of MRI include its ability to distinguish between acute, subacute, and chronic strokes through diffusion-weighted imaging (DWI) and detect small infarcts, especially in the posterior fossa and brainstem areas where CT has limitations 1. However, MRI has significant drawbacks, including longer performance time, higher cost, and limited availability in emergency settings 1. CT scanning, on the other hand, excels in emergency situations due to its speed, wider availability, and lower cost, making it crucial for quickly ruling out hemorrhagic stroke and determining if thrombolytic therapy can be administered 1. The choice between MRI and CT ultimately depends on timing, patient condition, and availability.
Some key points to consider when choosing between MRI and CT include:
- MRI offers superior soft tissue contrast and can detect ischemic strokes early, but takes longer to perform and is more expensive 1
- CT is faster and more widely available, but may not detect ischemic strokes as early as MRI 1
- MRI can distinguish between acute, subacute, and chronic strokes, while CT may not be able to make this distinction as easily 1
- CT is better at detecting acute bleeding and can be performed on unstable or uncooperative patients, making it preferred in acute emergency settings 1
In terms of specific patient populations, MRI may be preferred for patients with suspected stroke who are stable and can undergo a longer imaging procedure, while CT may be preferred for patients who are unstable or require rapid imaging to rule out hemorrhagic stroke 1. Ultimately, the choice between MRI and CT should be made on a case-by-case basis, taking into account the individual patient's needs and circumstances.
From the Research
Advantages of MRI over CT in Diagnosing Stroke
- MRI is more sensitive than noncontrast CT for differentiation of acute ischemic stroke from nonstroke conditions 2
- MRI detects acute stroke (ischaemic or haemorrhagic), acute ischaemic stroke, and chronic haemorrhage more frequently than CT 3
- MRI is better than CT for detection of acute ischaemia, and can detect acute and chronic haemorrhage 3
- MRI identifies a broader range of acute and chronic cerebrovascular pathologies than CT, which could aid decisions about acute intervention, in-hospital management, and secondary prevention 2
- Diffusion-weighted MRI has a much higher sensitivity for acute lesions than CT 4, 5
Disadvantages of MRI compared to CT in Diagnosing Stroke
- MRI may cause workflow delays of approximately 20 minutes compared to CT 6
- MRI is not always preferred due to initial resistance and technical problems, making CT still a commonly used tool 4
- CT is still the preferred imaging modality for patients with acute stroke in daily routine 5
Comparison of MRI and CT in Diagnosing Stroke
- Noncontrast CT and gradient-recalled echo MRI show comparable accuracy in the diagnosis of acute intracranial hemorrhage 2
- MRI and CT have similar detection rates for acute intracranial haemorrhage 3
- Combined multimodal parenchymal, perfusion and vascular imaging with CT or MRI has the potential to identify patients with an ischemic penumbra that might be appropriate for acute reperfusion therapies 2