How soon after arrival in the emergency department should a patient with a suspected stroke have a computed axial tomography (CAT) scan of the brain?

Brain CT Timing for Suspected Stroke in the Emergency Department

For patients with suspected stroke arriving in the emergency department, the CT scan should be completed within 25 minutes of arrival and interpreted within 45 minutes (door-to-interpretation time of 45 minutes total). 1, 2

Critical Time Targets

The American Heart Association establishes specific benchmarks for acute stroke imaging that directly impact mortality and functional outcomes:

• CT completion: ≤25 minutes from ED arrival 1, 2
• CT interpretation: ≤45 minutes from ED arrival (total door-to-interpretation time) 1, 2
• Overall evaluation and treatment decision: ≤60 minutes from ED arrival 1

These targets are specifically designed for patients who may be candidates for thrombolytic therapy (rtPA), where every minute of delay increases brain tissue loss and worsens outcomes. 1

Why This Timing Matters for Patient Outcomes

The 25-minute CT completion target exists because thrombolytic therapy must be administered within 3-4.5 hours of symptom onset to reduce mortality and disability. 1, 2, 3 The narrow therapeutic window means that imaging delays directly translate to:

• Reduced eligibility for life-saving thrombolytic therapy 2, 3
• Larger final infarct volumes and worse functional outcomes 1
• Increased risk of hemorrhagic transformation if treatment is delayed 1

Research demonstrates that EMS prenotification and organized stroke protocols significantly improve adherence to these time targets, with prenotified patients being 3 times more likely to achieve the 25-minute CT completion goal. 4

Implementation Requirements

To achieve these time targets, hospitals must establish:

• Organized stroke team protocols with designated physicians, nurses, and radiology personnel available 24/7 1
• Immediate CT scanner access without delays for scheduling or patient transport 1
• Rapid interpretation capability by physicians with stroke imaging expertise 1
• Parallel processing where clinical assessment, laboratory studies, and imaging occur simultaneously rather than sequentially 1, 3

Advanced Imaging Considerations

Multimodal imaging (CT angiography, perfusion CT, or MRI) should NOT delay the initial non-contrast CT or administration of IV thrombolytic therapy in eligible patients. 2, 3, 5

• CT angiography from aortic arch to vertex can be performed at the time of initial brain CT to identify large vessel occlusions for potential endovascular therapy 1, 2, 3
• However, obtaining these additional studies must not push the door-to-needle time beyond optimal windows 2, 5
• Advanced imaging is most appropriate when performed in parallel with thrombolytic preparation, not as a sequential step 2, 5

Common Pitfalls to Avoid

Delaying CT for advanced imaging studies is the most critical error, as it eliminates thrombolytic eligibility for time-sensitive patients. 2, 5 Even a 10-minute delay in door-to-CT time significantly reduces the proportion of patients who can receive treatment within optimal windows. 4, 6

Waiting for complete laboratory results before obtaining CT imaging unnecessarily delays diagnosis—blood samples should be drawn but imaging should proceed immediately while results are pending. 1, 3

Performing chest x-rays or other non-essential studies before brain imaging is contraindicated, as most stroke patients do not require chest x-ray as part of initial evaluation. 1

Inadequate blood pressure control before imaging can delay thrombolytic eligibility—blood pressure must be reduced to <185/110 mmHg before rtPA administration, and this process should begin during the imaging phase. 1, 3

Quality Improvement Data

Implementation of direct-to-CT protocols (where EMS transports patients directly to the scanner upon ED arrival) has demonstrated:

• 10-minute reduction in median door-to-CT times 6
• 22% increase in patients treated within 45 minutes of arrival (84% vs 62%) 6
• 3-fold improvement in meeting the 25-minute CT completion target with EMS prenotification 4

These protocol-driven improvements directly translate to better functional outcomes and reduced mortality by maximizing the number of patients who receive time-sensitive interventions. 4, 6