Noncontrast CT, CTA, Perfusion, and Imaging Workflow
Key Takeaways
- Noncontrast brain CT or MRI is the first imaging gate because thrombolytic therapy cannot proceed until intracranial hemorrhage is excluded.
- Early ischemic stroke can have a normal noncontrast CT, so a normal early scan does not rule out disabling ischemia.
- CTA from the aortic arch through the head helps identify large-vessel occlusion and supports thrombectomy routing or transfer decisions.
- CT perfusion or MRI mismatch imaging can identify infarct core and salvageable tissue for selected patients with wake-up stroke, unknown onset, or later presentation.
- The nurse improves imaging speed by preparing monitoring, IV access, contrast screening, transport, last-known-well data, and closed-loop communication before the scanner is ready.
Imaging answers the first safety question
The first imaging question in suspected acute stroke is whether bleeding is present. A noncontrast computed tomography (CT) scan is fast and widely available, so it is commonly used to exclude intracranial hemorrhage before thrombolytic therapy. MRI can also exclude hemorrhage and detect early ischemia, but it is usually less available for immediate code-stroke workflow.
Do not overinterpret a normal early CT. Ischemic changes may be subtle or absent in the first hours. The scan may show no hemorrhage while the patient still has disabling ischemic stroke. The correct nursing response is to keep the stroke pathway moving, not to reassure the patient that a normal CT means nothing is wrong.
Time goals are system goals
Get With The Guidelines and Target: Stroke measures track steps such as brain imaging within 20 or 25 minutes, CT or MRI interpretation within 45 minutes in rural recognition measures, and door-to-needle within 60 minutes for treated patients. SCRN questions are unlikely to ask the nurse to memorize every registry field, but they often test the behavior behind those metrics: EMS prenotification, single-call activation, direct-to-CT transport, parallel lab collection, and early pharmacy involvement.
| Imaging step | Main purpose | Nursing contribution |
|---|---|---|
| Noncontrast CT | Exclude hemorrhage and major established infarct | Rapid transport, monitoring, safety, LKW communication |
| CTA head and neck | Identify large-vessel occlusion and vascular anatomy | IV access, contrast allergy screen, kidney-risk history per protocol |
| CT perfusion | Estimate infarct core and penumbra | Keep patient still, communicate onset uncertainty, relay results quickly |
| MRI DWI/FLAIR | Detect early ischemia and mismatch in selected cases | Screen for MRI safety and avoid delays when CT pathway is preferred |
| Repeat imaging | Evaluate deterioration or post-treatment bleeding | Escalate change and prepare urgent transport |
CTA and large-vessel occlusion
A patient with aphasia, gaze deviation, dense hemiparesis, neglect, or decreased consciousness may have a large-vessel occlusion (LVO). CTA from the aortic arch through the vertex can identify occlusion location and supports decisions about endovascular thrombectomy. The nurse does not decide thrombectomy eligibility independently, but should recognize why vascular imaging and transfer calls are urgent.
Contrast questions are practical nursing questions. Verify allergies, prior contrast reaction, IV adequacy, and known kidney disease according to local protocol. At the same time, do not let low-yield paperwork or nonurgent history collection delay imaging when the team has accepted the risk-benefit plan.
Perfusion and extended windows
Perfusion imaging helps estimate infarct core and ischemic penumbra. Core is tissue already likely infarcted; penumbra is at-risk tissue that may still be salvageable. In selected patients with wake-up stroke, unknown onset, or presentation beyond the standard early window, advanced imaging may identify patients who can still benefit from reperfusion therapy.
The 2026 AHA/ASA update supports advanced-imaging selection for some patients with unknown onset or 4.5 to 9 hours from onset, and broader endovascular eligibility for selected patients. For the SCRN nurse, the key is not to quote trial names at the bedside. The key is to keep LKW, discovery time, neurologic severity, baseline function, and imaging results connected so the stroke specialist can make a rapid decision.
Nursing workflow in the scanner
Before transport, confirm monitoring needs, IV access, glucose, vital signs, and airway stability. During imaging, watch for vomiting, agitation, worsening mental status, or need for airway support. After imaging, make sure results reach the decision-makers immediately. A scan that is completed but not communicated has not helped the patient.
A family member asks why the patient needs a CT scan before thrombolytic medication. Which explanation is best?
A patient has gaze deviation, aphasia, and dense right hemiparesis. Noncontrast CT shows no hemorrhage. Which imaging study most directly supports thrombectomy decision-making?
A patient arrives 7 hours after last known well. CT shows no hemorrhage, CTA shows an M1 occlusion, and perfusion imaging suggests a small core with substantial penumbra. What should the nurse anticipate?