Noncontrast computed tomography (NCCT) plus computed tomography angiography (CTA) is the standard imaging modality for acute stroke. We investigated whether there is an additional diagnostic value of supra-aortic CTA in relation to National Institutes of Health Stroke Scale (NIHSS) and resultant effective radiation dose.

In this observational study, 788 patients with suspected acute stroke were included and divided into 3 NIHSS groups: group 1, NIHSS 0–2; group 2, NIHSS 3–5; and group 3, NIHSS ≥ 6.

Computed tomography scans were assessed for findings of acute ischemic stroke and vascular pathologies in 3 regions. Final diagnosis was obtained from medical records. Effective radiation dose was calculated based on the dose-length product.

Seven hundred forty-one patients were included. Group 1 had 484 patients, group 2 had 127 patients, and group 3 had 130 patients. Computed tomography diagnosis of acute ischemic stroke was made in 76 patients. In 37 patients, a diagnosis of acute stroke was made based on pathologic CTA findings in case of an unremarkable NCCT. Stroke occurrence was the lowest in groups 1 and 2, with 3.6% and 6.3%, respectively, compared with 12.7% in group 3. If both NCCT and CTA were positive, the patient was discharged with a stroke diagnosis. Male sex had the highest effect on the final stroke diagnosis. The mean effective radiation dose was 2.6 mSv.

In female patients with NIHSS 0–2, additional CTA rarely contains relevant additional findings decisive for treatment decisions or overall patient outcomes; therefore, CTA in this patient group might yield less impactful findings, and the applied radiation dose could be lowered by approximately 35%.