See related article, pages 3511–3517. Wardlaw and colleagues1 use modeling to validate noninvasive imaging instead of intra-arterial angiography (IAA) for carotid stenosis. They conclude that duplex ultrasound (DUS) is best. There are not sufficient data with CT angiography (CTA) and MR angiography. Yet carotid CTA gives excellent anatomic depiction, has no stroke risk, and takes a few seconds more than simple CT.2–4⇓⇓ It adds to CT for emergency cases in acute stroke protocols and is done 24 hours a day as a regular CT service. CTA already replaced much of diagnostic IAA. Contrast CT is a common CT technique and CTA is merely scanning during contrast infusion. Its anatomic exactness for stenosis quantification is accepted as anatomically correct,2–12⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓ yet published data are insufficient for modeling needed for Wardlaw and colleagues.1 IAA had no scientific verification of arterial anatomic depiction; instead, there was excitement and acceptance that arteries look like arteries. CTA now gives anatomically correct images without stroke risk. Sites expert in CTA face ethical dilemmas against continuing stroke-risk IAA to quantify stenosis for clinical or research purposes. CTA includes inherent millimeter measurements, not part of standard IAA digital subtraction angiography measured in pixels.13 Because CTA studies were not adequate to plug into Wardlaw and colleagues’ models, CTA was only considered in a limited way for Wardlaw and colleagues’ model. In the 1990s, some stopped doing IAA for carotid …