Carotid Stenosis (NASCET & ECST)
NASCET (1991) / ECST (1998) diameter methodsComputes percent ICA stenosis by the NASCET method (residual lumen vs normal distal ICA) and the ECST method (residual lumen vs estimated bulb diameter).
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Information
Incomplete input
- Enter measurement A (narrowest residual lumen, in mm).
How this tool works
Diameter-based angiographic grading expresses carotid stenosis as a percentage of luminal narrowing. The NASCET method compares the narrowest residual lumen (A) with the diameter of the normal distal cervical internal carotid artery where the walls run parallel (B): stenosis = (1 - A/B) x 100. The ECST method instead references the estimated original diameter of the carotid bulb at the lesion site (C): stenosis = (1 - A/C) x 100, which yields higher percentages for the same lesion. Severity bands are conventionally reported as mild (<50%), moderate (50-69%), severe (70-99%), and occlusion. In the NASCET trial, symptomatic patients with 70-99% stenosis derived clear benefit from endarterectomy, with a more modest, subgroup-dependent benefit at 50-69%; in ECST the corresponding surgical threshold was approximately 80%.
References
- NASCET Collaborators. Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis. N Engl J Med. 1991;325:445-453
- Radiopaedia: carotid artery stenosis grading (NASCET/ECST methods and bands)
Implemented from the cited published sources. Educational use only; confirm against current guidelines before clinical use.
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