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NASCET Percent Stenosis Semi-Automated Versus Manual Measurement on CTA

Published online by Cambridge University Press:  02 December 2014

Kevin Lian
Affiliation:
Division of Neuroradiology, Department of Medical Imaging, University of Toronto, Toronto, Ontario, Canada
Jeremy H. White
Affiliation:
Division of Neuroradiology, Department of Medical Imaging, University of Toronto, Toronto, Ontario, Canada
Eric S. Bartlett
Affiliation:
Division of Neuroradiology, Department of Medical Imaging, University of Toronto, Toronto, Ontario, Canada
Aditya Bharatha
Affiliation:
Division of Neuroradiology, Department of Medical Imaging, University of Toronto, Toronto, Ontario, Canada
Richard I. Aviv
Affiliation:
Division of Neuroradiology, Department of Medical Imaging, University of Toronto, Toronto, Ontario, Canada
Allan J. Fox
Affiliation:
Division of Neuroradiology, Department of Medical Imaging, University of Toronto, Toronto, Ontario, Canada
Sean P. Symons*
Affiliation:
Division of Neuroradiology, Department of Medical Imaging, University of Toronto, Toronto, Ontario, Canada
*
Division of Neuroradiology, Department of Medical Imaging, Sunnybrook Health Sciences Centre, University of Toronto, 2075 Bayview Avenue, AG31D, Toronto, Ontario, Canada, M4N 3M5. Email: [email protected]
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Abstract

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Purpose:

To compare North American Symptomatic Carotid Endarterectomy Trial (NASCET) stenosis values and NASCET grade categorization (mild, moderate, severe) of semi-automated vessel analysis software versus manual measurements on computed tomography angiography (CTA).

Methods:

There were four observers. Two independently analyzed 81 carotid artery CTAs using semi-automated vessel analysis software according to a blinded protocol. The software measured the narrowest stenosis in millimeters (mm), distal internal carotid artery (ICA) in mm, and calculated percent stenosis based on NASCET criteria. One of these two observers performed this task twice on each carotid, the second analysis was delayed two months in order to mitigate recall bias. Two other observers manually measured the narrowest stenosis in mm, distal ICA in mm, and calculated NASCET percent stenosis in a blinded fashion. The calculated NASCET stenoses were categorized into mild, moderate, or severe. Chi square and analysis of variance (ANOVA) were used to test for statistical differences.

Results:

ANOVA did not find a statistically significant difference in the mean percent stenosis when comparing the two manual measurements, the two semi-automated measurements, and the repeat semi-automated. Chi square demonstrated that the distribution of grades of stenosis were statistically different (p<0.05) between the manual and semiautomated grades. Semi-automated vessel analysis tended to underestimate the degree of stenosis compared to manual measurement.

Conclusion:

The mean percentage stenosis determined by semi-automated vessel analysis is not significantly different from manual measurement. However, when the data is categorized into mild, moderate and severe stenosis, there is a significant difference between semi-automated and manual measurements. The semi-automated software tends to underestimate the stenosis grade compared to manual measurement.

Type
Research Article
Copyright
Copyright © The Canadian Journal of Neurological 2012

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