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Carotid stenosis degree in CT angiography: assessment based on luminal area versus luminal diameter measurements

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The aim of this study was to investigate CT angiography (CTA) luminal area measurements in the assessment of carotid artery stenosis compared with the current clinically used criteria based on lumen diameter measurements. Seventy-two vessels in 36 patients were evaluated by CTA and digital subtraction angiography (DSA). Two observers measured area and diameter stenosis degrees using automated 3D CTA analysis software. The ratio of the largest/smallest luminal diameter at the level of maximal stenosis (L/S ratio) was used to describe lumen morphology. Diagnostic agreement between CTA and DSA was calculated. For the assessment of area stenosis, interobserver and intraobserver correlation coefficients were 0.898 and 0.906 (p<0.001). The correlation coefficient between the diameter stenosis and area stenosis was lower in stenoses with extremely noncircular lumen (L/S ratio ≥1.5) (r=0.797, p<0.001) compared with stenoses with circular lumen (LS ratio <1.2) (r=0.978, p<0.001). Only satisfactory agreement (κ 0.54-0.77, p<0.001) was obtained between area stenosis on CTA and diameter stenosis on DSA. Assessment of stenosis degree with area measurements on 3D CTA proved to be reproducible. Area stenosis provides a less-severe estimate of the degree of carotid stenosis but might theoretically express the real hemodynamic significance of the lesion better than diameter stenosis, especially in stenoses with noncircular lumen.

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This work was supported by a grant from Kuopio University Hospital (grant number 5063501).

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Correspondence to Marja Berg.



1. The theoretical (standard) equation between area stenosis and where r2: radius of reference area; r1: radius of maximal stenosis area; A: area stenosis degree; N: diameter stenosis degree.

The equation A=2N-N2 is valid when carotid lumens are circular in shape (L/S ratio=1.0) both at the level of maximal stenosis and at the level of reference. Thus for 70%, 50%, and 30% diameter stenosis, the corresponding area stenosis values are 91%, 75%, and 51%, respectively.

2. The regression curve between area stenosis and diameter stenosis by 3D AVA in this study:

$$A = 2.869 + 1.160*N - 0.002*N^{2} $$

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Zhang, Z., Berg, M., Ikonen, A. et al. Carotid stenosis degree in CT angiography: assessment based on luminal area versus luminal diameter measurements. Eur Radiol 15, 2359–2365 (2005).

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