Carotid Stenosis Index Revisited With Direct CT Angiography Measurement of Carotid Arteries to Quantify Carotid Stenosis

Abstract

Background and Purpose— All carotid stenosis ratio methods are based on the inability of digital subtraction angiography to measure in millimeters. Each method has potential flaws. The Carotid Stenosis Index (CSI) was designed to reduce ambiguities of NASCET and ECST ratios. We test this method’s ability to correctly estimate carotid stenosis using direct computed tomography angiography millimeter measures of the carotid arteries. Methods— Two neuroradiologists reviewed computed tomography angiographies of 268 carotids with atherosclerotic disease. Millimeter measurements were obtained at the narrowest diameter of the residual stenotic lumen, actual carotid bulb diameter (at level of greatest stenosis), and common carotid artery. Pearson correlation compared the CSI estimate of the carotid bulb to the actual carotid bulb measurement. Ratio calculations of the stenosis were performed using (1) CSI carotid bulb estimate and (2) actual carotid bulb measurement as denominator data. A paired-sample Wilcoxon signed rank test compared the results of these 2 ratio measurements per carotid. Results— Interobserver variability was good to excellent (0.64 to 0.87). The CSI estimate of the carotid bulb size overestimated the measured carotid bulb by an average of 1.5 mm in a random distribution (correlation=0.39, N=151). Paired-sample Wilcoxon signed rank test demonstrated a significant difference between the 2 sets of ratios (z-value of −9.87, P <0.001). Conclusions— Direct measurement of carotid stenosis, vessel wall soft tissues, and computed tomography plaque imaging is now possible with the high-resolution anatomic data present in high-speed computed tomography angiography, alleviating the need for ratios and inaccurate mathematic estimations of carotid anatomy for carotid stenosis quantification.

Role of CT Angiographic Plaque Morphologic Characteristics in Addition to Stenosis in Predicting the Symptomatic Side in Carotid Artery Disease

“…Plaque characteristics such as lipid-rich core, fibrous cap thickness, and intraplaque hemorrhage have been demonstrated on sonography [4][5][6] and MR imaging, [7][8][9][10][11][12][13][14][23][24][25] and it is suggested that these ancillary features, taken in conjunction with the degree of stenosis, may be important predictors of future stroke risk. CT angiography is being increasingly used to noninvasively image carotid stenosis 26,27 and has also been shown to be useful in the evaluation of carotid plaque morphology. 15,17,[28][29][30][31] The findings from our study indicate that apart from increasing degree of stenosis, the presence of an intraluminal thrombus is highly predictive of the symptomatic side in patients with carotid disease.…”

MR Imaging: Influence of Imaging Technique and Postprocessing on Measurement of Internal Carotid Artery Stenosis

“…Multiplanar reformation of MRA data can solve this problem by aligning the image plane perpendicular to the ICA to optimize measurement of eccentric stenosis. 30 The disadvantages of MPR evaluation are the inferior 3D visualization of the vessels and higher time demand to adjust the image planes. Volume-rendering techniques optimally visualize vessels in 3 dimensions, but the parameter setting of the transfer function is critical for morphologic measurements.…”

Comparison of the Carotid Stenosis Index With CT Angiography

“…4 Bartlett et al have now harnessed the inevitable advances in imaging technology and have used computed tomography angiography (CTA) to directly measure carotid stenosis using screen calipers applied to contrast luminograms of the carotid bulb. 9 Their message seems to be that measurements of carotid stenosis should be direct and individualized, not generalized, by CTA measurement of the diameters of the carotid bulb and the atheromatous stenosis. However, CTA is not without technological difficulties.…”

“…As the authors note, using CTA indeed involves a new measurement paradigm for carotid stenosis. 9 The authors attempt at comparison with the CSI method falls short because of the methodology used. 9 Critically, the CTA measurements (carotid bulb stenosis and carotid bulb diameter) are made on contrast luminogram axial images at the level of tightest stenosis, ie, both the stenosis and the carotid bulb diameter are measured at the same location.…”

“…9 The authors attempt at comparison with the CSI method falls short because of the methodology used. 9 Critically, the CTA measurements (carotid bulb stenosis and carotid bulb diameter) are made on contrast luminogram axial images at the level of tightest stenosis, ie, both the stenosis and the carotid bulb diameter are measured at the same location. In contrast, the CSI method is designed to give an estimate of the carotid bulb diameter at the widest point of the carotid bulb, not at the tightest point of the stenosis.…”