The Relation of Carotid Calcium Volume with Carotid Artery Stenosis in Symptomatic Patients

H.A. Marquering; C.B.L.M. Majoie; L. Smagge; A.G. Kurvers; H.A. Gratama van Andel; R. van den Berg; P.J. Nederkoorn

doi:10.3174/ajnr.A2519

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Fig 1.
Illustration of the calcium volume measurement according to the method of McKinney et al.⁸ First, the carotid bifurcation is sculpted (left). After further adjustment of the window level and width, only the calcium is displayed (right). With the volume calculation tool, the calcium volume is displayed.
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Fig 2.
Scatterplot showing all measurements for the symptomatic and asymptomatic ICAs. The stenosis categories are illustrated with the gray vertical lines.
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Fig 3.
ROC curves for various calcium volume−based degrees of stenosis determination, illustrating the sensitivity and false-positive rate (1-specificity) for the tests. The best possible test yields a point in the upper left corner; a random guess gives a point along the diagonal line. The higher the curve is from the diagonal, the better the prediction test. This figure illustrates that the performance of the calcium volume−based stenosis determination decreases with increasing stenosis degree.
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Fig 4.
VR and MPR reconstructions showing a severe stenosis of 75% according to the NASCET criteria. B shows a display of calcium of the same bifurcation as in A. Total calcium volume is 0.01 mL.
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Fig 5.
VR and MPR reconstructions showing a low-level stenosis of 29% according to the NASCET criteria. B is a display of calcium of the same bifurcation as Fig 4A. Total calcium volume is 0.55 mL.

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Table 1:

Calcium volume for stenosis degree groups^a

Stenosis Categories	Group Size (Symptomatic)	Average Calcium Volume (mL)
Stenosis Categories	Group Size (Symptomatic)	Symptomatic	Asymptomatic	All
Minimal (0%–29%)	49 (8)	0.05 (± 0.06)	0.05 (± 0.07)	0.05 (± 0.06)
Mild (30%–49%)	29 (10)	0.11 (± 0.17)	0.08 (± 0.10)	0.09 (± 0.12)
Moderate (50%–69%)	40 (22)	0.12 (± 0.13)	0.17 (± 0.16)	0.14 (± 0.14)
Severe (70%–99%)	28 (20)	0.15 (± 0.19)	0.13 (± 0.17)	0.15 (± 0.19)
Occlusion	13 (7)	0.02 (± 0.03)	0.07 (± 0.12)	0.04 (± 0.09)
All	159 (67)	0.11 (± 0.15)	0.09 (± 0.12)	0.10 (± 0.13)

a In the second column, the number of arteries per category is given. The number of arteries that are labelled “symptomatic side” is given in parentheses. Columns 3–5 give the average calcium volume per artery. The SD is given in parentheses.

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Table 2:

Average calcium volume, stenosis degree, correlation for symptomatic and asymptomatic arteries, and the combination of both^a

	Pearson Correlation (Significance)	Average Calcium Volume (mL)	Average Degree of Stenosis (%)	Group Size
Symptomatic	0.04 (0.7)	0.11 (± 0.15)	61 (± 26)	67
Asymptomatic	0.29 (0.005)	0.09 (± 0.12)	37 (± 30)	92
All	0.20 (0.012)	0.10 (± 0.13)	47 (± 31)	159

a The second column displays the Pearson correlation coefficient relating the stenosis degree with the calcium volume. The significance is given in parentheses. The average calcium volume is displayed in the third column with the SD in parentheses. The fourth column shows the average degree of stenosis of the arteries with its SD shown in parentheses.

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Table 3:

Performance of the calcium volume test determining a stenosis degree of ≥40%^a

	Calcium Volume Threshold = 0.03 mL			Calcium Volume Threshold = 0.09 mL
	Symptomatic	Asymptomatic	All	Symptomatic	Asymptomatic	All
Sensitivity	63% (49%–74%)	66% (50%–79%)	64% (54%–73%)	48% (36%–61%)	45% (30%–60%)	47% (37%–57%)
Specificity	73% (43%–90%)	48% (35%–61%)	52% (40%–64%)	73% (43%–90%)	83% (71%–91%)	82% (70%–89%)
PPV	92% (79%–97%)	47% (34%–60%)	66% (56%–75%)	90% (74%–97%)	65% (46%–81%)	79% (66%–87%)
NPV	28% (15%–46%)	67% (51%–79%)	50% (38%–62%)	22% (11%–37%)	68% (56%–78%)	51% (42%–61%)

a The test was performed for a calcium-volume threshold of 0.03 mL (left) and 0.09 mL The 95% confidence interval is given in parentheses.

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Table 4:

Performance of the calcium volume test determining a stenosis degree of ≥50%^a

	Calcium Volume Threshold = 0.03 mL			Calcium Volume Threshold = 0.09 mL
	Symptomatic	Asymptomatic	All	Symptomatic	Asymptomatic	All
Sensitivity	65% (50%–77%)	65% (47%–79%)	65% (54%–74%)	48% (34%–62%)	45% (29%–62%)	47% (36%–58%)
Specificity	63% (41%–81%)	46% (34%–58%)	50% (39%–61%)	63% (41%–81%)	80% (69%–88%)	76% (66%–84%)
PPV	82% (67%–91%)	38% (26%–51%)	56% (46%–66%)	77% (59%–88%)	54% (35%–71%)	66% (53%–77%)
NPV	41% (26%–59%)	72% (56%–83%)	59% (47%–70%)	32% (20%–49%)	74% (63%–83%)	59% (50%–68%)

a The test has been performed for a calcium volume threshold of 0.03 mL (left) and 0.09 mL (right). The 95% confidence interval is given in parentheses.

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Table 5:

Performance of the calcium volume test determining a stenosis ≥70%^a

	Calcium Volume Threshold = 0.09 mL
	Symptomatic	Asymptomatic	All
Sensitivity	41% (25%–59%)	29% (12%–55%)	37% (24%–52%)
Specificity	53% (37%–67%)	72% (61%–81%)	65% (56%–73%)
PPV	37% (22%–54%)	15% (6%–34%)	27% (17%–40%)
NPV	57% (41%–71%)	85% (74%–92%)	7%5 (66%–82%)