Contrast-Enhanced MR Angiography Is Not More Accurate Than Unenhanced 2D Time-of-Flight MR Angiography for Determining ≥70% Internal Carotid Artery Stenosis

L.S. Babiarz; J.M. Romero; E.K. Murphy; B. Brobeck; P.W. Schaefer; R.G. González; M.H. Lev

doi:10.3174/ajnr.A1464

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Fig 1.
This ICA origin was rated by the observers to have severe (70%–95%) stenosis when imaged by all 3 techniques: 2D TOF MRA (A), CEMRA (B), and CTA (C–E). A and B, Signal-intensity drop-out is noted (arrow), but no distal narrowing or distal signal-intensity reduction is observed on MRA images. C, Curved reformatted CTA view of the left ICA demonstrating a severe stenosis (arrow). D, An axial image at the level of greatest narrowing (arrow). E, At the level of the NASCET reference diameter (arrow).
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Fig 2.
A scatterplot of stenosis scores on CE-MRA and 2D TOF MRA (A) and ROC curves for CE-MRA versus 2D TOF MRA (B). The size of the marker on the scatterplot represents the relative frequency of stenosis scores.
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Fig 3.
A, MRA of the neck with gadolinium demonstrating signal-intensity drop-out in the proximal left ICA (solid arrow), with decreased signal intensity and vessel narrowing (slim sign) in the distal ICA (dashed arrows), which is significantly smaller compared with the ipsilateral vertebral artery (double-tailed arrow). B, 2D TOF MRA image of the neck vasculature exemplifies distal-vessel narrowing/irregularity and distal-vessel signal-intensity reduction (white arrows).

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Table 1:

Comparison of CTA versus CE-MRA, CTA versus 2D TOF MRA, and CE-MRA versus 2D TOF MRA stenosis scores

Techniques	Difference
Techniques	None	By 1	By 2	By 3	By 4
CTA vs CE-MRA	265/354 (75%)	72/354 (20%)	13/354 (4%)	2/354 (0.5%)	2/354 (0.5%)
CTA vs 2D TOF MRA	227/354 (64%)	104/354 (29%)	20/354 (6%)	0/354 (0%)	3/354 (1%)
CE-MRA vs 2D TOF MRA	250/354 (71%)	85/354 (24%)	15/354 (4%)	3/354 (0.75%)	1/354 (0.25%)

Note:—CTA indicates CT angiography; CE-MRA, contrast-enhanced MR angiography; TOF MRA, time-of-flight MR angiography.

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Table 2:

Sensitivity, specificity, accuracy, PPV, and NPV of CE-MRA and unenhanced 2D TOF MRA for detection of ≥70% ICA stenosis* based on CTA reference measurements

Technique	Sensitivity	Specificity	Accuracy	PPV	NPV
CE-MRA	83.6% (46/55)	95.7% (286/299)	93.8% (332/354)	78.0% (46/59)	96.9% (286/295)
2D TOF MRA	80.0% (44/55)	95.3% (285/299)	92.9% (329/354)	75.9% (44/58)	96.3% (285/296)

Note:—PPV indicates positive predictive value; NPV, negative predictive value; ICA, internal carotid artery.
* Scores of 3 and 4.

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Table 3:

Sensitivity, specificity, accuracy, PPV, and NPV of signal drop-out, distal-vessel narrowing, and distal-vessel signal-intensity reduction for detection of ≥70% ICA stenosis* based on CTA reference measurements

	Sensitivity	Specificity	Accuracy	PPV	NPV
CE-MRA
Signal drop-out	65.5% (36/55)	98.3% (294/299)	93.2% (330/354)	87.8% (36/41)	93.9% (294/313)
Distal-vessel narrowing	41.8% (23/55)	99.3% (297/299)	90.4% (320/354)	92% (23/25)	90.3% (297/329)
Distal-vessel signal reduction	41.8% (23/55)	99.3% (297/299)	90.4% (320/354)	92% (23/25)	90.3% (297/329)
2D TOF MRA
Signal drop-out	50.9% (28/55)	98.7% (295/299)	91.2% (323/354)	87.5% (28/32)	91.6% (295/322)
Distal-vessel narrowing	34.5% (19/55)	99% (296/299)	89% (315/354)	86.4% (19/22)	89.2% (296/332)
Distal-vessel signal reduction	36.4% (20/55)	99% (296/299)	89.3% (316/354)	87% (20/23)	89.4% (296/331)