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AJNR - American Journal of Neuroradiology

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Evaluation of Carotid Artery Stenosis with Multisection CT and MR Imaging: Influence of Imaging Modality and Postprocessing

M. Lell^a, C. Fellner^d, U. Baum^a, T. Hothorn^b, R. Steiner^a, W. Lang^c, W. Bautz^a and F.A. Fellner^e

^a Institute of Diagnostic Radiology, University Erlangen-Nuremberg, Erlangen, Germany
^b Departments of Medical Informatics, Biometry, and Epidemiology, University Erlangen-Nuremberg, Erlangen, Germany
^c Vascular Surgery, University Erlangen-Nuremberg, Erlangen, Germany
^d Institute of Radiology, Landes-Nervenklinik Wagner Jauregg, Linz, Austria
^e Institute of Radiology, AKh Linz, Linz, Austria

View larger version (10K): [in this window] [in a new window]   Fig 1. Variability of stenosis values between 2 observers for the different imaging and evaluation techniques assessed by scatterplots and ICC values showing excellent agreement between the observers.

View larger version (11K): [in this window] [in a new window]   Fig 2. Comparison of modalities by differences between stenosis values. Pairs of modalities that cross the zero-line are not considered significantly different. In cases of local signal intensity loss, the grade of stenosis was assigned as 90%. On average, stenosis values obtained with CE-MRA and MIP postprocessing were 7% higher than those with CTA. Stenosis values of TOF-MRA with MPR postprocessing were comparable with CTA.

View larger version (13K): [in this window] [in a new window]   Fig 3. Stenosis values for CTA, CE-MRA, and TOF-MRA evaluated with the MPR method are represented graphically in scatter plots (upper row) and Bland-Altman-plots (lower row). Confidence intervals of the difference in stenosis values are given as gray bands. Highest agreement is found for CTA and TOF-MRA. In cases of local signal loss, the grade of stenosis was assigned as 90%.

View larger version (110K): [in this window] [in a new window]   Fig 4. Stenosis of the left ICA. Local signal intensity loss at CE-MRA (A) with distal enhancement, but residual signal intensity is detectable with TOF-MRA (B: TOF-MIP) and CTA (C, "scout" MIP; D, transverse MPR at site of minimal lumen; E, transverse MPR at reference site beyond poststenotic dilation). Signal intensity is fading at the edge of the scan volume (B), leading to artificial lumen reduction on MIP images (B).