HOW SHOULD WE ESTIMATE CAROTID STENOSIS USING MAGNETIC-RESONANCE ANGIOGRAPHY

Our purpose was to assess the reproducibility of and differences betwe en the most commonly used methods for assessing carotid artery stenosi s using magnetic resonance angiography (MRA). We studied 55 patients w ho underwent axial three-dimensional time-of-flight MRA (1.5 T). Quant itative caliper measurements were performed from maximum intensity pro jection (MZP) and multiple planar reconstruction (MPR) images, accordi ng to the criteria of the North American Symptomatic Carotid Endartere ctomy Trial (NASCET) and European Carotid Surgery Trial (ECST). The me asurements were compared to each other and to visual interpretation, u sing conventional angiography as the reference. The measured percentag e stenoses were higher on MRA than on digital subtraction angiography (DSA) using both NASCET (mean difference 1.9-3.0 %) and ECST (6.3-6.7 %) criteria. The kappa coefficients for the agreement between DSA and MRA were higher using the NASCET (0.61-0.76) than the ECST criteria (0 .52-0.65). No statistically significant differences were found between measurements from MIP and MPR images. The ECST measurement criteria g ave significantly higher percentage stenoses than the NASCET criteria (P < 0.001), this difference being more prominent on MRA (mean differe nce in diameter stenosis percentage 14.3-16.4 %) than on DSA (7.6-11.2 %) and most important with mild stenoses. The difference between visu al interpretation and quantitative measurements on MRA was significant (P = 0.01-0.001). There were no statistically significant interobserv er differences in the MRA film readings, either in visually estimated degrees of stenosis or stenosis measurements. Thus, the different crit eria of the two multicentre trials led to significantly different resu lts, especially in the assessment of mild stenosis, and these differen ces are more important with MRA than with DSA. Differences between the imaging modalities or the reconstruction programs seem less important .