Abstract WP165: Contrast Enhanced MR Angiography Overestimates Carotid Stenosis Compared With Time-of-Flight MR Angiography and Digital Subtraction Angiography

Abstract

Background: Contrast-enhanced magnetic resonance angiography (CEMRA) has begun to replace time-of-flight magnetic resonance angiography (TOFMRA), because it reduces imaging time and improves signal-to-noise ratio. However CEMRA might overestimate the degree of arterial stenosis. Objectives: With digital subtraction angiography (DSA) as reference standard, we tried to find out if CEMRA overestimates carotid artery stenosis more than TOFMRA. Methods: From April, 2013 to August, 2015, fifty six consecutive patients underwent TOFMRA, CEMRA and DSA. The degree of stenosis was measured using NASCET (North American Symptomatic Carotid Endarterectomy Trial) method and classified as mild (1~49%), moderate (50~69%), and severe (70~99%). Results: Six patients were excluded because of the poor quality of images. In 100 carotid arteries of 50 patients, 23 arteries had various degree of stenosis, 8 were occluded, and 69 were normal. CEMRA overestimated the severity of carotid stenosis in 8 out of 92 but TOFMRA did in 3 out of 92. We calculated the agreement by κ in CEMRA vs. DSA (κ = 0.79, p < 0.05) and TOFMRA vs. DSA (κ= 0.92, p < 0.05). For detection of severe stenosis, CEMRA had the sensitivity of 100% and the specificity of 90% while TOFMRA had 100% and 97.5% respectively. The rate of misclassification of patients as an appropriate candidate for carotid endarterectomy (CEA) was 40.4% in CEMRA and 14.8% in TOFMRA. Conclusion: CEMRA has some advantages over TOFMRA but it tends to overestimate the severity of carotid stenosis. The results of CEMRA should be compared with those of TOFMRA or DSA when surgical intervention is considered.