The purposes of this study were 1) to correlate the carotid intima-medial thickness (IMT) with risk factors of atherosclerosis, 2) to demonstrate the standarized methods of B-mode ultrasound (US) scanning of carotid artery and IMT measurement.

Bilateral carotid arteries of 95 adult volunteers were scanned using 12 MHz linear probe. The mean of bilateral IMT was regarded as the volunteer's IMT, which was measured on the far wall of distal common carotid artery. The normality test for measured IMT and correlation tests between IMT and various known risk factors of atherosclerosis including age, end-systolic blood pressure, end-diastolic blood pressure, fasting blood glucose level, body mass index, life-style data and lipid profiles were performed. Inter-observer and intra-observer variability were evaluated through correlation tests on 20 randomly sampled data.

The measured IMT showed normal distribution (mean=0.673 mm, SD=±0.1, p=0.494) and the 95th percentile was 0.830 mm. The systolic blood pressure (r=0.101) and body mass index (r=0.200) showed positive correlation but they did not show statistically significant relationships with IMT (p>0.05). The age showed statistically significant correlation (r=0.585, p<0.001), but the other risk factors did not show statistically significant correlation with IMT. The correlation coefficients of inter-observer and intra-observer variability on IMT measurement were 0.8770 and 0.9213, respectively.

The diagnostic criteria for early carotid atherosclerosis using B-mode US could be estimated from our data. Our measurement protocols showed high reproducibility. The associations between most risk factors that did not show statistically significant correlation in our study and IMT should be confirmed in a population-based study.