Improved common carotid elasticity and intima-media thickness measurementsfrom computer analysis of sequential ultrasound frames

B-mode ultrasound has gained popularity as a non-invasive method for direct visualization of superficial vessels. With B-mode ultrasound, arterial sti ffness can be directly measured since image acquisition of the arterial wal l thickness and vessel diameter can be obtained simultaneously in a dynamic fashion throughout the cardiac cycle. Recently, a method was developed to measure carotid arterial diameter and intima-media thickness (IMT) from B-m ode images that utilizes computerized edge tracking-multiframe image proces sing that automatically measures arterial diameter and IMT in multiple sequ ential frames spanning several cardiac cycles. To evaluate this method, rep licate B-mode common carotid artery ultrasound examinations and blood press ure measurements were obtained in 24 subjects 1-2 weeks apart. Approximatel y 80 sequential frames spanning two cardiac cycles were analyzed from each ultrasound examination to obtain maximum arterial diameter (D-max), minimum arterial diameter (D-min), and IMT using a computerized edge detection met hod. The intraclass correlations of D-max, D-min, and IMT were 0.97-0.99 an d the mean absolute difference for these measurements were 0.03-0.11 mm. Th e coefficient of variation for D-max and D-min were 1.28 and 1.18%, respect ively. The intraclass correlation for several standard arterial stiffness i ndices, Peterson's elastic modulus, Young's modulus, arterial distensibilit y, compliance, and the beta stiffness index ranged between 0.84 and 0.89. A dditionally, it was determined that averaging IMT over five frames centered at D-min reduced single frame IMT measurement variability by 27% (P = 0.00 5) compared with IMT measured from a single frame corresponding to D-min. C omparison of the phasic relationship of D-max and D-min measured from the B -mode ultrasound image with the simultaneously recorded electrocardiogram ( ECG) signal in the 24 subjects, provided a more accurate method of frame se lection for arterial diameter extrema independent of the ECG signal. The me thod of computerized edge detection-sequential multiframe image processing presented in this paper represents a technological advance for image analys is of B-mode ultrasound images of common carotid arterial dimensions that i s highly reproducible and directly applicable to noninvasive imaging of ath erosclerosis. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.