COMMON CAROTID INTIMA-MEDIA THICKNESS MEASUREMENT - A METHOD TO IMPROVE ACCURACY AND PRECISION

Background and Purpose High-resolution ultrasonographic imaging is a n onnvasive method that allows estimation of the thickness of the intima -media complex in human carotid arteries. The determination of intima- media thickness involves several steps, each of which may introduce an error that influences the reproducibility of the method. In the prese nt study, apart from the general reproducibility of the determination of intima-media thickness, the error introduced by each step was evalu ated. Methods B-mode scans were performed on 14 randomly selected pati ents. The common carotid arteries were examined in anterior, lateral, and posterior planes, with a standard methodology and by a new method, making use of external reference points. Results The error in general reproducibility in determination of the subject's mean intima-media t hickness was 5.9%. This parameter was also evaluated in a paired manne r after dividing the whole artery into sectors; with this protocol, th e percent error in general reproducibility was 15%. The main source of variability in the evaluation of common carotid intima-media thicknes s was found to lie in the operator's subjectivity in the choice of the carotid sector to be processed (percent error, 10.27%). A method was therefore designed that used external reference points, resulting in r eduction of this error by 38.2%. Conclusions While the mean intima-med ia thickness might be considered a reproducible parameter to evaluate differences between populations exposed to diverse risk factors, evolu tional or therapy-induced changes in the individual may be better moni tored on defined carotid sectors. This may be achieved with a high rep roducibility by use of the proposed method based on external reference points.