THE OBJECTIVE CHARACTERIZATION OF ULTRASONIC CAROTID PLAQUE FEATURES

Objective: To determine the influence of ultrasonic carotid plaque mor phology on the incidence of ipsilateral hemispheric symptoms (IHS). De sign: Cross-sectional study. Materials: A consecutive series of 80 pat ients (96 plaques) with more than 50% ICA stenosis was studied. Method s: B mode ultrasonic images were captured and transferred to a compute r of magneto-optic disk and standardised using linear scaling so that adventitia would have a grey scale median (GSM) value of 185-195 and b lood 0-5. The GSM and the percentage of echolucent pixels (PEP) in pla ques were determined to measure echodensity. Homogeneity entropy, and contrast were also determined to measure spatial distribution (heterog eneity) of grey shades in each plaque. Each measurement was cow elated to presence ol absence of IHS. Results: Twenty-five plaques were asso ciated with IHS and 71 plaques were asymptomatic. In symptomatic plaqu es the mean of GSM was 23 and the mean of PEP was 70%, compared to 38 and 55% respectively in asymptomatic plaques (p=0.02; Wilcoxon test). Sixty per cent of symptomatic plaques were associated with a homogenei ty, entropy, and contrast values of >0.2, <2.95, <150 respectively as compared to 40% in asymptomatic plaques. Multiple regression analysis revealed that the GSM and the PEL; were the most significant variables (p = 0.001) that are related to presence or absence of IHS. Conclusio n: This study indicates that computer aided analysis of ultrasonic B m ode features of carotid plaques could identify a potentially high-risk subgroup (patients with IHS). A GSM less than 40 or PEP greater than 50% is a good predictor of IHS related to carotid plaques. The fact th at these measurements are operator independent and performed after ima ge standardisation should encourage their use in multicentre clinical trials where different operators and equipment are used.