Hypoechoic plaque at US of the carotid artery: an independent risk factor for incedent stroke in adults aged 65 years or older. Cardiovascular Health Study. - Polak,J.F.; Shemnski,I.; O'Leary,D.H.; Lefkowitz,D.; Price,T.R.; Savage,P.J.; Brant,W.E.; Reid,C. (Radiology, 1998)