Computer analysis of ultrasonic plaque echolucency in identifying high risk carotid bifurcation lesions

Objectives: to confirm that plaque echogenicity evaluated by computer analysis, as suggested by preliminary studies, can identify plaques associated with a high incidence of strokes. Materials and methods: a series of 96 patients with carotid stenosis in the range of 50-99% were studied retrospectively (41 with TIAs and 55 asymptomatic). Carotid plaque echogenicity was evaluated using a computerised measurement of the median grey scale value (GSM). All patients had a CT brain scan to determine the presence of infarction in the carotid territory. Results: the incidence of ipsilateral brain CT infarctions was 16% in the asymptomatic and 32% in the symptomatic plaques (p = 0.076). It was 20% for < 70% stenosis and 25% for > 70% stenosis (p = 0.52). It was 9% for plaques which had a GSM > 50 and 40% in those with GSM < 50 (p < 0.001) with a relative risk of 4.6 (95% CI 1.8 to 11.6). Conclusions: the results confirm that computer analysis of plaque echogenicity is better than the degree of stenosis in identifying plaques associated with an increased incidence of CT brain-scan infarction and consequently useful for identifying individuals at high risk of stroke. What is required is a form of image standardisation in order to apply this method to natural history studies with stroke as the endpoint.