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.