Ultrasonic analysis of plaque characteristics and intimal-medial thickness in radiation-induced atherosclerotic carotid arteries.

OBJECTIVES to investigate the effect of external irradiation on the morphology of atherosclerotic plaques and the intimal-medial thickness of the carotid artery. METHODS a group of 46 patients (16 symptomatic) who had received external irradiation to the head and neck area more than five years previously and developed carotid stenosis exceeding 50%, were evaluated by duplex ultrasound. The carotid artery lumen, intimal-medial complex, and the plaque echogenicity was determined using computer digital image processing methods. Forty-six age and sex matched patients with similar degrees of non-radiation associated carotid stenosis were used as controls. RESULTS irradiated stenotic carotid arteries had a greater intimal-medial thickness (0.96 mm vs 0.80 mm, p=0.008) and a narrower lumen (5.5 mm vs 6.6 mm, p<0.001) than the controls. The carotid plaque characteristics (gray-scale median (GSM) and heterogeneity) of the irradiated and control groups did not differ significantly. Symptomatic patients who had received external radiotherapy to the head and neck have a more echolucent plaque (mean GSM of 98) than their asymptomatic counterparts (mean GSM 114, p=0.03). Intimal-medial thickness and carotid lumen was not related to the occurrence of symptoms. CONCLUSIONS external irradiation to the head and neck area leads to significantly increased thickness of the carotid wall and a corresponding narrowing of the lumen. There seems to be no difference in the plaque characteristics between irradiation-induced and spontaneous carotid atherosclerosis.