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

Abstract

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.