The calcium ratio in carotid plaque, determined by multislice CT, may help risk-stratify patients with asymptomatic stenosis to less aggressive therapy, according to a study by researchers at the University of Virginia Health System.

Risk assessments for stroke have traditionally focused on the degree to which arterial plaque has constricted blood flow, said study team member Dr. Christopher Kramer, a professor of radiology and medicine at Virginia.

"You might say we've been worried about the size of the river channel. This study and others like it indicate we also need to pay attention to the river bank and to the kind of silt that's accumulating there," he said.

CT has been used to study this plaque calcification as a marker of plaque stability in ex vivo and animal studies. Both unstable and stable plaques, however, often contain varying amounts of calcium, and an acceptable in vivo method to define plaques based on this component remains to be developed.

The researchers hypothesized that asymptomatic plaques could be differentiated from symptomatic plaques using MSCT volume measurements of the content of calcified and noncalcified plaque.

Led by Dr. Kiran R. Nandalur, investigators retrospectively reviewed CT angiograms and identified 102 patients with 50% stenosis or more. The study group included 35 symptomatic patients (17 stroke, 13 transient ischemic attack, five amaurosis fugax) and 67 asymptomatic patients (Stroke 2007;38:935-940).

Patient with large calcified plaque involving internal carotid artery. A: Multiplanar reconstructed CT image shows large degree of calcified plaque (arrow) with narrowed lumen (line). B: Multiplanar reconstructed CT image used for volume measurements demonstrates cross-section of internal carotid artery with corresponding lumen (asterisk) and calcified plaque (arrow). (Provided by C. Kramer)