Carotid arteriography

Contrast-enhanced MR angiography (CEMRA) is the latest in a long line of noninvasive techniques developed to provide images of the carotid arteries. All of these techniques only indirectly determine the status of the carotid artery by studying the blood that flows through it. Doppler ultrasound measures the velocity of red blood cells and uses the magnitude of the velocity increase to infer the degree of vessel narrowing. Time of flight MR angiography takes advantage of the effect of motion on the proton MR signal to define the limits of the column of flowing blood. CT angiography and CEMRA rely on the IV injection of substances that change the signal characteristics of blood so that it shows up in high contrast relative to other structures. Digital subtraction arteriography (DSA) employs transfemoral introduction of small flexible catheters into the carotid artery with direct intra-arterial injection of radiographic dye and digital image enhancement. Even in the best of hands, DSA still carries a procedural risk of 1 to 4% for stroke and death.1,2⇓ Why, then, is DSA still widely considered the gold standard for evaluation of the carotid arteries when the other noninvasive techniques carry a much lower risk? The answer lies in the randomized, controlled, clinical trials that demonstrated the superiority of endarterectomy over medical therapy alone for the prevention of subsequent stroke in symptomatic patients. These studies showed that the degree of carotid stenosis was the most …