Three dimensional time-of-flight magnetic resonance angiography in carotid artery surgery: a comparison with digital subtraction angiography.

Three dimensional time-of-flight magnetic resonance angiography (MRA) and intra-arterial digital subtraction angiography (DSA), considered the gold-standard technique, were compared for pre- and postoperative evaluation of the carotid bifurcation. Images of suitable quality of 194 bifurcations were available with both techniques. Percentage stenosis was graded into 5 groups: A = 0-29%, B = 30-59%, C = 60-89%, D = 90-99%, E = 100% (occlusion). Preoperative MRA (126 bifurcations) overgraded the stenosis in 14 cases and undergraded it in 11. The two techniques agreed in 101 cases and the extent of misgrading was never more than one category. Regression analysis showed a good correlation between the two methods. Severe ulceration was better identified by DSA. As far as the surgical indication was concerned, MRA had a sensitivity of 92.6% and a specificity of 98.3%. In 68 operated cases, postoperative MRA and intraoperative completion angiography showed a satisfactory endarterectomy with no residual stenosis in any of the cases. In conclusion, MRA seems an accurate modality for imaging of carotid bifurcations. Significant limitations still exist for an adequate demonstration of intracranial circulation.