USEFULNESS OF AN INTRAVENOUS CONTRAST-MEDIUM IN THE CHARACTERIZATION OF HIGH-GRADE INTERNAL CAROTID STENOSIS WITH COLOR DOPPLER-ASSISTED DUPLEX IMAGING

Background and Purpose The remaining limitations of ultrasonographic i maging in accurately quantifying internal carotid stenosis or diagnosi ng internal carotid occlusion may be overcome by enhancing the echogen icity of flowing arterial blood with contrast agents. This study asses sed the usefulness of the intravenous (transpulmonary) contrast medium SH U 508 A in improving the characterization and quantification of se vere internal carotid stenosis. Methods We examined 32 patients (30 ha d vessels with a stenosis of greater than 70% luminal narrowing and 2 had vessel occlusions) using a 7.5-MHz linear-array transducer for col or Doppler-assisted duplex imaging before and after injection of the c ontrast medium. Results The SH U 508 A-induced increase in carotid blo od echogenicity began 11+/-2 (mean+/-SD) seconds after the start of th e bolus injection, peaked at 21+/-2 dB, and showed a half-life of 75 s econds. Quantitative vascular measurements (cross-sectional luminal ar ea reduction and plaque length, respectively) obtained before and afte r contrast application were highly correlated (r>.90). Visualization o f the entire length of the intrastenotic residual flow lumen, however, was significantly improved by contrast enhancement (52% versus 83%, P =.01). Conclusions This pilot study on patients with extracranial caro tid artery disease suggested that ultrasonic contrast media may be mos t useful in improving the ultrasonography-based diagnosis of internal carotid occlusion.