Comparison of 40 and 60 Milliliters of Contrast in Assessment of the Carotid Artery by Computed Tomography Angiography

Background: Although fast acquisition of multidetector-row computed tomography (MDCT) can make it possible to acquire sufficient early vascular enhancement using small volumes and high concentrations of contrast material (CM), there are still some problems with nephrotoxicity and costs related to CM. Purpose: To compare the qualitative and quantitative performance in cervicocranial CT angiography (CTA) using two different iodine volumes and concentrations of CM. Material and Methods: CTA ranging from the aortic arch (AA) to distal to the circle of Willis (cW) was performed on a 32-MDCT system. Fifty-eight patients were randomly divided into two groups: group A (29 patients) received 60 ml of 300 mg I/ml CM, and group B (the other 29 patients) received 40 ml of 370 mg I/ml CM. Time to peak arterial enhancement at cW (Tc) was calculated. As scan speed was 96.9 mm/s and injection rate was 4.0 ml/s, scanning delay was individually decided according to Tc and scan duration between AA and cW. Arterial attenuation along the z-axis at eight points in the carotid-cerebral artery and venous attenuation of the internal jugular vein (IJV) at carotid bifurcation were measured. Mean attenuation values were then quantitatively analyzed. Postprocessing images were qualitatively assessed. Results: Arterial attenuation profiles revealed maximum attenuation at the distal common carotid artery in both groups. Although there were no significant differences in mean arterial attenuation in group A versus group B (402±70 HU vs. 407±67 HU; P=0.78), venous attenuation of the IJV was lower in group B than in group A (114±57 HU vs. 224±81 HU; P<0.001). Although arterial images demonstrated no difference qualitatively between the two groups, the venous contamination of IVC was less prominent in group B. Conclusion: Although a different amount of CM was administered in both groups, quantitative and qualitative arterial images did not show significant differences between the two groups