Sixteen-detector row CT angiography of carotid arteries: comparison of different volumes of contrast material with and without a bolus chaser.

PURPOSE: To prospectively compare different volumes of intravenously administered contrast material with and without a bolus chaser at 16-detector row computed tomographic (CT) angiography of the carotid arteries.
MATERIALS AND METHODS: Institutional Review Board approval and informed consent were obtained. Seventy-five consecutive patients (44 men, 31 women; mean age, 63 years; range, 22-85 years) were allocated to one of three protocols: group 1, 80 mL of contrast material; group 2, 80 mL of contrast material followed by 40 mL of saline; and group 3, 60 mL of contrast material followed by 40 mL of saline. Bolus tracking was used to synchronize contrast material injection with CT scanning. The attenuation in Hounsfield units was measured from the ascending aorta to the intracranial arteries at 1-second intervals. Differences were tested with the Student t test.
RESULTS: The maximum attenuation was reached in the proximal internal carotid artery in all groups. The addition of a bolus chaser to 80-mL contrast material resulted in a higher mean attenuation (323 HU +/- 39 vs 351 HU +/- 60, P = .06), higher maximum attenuation (393 HU +/- 53 vs 425 HU +/- 76, P = .09), and higher minimum attenuation (240 HU +/- 34 vs 264 HU +/- 48, P < .05). Group 3 had lower mean, maximum, and minimum attenuation than did groups 1 and 2 (P < .001).
CONCLUSION: The addition of a bolus chaser to 80 mL of contrast material results in a slightly higher attenuation. Decreasing the volume of contrast material from 80 to 60 mL results in a significantly lower attenuation.