Contrast-enhanced magnetic resonance angiography of the carotid arteries: influence of injection rates and volumes on arterial-venous transit time.

Rationale and Objectives: To assess the influence of injection rates and volumes on the arrival time of contrast material (CM) in the common carotid artery, the jugular vein and the resulting arterial-venous transit time. Additionally the relationship between injection parameters and the extent of a CM plateau was evaluated.
Materials and Methods: In 60 patients a CM injection was necessary to investigate suspected cranial disease. All patients were prospectively assigned to 6 protocol groups with varying volumes of gadolinium dimeglumine (2, 10, 20 mL) and injection rates (0.5, 1, 2, 4 mL/s). Simultaneously to the CM injection, 50 repetitive transverse measurements (1/s) were acquired at the level of the common carotid artery. Based on the resulting signal-time curves, the arrival time of the contrast material in the common carotid artery and the jugular vein, the resulting arterial-venous transit time, the peak enhancement and the extent of a CM-plateau were calculated as a function of the injection parameters.
Results: Smaller flow rates (0.5 mL/s) resulted in a longer arrival time in the common carotid artery (mean value 22,6 seconds +/- 2.3) and the jugular vein (mean value 32.6 seconds +/- 2.6) and resulted in longer arterial-venous transit time (mean value 10.1 second +/- 1.9). The volume showed no effect on these parameters. The peak arterial and venous signal intensity and a consistent CM-plateau after 50 seconds were dependent on the volume, but not on the injection rate.
Conclusion: The injection rate showed an influence to the arrival time in the common carotid artery and the jugular vein and also to the arterial-venous transit time. The injected volume only affected the extent of the contrast plateau. A flow rate of 1 to 2 mL/s and a minimum of 20 mL gadolinium dimeglumine are recommended to achieve optimal image quality without venous overlay.