Kinetic evaluation of an I.V. bolus of MR contrast media

Currently, it is assumed that the pharmacokinetic properties of the first minutes of an I.V. MR contrast media bolus are similar to those of an I.V. iodinated contrast media bolus used in CT. Correct timing of an MRA examination is crucial for obtaining sufficient arterial contrast. This study sought to evaluate the temporal change of arterial signal intensity within 150 s after I.V. bolus injection of Gd-DTPA. Thirty consecutive patients (14 women/16 men; mean age: 51 ± 11 years) were prospectively examined with a 1.0 Tesla clinical scanner. A single axial slice was acquired in 1.25 sec with manufacturer provided gradient echo sequence through the aorta at the level of the renal arteries. Investigation was started simultaneously to the application of contrast media (0.1 mmol/kg bodyweight Gd-DTPA at three different rates 2 mL/sec, 3 mL/sec and 4 mL/sec) and repeated for 2.5 min. An additional echo Doppler examination excluded patients with any cardiac disorders. Maximum signal (1300% increase compared to the basic value) in the aorta was achieved 20 ± 6 sec after start of bolus injection. Then a plateau phase was maintained for the remaining investigation time (2.5 min). No significant difference was shown for different injection rates. After a bolus injection of Gd-DTPA the arterial contrast remains on a high level for at least 2 min. However, correct timing of the bolus arrival is still crucial to discriminate arteries and veins. An injection rate between 2 mL/sec and 4 mL/sec has no influence on early contrast media dynamics.