MDCT angiography of the pulmonary arteries: intravascular contrast enhancement does not depend on iodine concentration when injecting equal amounts of iodine at standardized iodine delivery rates

To compare the impact of iodine concentration using two different contrast materials (CM) at standardized iodine delivery rate (IDR) and overall iodine load in 16-multidetector-row-CT-angiography (MDCTA) of the pulmonary arteries of 192 patients with known or suspected pulmonary embolism. One hundred three patients (group A) received 148 ml of a CM containing 300 mg iodine/ml (Ultravist 300, BayerScheringPharma) at a flow rate of 4.9 ml/s. Eighty-nine patients (group B) received 120 ml of a CM with a concentration of 370 mg iodine/ml (Ultravist 370) at a flow rate of 4.0 ml/s, resulting in a standardized IDR (approximately 1.5 gI/s) and the same overall amount of iodine (44.4 g). Both CM injections were followed by a saline chaser. Mean density values were determined in the pulmonary trunk, the ascending and the descending aorta, respectively. Applying repeated-measures ANOVA, no statistically significant differences between both MDCTA protocols were found (p = 0.5790): the mean density in the pulmonary trunk was 355 +/- 116 Hounsfield Units (group A) and 358 +/- 115 (group B). The corresponding values for the ascending and descending aorta were 295 +/- 79 (group A) and 284 +/- 65 (group B) as well as 272 +/- 71 and 262 +/- 70. In conclusion, the use of standardized IDR and overall iodine load provides comparable intravascular CM density in pulmonary 16-MDCTA for delivering contrast materials with different iodine concentrations.