CT pulmonary angiography using a reduced volume of high-concentration iodinated contrast medium and multiphasic injection to achieve dose reduction.

Aim: To evaluate whether a reduced volume of a higher-concentration iodinated contrast medium delivered with a multiphasic injection could be used in computed tomography pulmonary angiography (CTPA) to achieve a reduction in dose without adversely affecting image quality.

Materials And Methods: The CTPA images were retrospectively evaluated of 69 patients who received 100 ml of 300 mg iodine/ml ioversol, injected at constant rate of 5 ml/s and 70 patients who received 75 ml of 350 mg iodine/ml ioversol contrast medium delivered using a multiphasic injection protocol (starting at 5 ml/s and reducing exponentially). The degree of opacification in the proximal pulmonary arteries was measured in Hounsfield units.

Results: The groups did not differ in terms of age, sex distribution, or weight. The mean iodine dose was lower in the 75 ml of 350 mg iodine/ml group (26.25 versus 29.5 g, p < 0.0001). Mean opacification did not differ significantly between the 75 ml of 350 mg iodine/ml and 100 ml of 300 mg iodine/ml groups in the main pulmonary artery (365 versus 331, p = 0.055) although it was significantly higher in the 75 ml group in the right (352 versus 315, p = 0.024) and left pulmonary arteries (347 versus 312, p = 0.028). Opacification correlated positively with age and negatively with weight (p < 0.001) and when these effects had been accounted for, the differences in opacification were not statistically significant in the main (p = 0.23), right (p = 0.11), or left pulmonary arteries (p = 0.13). The number of suboptimally opacified studies (opacification of less than 250 HU in main pulmonary artery) did not differ between the groups (12 versus 13, p = 0.83).

Conclusion: A reduction in iodine dose can be achieved without adversely affecting pulmonary arterial enhancement in CTPA by administering a smaller volume of high-concentration contrast medium using a multiphasic injection protocol.