The other advantage of using lower-dose gadolinium is that multiple doses can be administered. For example, peripheral MRA is imaged at multiple stations. By fractionating the dose, a single dose or less can be used at each station, thereby decreasing the potential amount of gadolinium used overall. This also saves funds. Figure 6 Figure 6 shows an early example of a total thoracic aortogram using a single dose of gadolinium.
Timing is crucial to effective gadolinium-enhanced body MRAs.
Data acquisition must take place when the arteries are enhanced and when the veins are not. Gadolinium chelates are extravascular agents, meaning that they very quickly run from the arteries to the veins before leaching out into the interstitial fluid. Therefore, it is crucial for the data to be collected while there is a maximum difference between the concentration in the arteries and the concentration in the veins. However, if the timing is off and the gadolinium has already shortened the T1 of the blood in the IVC, and possibly even the background, an MIP of these data will produce a mess. One of the noted advantages of MR compared to CTA is that the post-processing time is minimal.