Guenther Schneider

We chose to research this topic because there is a great deal of misunderstanding in the literature. The gadolinium (Gd) retention issue has conveniently been classified (by individuals and manufacturing companies) as a macrocyclic versus linear issue. With the memory of nephrogenic systemic fibrosis (NSF) still fresh, it was all too easy to portray all linear gadolinium-based contrast agents (GBCAs) as less stable and “unsafe” and all macrocyclic GBCAs as stable and “safe.” However, NSF occurred primarily with only 3 simple linear GBCAs and not with the substituted linear GBCAs gadobenate or gadoxetate. Moreover, the literature reveals marked differences not only between the general classes of GBCAs (macrocyclic versus linear), but also between GBCAs of the same class. There are now numerous studies that demonstrate T1 signal changes after both linear and macrocyclic GBCAs, but as of yet there is no evidence of any harm or clinical concerns associated with this phenomenon.

Gadobenate is a unique GBCA in that it is both a hepatobiliary agent and a high-relaxivity agent. The latter feature means that lower doses can be given without a loss of diagnostic information compared with other GBCAs at higher doses. We wanted to determine whether T1 signal changes were apparent after multiple administrations of half-dose gadobenate in pediatric patients, as we used this contrast agent because of the lower dose that can be applied. Additionally, unlike the retrospective studies typically reported, we had our images evaluated quantitatively in a blinded fashion by independent readers who were completely unaware of all details related to the cases.

If there is widespread concern about the long-term effects of Gd retention, despite there being no evidence of harm after more than 30 years of GBCA availability (apart from NSF, which was effectively dealt with), then reducing the administered dose, especially for special populations (eg, pediatric patients, patients undergoing routine follow-up or screening, and especially whole-body pediatric imaging), would seem practical. Gadobenate would seem to be the ideal GBCA for this because of its higher relaxivity. Multiple crossover studies across a range of indications demonstrate this. It can be used for both extracellular purposes

(eg, brain imaging, abdomen, soft tissue) and liver-specific imaging, and ideally these different indications can be combined in whole-body imaging with just 1 contrast medium injection at half dose.

Since publication, some authors have criticized the fact that we used only a half dose in our study; however, this is a sufficient dose for imaging due to the higher relaxivity of the agent. Numerous crossover studies have shown that we achieve the same results as with a full dose of a standard-relaxivity agent. We do not see any basis for this criticism; there is no benefit to the patient in using a higher dose than necessary. This is analogous to the ALARA principle in CT.

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