The ACR noted, in differing with PRAC recommendations, that “visually observable changes in T1-weighted MR signal do not suggest macrocyclic agents deposit gadolinium within brain tissues,” but it did state that “more quantitative mass spectrometry data from multiple sources have confirmed that they do, albeit at lower levels.”

The ACR also noted that measurement by mass spectrometry has “revealed that gadolinium deposition rates for linear and macrocyclic agents vary within a given class, and that different chemical forms of gadolinium appear to be depositing within tissues, some of which would be undetectable using MR.”


This, they concluded, suggested that while MR signal changes “led to the observation that gadolinium was being deposited in the brain, they are less reliable for determining the quantity of gadolinium deposition in general. This is particularly true for gadolinium species that are not detectable with MR and for lower concentrations of retained gadolinium.”

The ACR concluded that more research was needed to determine the cellular effects and clinical consequences of gadolinium tissue deposition. The group also underscored that these agents have “significant and well-documented diagnostic utility, and in some instances may have more desirable pharmacologic properties or a lower acute reaction risk than macrocyclic agents.”

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