Gadolinium contrast agents

Molecular complexes containing the rare earth metal gadolinium, chelated to a carrier ligand, form the gadolinium contrast agents (a type of paramagnetic contrast agent) which are the primary class of MRI contrast media. The intravenous route of administration is the commonest.

The gadolinium ion is useful as an MRI contrast agent because it has seven unpaired electrons, which is the greatest number of unpaired electron spins possible for an atom.

Gadolinium molecules shorten the spin-lattice relaxation time (T1) of voxels in which they are present. As a result, on T1-weighted images they have a brighter signal. This can have a number of uses:

Note

  1. IV contrast is not required for all MR angiography, MR venography and MR perfusion sequences
  2. some of the MRI contrast media employ other chemical elements than gadolinium, e.g. iron, manganese

Tissue that demonstrates enhancement following administration of gadolinium-containing IV contrast does so because of a combination of the following two mechanisms 3

  1. intravascular enhancement
  2. interstitial enhancement

Which one of these dominates depends on the characteristics of the tissue. 

Gadolinium shortens T2 relaxation time and actually results in a hypointense signal, indeed at very high concentrations of gadolinium contrast media a signal void may appear to be present.

Most gadolinium contrast agents are excreted through the renal system and therefore have a prolonged half-life in renal failure.

Allergic reactions to gadolinium-based contrast agents are relatively rare, occurring in 0.04-0.3% of administrations, of which 0.4-9% are severe 1-6.

There is an association between the use of gadolinium-based contrast agents in patients with renal failure and nephrogenic systemic fibrosis (NSF). Consequently, gadolinium-based contrast agents are contraindicated for patients who have acute kidney injury or severe chronic kidney disease (such as glomerular filtration rate <30 mL/min) 2.

Gadolinium deposits in trace amounts in various organs, especially the brain (e.g. dentate nucleus of the cerebellum, globus pallidus) following administration of gadolinium-based contrast agents. The clinical significance of gadolinium deposition is heretofore unknown 4.

Macrocyclic agents have less chemical instability than linear agents, resulting in a lower risk of nephrogenic systemic fibrosis and lower gadolinium deposition. On the other hand, cyclic agents have been associated with a higher risk of allergic reactions.

The gadolinium contrast agents can be divided into four groups according to whether the carrier ligand is linear or macrocyclic and whether they are ionic or non-ionic:

Physics and Imaging Technology: MRI
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Article information

rID: 18340
Synonyms or Alternate Spellings:
  • Gadolinium based contrast agent
  • Gadolinium-based contrast agent
  • Gadolinium-based contrast agents
  • Gadolinium-based contrast media
  • Gadolinium-based contrast medium
  • Gadolinium contrast medium
  • Gadolinium contrast media
  • Gad contrast agents
  • Gd contrast agents

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