Improving MRI contrast : Contrast agents

Gadolinium chelates

by Denis Hoa

Brand names

  • Dotarem® / Artirem® (Gd-DOTA)
  • Magnevist® (Gd-DTPA)
  • Omniscan® (Gd-DTPA-BMA)
  • Eovist® (Gd-EOB-DTPA)
  • ProHance® (Gd-HP-DO3A)
  • Multihance® (Gd-BOPTA)

Enhancement examples

Pharmacology

Pharmacological and pharmacokinetic data about Gadolinium chelates

 

Toxicity in the free state: Administration in chelate form, of variable chemical structure (linear or macrocyclic) depending on the molecule.

 

Pharmacokinetics similar to that of iodized contrast agents:

  • Biodistribution that is initially intra-vascular with a rapid passage to the interstitial sector
  • Does not pass the healthy blood-brain barrier
  • Elimination by renal route.
  • Gd-BOPTA and Gd-EOB-DTPA: liver-specific properties with excretion in the bile

T2 effect of Gadolinium chelates

 

At weak concentration, the T2 effect of Gadolinium chelates is negligible compared to the T1 effects.
The T2 effect predominates and is only visible at high concentrations, for example in the bladder after renal excretion.
Perfusion MRI also exploits the magnetic susceptibility effect due to the first intravascular passage of a concentrated bolus of Gadolinium chelate, responsible for a drop in the T2 and T2* signal.

 

Intravascular contrast agents

 

New high vascular remanence contrast agents are now available (Gadofosveset Vasovist®). They reversibly bind to the macromolecules present in blood circulation (albumin), which modifies their pharmacokinetics. They remain in blood vessels longer, improving imaging of the vascular system using magnetic resonance angiography.
In research, contrast agents based on Gadolinium chelates bound to macromolecules (polyethylene glycol derivatives) are being studied. Too bulky to pass through the normal endothelium they are able to better characterize cancerous lesions, which are accompanied by increased permeability of the vascular wall.

 

Contraindications and Adverse effects

Contraindications

 

 

  • Allergy
  • Pregnancy (relative contraindication by precautionary principle, to be assessed according to the risk/benefit ratio)

Adverse effects

 

 

  • Nausea, headache, taste alteration, paresthesia
  • Nephrogenic Systemic Fibrosis

Nephrogenic Systemic Fibrosis

 

cutaneous fibrosing impairment with possible visceral extension in the days or months following an injection of Gadolinium chelates, in patients with an inflammatory background, and with severe renal failure and liver transplantation as risk factors.