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:
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
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.