Magnetic resonance imaging Contrast Media (MRI Contrast Media), also called Magnetic resonance imaging Contrast Agents, which is Gadolinium based contrast agent (GBCA), mainly refers to: after being introduced into the body through a certain way (generally intravenous injection), the MRI contrast media can produce more obvious image contrast between interest range and surrounding tissues. Different from the iodinated Contrast Media of CT/X-ray, the MRI Contrast Media acts indirectly by affecting the proton relaxation time of the molecule. When entering the blood vessels and tissues of the gadolinium-containing Contrast Media in the body, the MRI contrast media products can shorten the relaxation time of T1 to enhance image contrast. The classic Contrast Media for MRI has wide indications, high detection rate, high safety and cost-effectiveness.
Gadolinium Contrast Media possess a very low incidence ( < 2.5 % ) of acute adverse reactions compared to many other drugs. Almost all of their reactions are very mild, the most common are nausea, headache, discomfort at the injection site, vomiting, metallic taste, paresthesia, fever and dizziness.
Immediate hypersensitivity reactions may occur within 1 hour of imaging agents administration, it is approximately 1 in 1000 cases. These are more likely to occur in patients with allergies, asthma, and allergic reactions to gadolinium contrast agents. The most common of these reactions are mild pruritus ( itching ) and urticarial ( hives ). The moderate hypersensitivity reactions occur in about 1 in 5000 cases, it usually includes bronchospasm, facial oedema, arrhythmias, laryngospasm, tachycardia, or widespread urticarial(hives).
The incidence of severe reactions is about 1 in 20,000. A number of severe anaphylactoid reactions to Gd MRI Contrast Media, including death, have been reported worldwide, the risk of death is about 1 in 400,000.
NSF ( Nephrogenic Systemic Fibrosis ) is the most famous of Chronic reactions to Ga Contrast Media. It is a disease of fibrosis of the skin and internal organs, which occurs in patients with chronic severe renal insufficiency. Several hundred patients have been diagnosed worldwide since the first reported case in 2006. NSF has now been largely eliminated as an existing disease with the efforts of the biology community. However, Gd-containing plaques in the extremities have been reported and may represent a forme fruste of NSF.
The US FDA believes that although medical literature reports that there is the deposition of gadolinium-containing Contrast Media in the brain tissue of some patients undergoing 4 or more MRI scans, so far, there are no harmful symptoms, signs, and pathological changes appearing associated with the gadolinium-based contrast agent deposition in brain tissue. In its database of adverse event reporting system, the FDA has received many adverse event reports of patients experiencing pain or other symptoms after single or multiple applications of gadolinium-containing Contrast Media. However, so far, the FDA hasn't been able to clarify common features in these reports. It is not proven yet that the reported symptoms are reasonably related to gadolinium. Further information is needed to evaluate the possible risks caused by gadolinium deposition.
In conclusion, although the incidence of adverse reactions of the gadolinium Contrast Media used in the MRI enhancement examination is very low, one should always keep in mind that any drug administration carries with it the risk of life-threatening reaction, and long-term risks of gadolinium contrast medium deposition must be considered.