[DECRYPTAGE] MRI & pregnancy: what are the risks associated with electromagnetic fields and Gadolinium?
Julie Kabil, PhD
Anou Sewonu, PhD
Introduction
The risks associated with magnetic and electromagnetic fields1,2 and those associated with contrast media3,4 are now mostly well known and documented. We keep a regular watch on these issues as knowledge advances. In this document, we will deal specifically with the risks associated with MRI examinations during pregnancy, with or without injection of contrast media, based on scientific studies and consensus.
Risks related to magnetic and electromagnetic fields in MRI
Radiofrequency fields can induce overheating, burns and also disruptions to active medical devices2
MRI, the Specific Absorption Rate (SAR) is used to characterize the deposition of power carried by these fields in tissues. Finally, acquisition gradients can generate very intense acoustic noise, as well as Peripheral Nerve Stimulation (PNS). which manifest themselves as involuntary movements, tingling or cramps2.
Risks associated with gadolinium-based contrast media
H and obtain images in T1 weighting with shorter acquisition times. Like all heavy metals, it can be toxic to living organisms. In order to be administered safely, Gadolinium is complexed with with a ligand through the chelation process, forming a Gadolinium-based contrast medium (GBCP). The stability of the Gadolinium-Ligand bond is essential to avoid a release of free Gadolinium into the body. PCBGs are injected intravenously, pass fairly rapidly to the extracellular matrix and should be eliminated relatively quickly by the renal route (≈ 1.5h). In theory, PCBGs do not cross the healthy blood-brain barrier (BBB). With regard to PCBG-related adverse effects, the most notable risk identified is that of nephrogenic systemic fibrosis, a pathology that can affect patients suffering from severe renal failure3,4. Nausea, headache and paresthesia have also been reported. reported4. However, new risks associated with these products have been discovered since the 2010s. In fact, it has been shown that some linear PCBG molecules have less stable Gadolinium-ligand bonds than macrocyclic molecules. Faced with the risk of Gadolinium release presented by linear products, the European Medicines Agency (AME) issued restrictions on their use in 20175.
Furthermore, the presence of Gadolinium has been demonstrated in the brain 6 liver 7 8 and bone 9 from patients with normal kidney function. This raises questions about the risks of toxicity of this heavy metal deposited in these various organs, particularly because of the very long period of time required for its release. natural elimination. Note that these Gadolinium deposits have been demonstrated for both linear and macrocyclic molecules. Research is in full swing on this subject, which could prove thorny and have unexpected consequences for the use of Gadolinium-based contrast agents.
Pregnant women undergoing MRI: examinations without injection of contrast agents
These comparative population studies have shown that exposure to the fields in action in MRI does not appear to be a risk factor. cause particular harm to the fetus. Furthermore, the published results indicate that this This observation applies to all stages of pregnancy 14.
Nevertheless, current clinical practice is to recommend MRI examinations in pregnant women only in situations of absolute necessity, based on a specific risk-benefit analysis. If the examination is necessary during pregnancy, it is still recommended to postpone it beyond the first day of pregnancy. quarter. In addition, the use of MRI equipment with a magnetic field of 1.5T is highly recommended. recommended, as RF power levels are likely to be higher at 3T. For image acquisition, the “Low SAR mode” should be preferred if the pelvic region is located within the explored volume, or the “Normal mode” for any other region. anatomical 11.
Pregnant women undergoing MRI: examinations involving the injection of contrast agents
On the other hand, a retrospective study published in 2016 shows that injection of Gadolinium-based contrast media is strongly correlated with the risk of adverse events such as stillbirths and fetal deaths 14. Learned societies such as the American College of Radiology 16 and the French Society of Neuroradiology (SFNR) 17 strongly advise against injecting Gadolinium-based contrast media into pregnant women. Moreover, in absolute emergency situations, as defined by a risk-benefit analysis, the use of PCBGs should be limited to products with macrocyclic molecules and low doses.
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References
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2: ICNIRP Guidelines for limiting exposure to time-varying electric, magnetic and electromagnetic fields
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5: EMA restrictions on use of linear gadolinium agents in body scans:
https://www.ema.europa.eu/en/medicines/human/referrals/gadolinium-containing-contrast-agents
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