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[DECRYPTAGE] MRI & pregnancy: what are the risks associated with electromagnetic fields and Gadolinium?

Julie Kabil, PhD
Anou Sewonu, PhD

Introduction

Magnetic Resonance Imaging (MRI) is the modality of choice for the study of many pathologies, as it can produce very high quality images without exposure to ionizing radiation. However, this imaging technique is not without its risks. non-ionizing radiation and its effects, the phenomenon of the projectile effect causing accidents, and exposure to contrast media.

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

A brief reminder of the fields and risks involved in MRI: to generate images, the machine MRI emits an intense and permanent static magnetic field, electromagnetic fields of and gradient-switched fields (also known as acquisition gradients). On the one hand, the static magnetic field can lead to accidents due to the projectile effect (if an object ferromagnet is brought into the MRI room), malfunctions of implanted medical devices such as pacemakers, but also benign and transient phenomena such as sensations of ^dizziness1.
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

Gadolinium is a heavy metal chemical element. Thanks to its paramagnetic properties, it can be used to modify the proton relaxivity¹.
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

When pregnant women undergo MRI examinations, they may be affected by the different MRI fields. While the influence of the static magnetic field is very difficult to assess The scientific literature is full of studies on the risks of heating and noise. for the fetus. In 2006, work based on numerical modeling showed that localized SAR levels in the fetus can reach 40-70% of the maximum SAR measured in the mother ¹⁰. As for acoustic noise, maternal tissue and amniotic fluid help to attenuate sound levels. High frequencies are much better attenuated than low frequencies, which can even be amplified. The risk of hearing loss is therefore theoretically possible 11. However, various retrospective studies have shown no difference between fetuses whose mothers were exposed to MRI and those whose mothers were not, in terms of auditory risks 12,13 and risks of congenital anomalies and fetal death ^13,14.
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

The injection of Gadolinium-based contrast media is strongly discouraged for pregnant patients. Passage of the placental barrier has been demonstrated in primates, with traces of contrast medium remaining in the fetal kidneys for up to 45 hours after injection 15.
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.

Spin Up advises and supports you

In conclusion, if it is necessary for the patient and the examination cannot be postponed, MRI imaging can be carried out in pregnant women on the basis of a risk/benefit analysis and by maintaining operating levels in “low SAR” or normal mode. The use of Gadolinium-based contrast media is strongly discouraged in these patients, except in the following cases absolute emergency. In such situations, the contrast medium must be a macrocyclic molecule and administered in very low doses. SPIN UP puts at your service a team of MRI physicists to advise you, train your teams and support you in the safe management of your pregnant patients.

References

1: ICNIRP Guidelines on limits of exposure to static magnetic fields. Health Physics Society. 2010
2: ICNIRP Guidelines for limiting exposure to time-varying electric, magnetic and electromagnetic fields
(up to 300 GHz). Health Physics Society. 2010
3: Fraum T J et al. Gadolinium-based contrast agents: A comprehensive risk assessment. Journal of
Magnetic Resonance Imaging. 2017
4: Fox-Rawlings S, Zuckerman D. The Health risks of Gadolinium-based contrast agents used in MRIs.
National Center for Health Research. 2019
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
6: Kanda T et al. High signal intensity in the dentate nucleus and globus pallidus on unenhanced T1-
weighted MR images. Radiology. 2014
7: Maximova N et al. Hepatic Gadolinium deposition and reversibility after contrast agent-enhanced
MR imaging of pediatric hematopoietic stem cell transplant recipients. Radiology.
8: Roberts D R et al. High levels of Gadolinium deposition in the skin of a patient with normal renal
function. Investigative Radiology. 2016
9: Murata N et al. Macrocyclic and other non-group 1 Gadolinium contrast agents deposit low levels
of gadolinium in brain and bone tissue. Preliminary results from 9 patients with normal renal function.
Investigative Radiology. 2016
10: Hand J W et al. Prediction of Specific Absorption Rate in mother and fetus associated with MRI
examination during pregnancy. Magnetic Resonance in Medicine. 2006
11: Lum M and Tsiouris A J. MRI safety considerations during pregnancy. Clinical Imaging. 2020
12: Chartier A L et al. The safety of Maternal and fetal MRI at 3T. AJR. 2019
13: Strizek B et al. Safety of MR imaging at 1.5T in fetuses: A retrospective case-control study of birth
weights and the effects of acoustic noise. Radiology. 2015
14: Ray J G et al. Association between MRI exposure during pregnancy and fetal and childhood
outcomes. JAMA. 2016
15: Oh K Y et al. Gadolinium chelate contrast material in pregnancy: Fetal biodistribution in the
nonhuman primate. Radiology. 2015
16: ACR-SPR PRACTICE PARAMETER FOR THE SAFE AND OPTIMAL PERFORMANCE OF FETAL MAGNETIC
RESONANCE IMAGING (MRI). 2020
17: Lersy F et al. Consensus Guidelines of the french Society of Neuroradiology (SFNR) on the use of
Gadolinium-Based Contrast Agents (GBCAs) and related MRI protocols in Neuroradiology. Journal of
Neuroradiology. 2020

[DECRYPTAGE] MRI & pregnancy: what are the risks associated with electromagnetic fields and Gadolinium?

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