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MRISAFETY.COM ANNEXURE C Magnetic resonance (MR) imaging has been used to evaluate obstetrical, placental, and fetal abnormalities in pregnant patients for more than 25 years. MR imaging is recognized as a beneficial diagnostic tool and is utilized to assess a wide range of diseases and conditions that affect the pregnant patient as well as the fetus. Initially, there were substantial technical problems with the use of MR imaging primarily due to image degradation from fetal motion. However, several technological improvements, including the development of high-performance gradient systems and rapid pulse sequences, have provided major advances especially useful for imaging pregnant patients. Thus, MR imaging examinations for obstetrical and fetal applications may now be accomplished routinely in the clinical setting. PREGNANCY AND MRI SAFETY The use of diagnostic imaging is often required in pregnant patients. Thus, it is not surprising, that the question of whether or not a patient should undergo an MR examination during pregnancy will often arise. Unfortunately, there have been few studies directed toward determining the relative safety of using MR procedures in pregnant patients. Safety issues include possible bioeffects of the static magnetic field of the MR system, risks associated with exposure to the gradient magnetic fields, the potential adverse effects of radiofrequency (RF) energy, and possible adverse effects related to the combination of these three electromagnetic fields. MR environment-related risks are difficult to assess for pregnant patients due to the number of possible permutations of the various factors that are present in this setting (e.g., differences in field strengths, pulse sequences, exposure times, etc.). This becomes even more complicated since new hardware and software is developed for MR systems on an on-going basis. There have been a number of laboratory and clinical investigations conducted to determine the effects of using MR imaging during pregnancy. Most of the laboratory studies showed no evidence of injury or harm to the fetus, while a few studies reported adverse outcomes for laboratory animals. However, whether or not these findings can be extrapolated to human subjects is debatable. By comparison, there have been relatively few studies performed in pregnant human subjects exposed to MR imaging or the MR environment. Each investigation reported no adverse outcomes for the subjects. For example, Baker et al. reported no demonstrable increase in disease, disability, or hearing loss in 20 children examined in utero using echo-planar MRI for suspected fetal compromise. Myers et al. reported no significant reduction in fetal growth vs. matched controls in 74 volunteer subjects exposed in utero to echo-planar MRI performed at 0.5-Tesla. A survey of reproductive health among 280 pregnant MR healthcare professionals performed by Kanal et al. showed no substantial increase in common adverse reproductive outcomes. There has been on-going concern that acoustic noise associated with MRI may impact the fetus. Reeves et al. (2010) conducted an investigation to establish whether fetal exposure to the operating noise of 1.5-T MR imaging causes cochlear injury and subsequent hearing loss in neonates. The findings in this study provide some evidence that exposure of the fetus to 1.5-T MR imaging during the second and third trimesters is not associated with an increased risk of substantial neonatal hearing impairment. With regard to the publications to date, there are discrepancies with respect to the experimental findings of the effects of electromagnetic fields used for MR procedures and the pertinent safety aspects of pregnancy. These discrepancies may be explained by a variety of factors, including the differences in the scientific methodology used, the type of organism examined, and the variance in exposure duration, as well as the conditions of the exposure to the electromagnetic fields. Additional investigations are warranted before the risks associated with exposure to MR procedures can be absolutely known and properly characterized. MRISAFETY.COM ANNEXURE C GUIDELINES FOR THE USE OF MR PROCEDURES IN PREGNANT PATIENTS As stated in the Policies, Guidelines, and Recommendations for MR Imaging Safety and Patient Management issued by the Safety Committee of the Society for Magnetic Resonance Imaging in 1991, “MR imaging may be used in pregnant women if other nonionizing forms of diagnostic imaging are inadequate or if the examination provides important information that would otherwise require exposure to ionizing radiation (e.g., fluoroscopy, CT, etc.). Pregnant patients should be informed that, to date, there has been no indication that the use of clinical MR imaging during pregnancy has produced deleterious effects.” This policy has been adopted by the American College of Radiology and is considered to be the “standard of care” with respect to the use of MR procedures in pregnant patients. Importantly, this information applies to MR systems operating up to and including 3-Tesla. Thus, MR procedures may be used in pregnant patients to address important clinical problems or to manage potential complications for the patient or fetus. The overall decision to utilize an MR procedure in a pregnant patient involves answering a series of important questions including, the following: -Is sonography satisfactory for diagnosis? -Is the MR procedure appropriate to address the clinical question? -Is obstetrical intervention prior to the MR procedure a possibility? That is, is termination of pregnancy a consideration? Is early delivery a consideration? With regard to the use of MR procedures in pregnant patients, this diagnostic technique should not be withheld for the following cases: -Patients with active brain or spine signs and symptoms requiring imaging. -Patients with cancer requiring imaging. -Patients with chest, abdomen, and pelvic signs and symptoms of active disease when sonography is nondiagnostic. -In specific cases of suspected fetal anomaly or complex fetal disorder. Studies of low-molecular weight water-soluble extracellular substances such as iodinated diagnostic X-ray and computed tomography (CT) and gadolinium-based magnetic resonance imaging (MRI) contrast media in pregnancy have been limited, and their effects on the human embryo or fetus are incompletely understood. Iodinated diagnostic contrast media have been shown to cross the human placenta and enter the fetus in measurable quantities (1, 2). A standard gadolinium-based MRI contrast medium has been shown to cross the placenta in primates and appear within the fetal bladder within 11 minutes after intravenous administration (3). It must be assumed that all iodinated and gadolinium-based contrast media behave in a similar fashion and cross the blood-placental barrier into the fetus. After entering the fetal blood stream, these agents will be excreted via the urine into the amniotic fluid and be subsequently swallowed by the fetus (4). It is then possible that a small amount will be absorbed from the gut of the fetus with the additional swallowed gadolinium-based contrast agents eliminated back into the amniotic fluid. In the study in primates, placental enhancement could be detected up to 2 hours following the intravenous (IV) administration of gadopentetate dimeglumine. When gadopentetate dimeglumine was injected directly into the amniotic cavity, it was still conspicuous at 1 hour after administration (3). There are no data available to assess the rate of clearance of contrast media from the amniotic fluid. MRISAFETY.COM ANNEXURE C Iodinated Low Osmolality Contrast Media Mutagenic effect of LOCM Diagnostic iodinated contrast media have been shown to cross the human placenta and enter the fetus when given in usual clinical doses. In-vivo tests in animals have shown no evidence of either mutagenic or teratogenic effects with low-osmolality contrast media (LOCM). No adequate and well-controlled teratogenic studies of the effects of these media in pregnant women have been performed. Effect of iodinated contrast media on fetal thyroid function The fetal thyroid plays an important role in the development of the central nervous system. There have been rare reports of hypothyroidism developing in the newborn infant after the administration of iodinated contrast medium during pregnancy; however, this occurred only following amniofetography using fat soluble iodinated contrast medium which was performed in the past to detect congenital malformations. Intravenous administration of iodinated contrast medium does not affect short-term neonatal TSH, likely because the overall amount of excess iodide in the fetal circulation is small and transient. However, the long term effects are unknown. To date, there has been no documented case of neonatal hypothyroidis from the maternal intravascular injection of water-soluble iodinated contrast agents (5,6). Given the current available data and routine evaluation of all newborns for congenital hypothyroidism by measurement of thyroid stimulating hormone levels at the time of their birth, no extra attention is felt to be necessary (7, 8, 9). Other adverse effects There have been no other adverse effects that have been reported in the fetus or neonate following administration of LOCM. However, information in this area is sparse. Recommendations prior to performing imaging studies requiring iodinated contrast material administration We recommend that all imaging facilities should have policies and procedures in place to identify pregnant patients prior to the performance of any examination involving administration of iodinated contrast media. If a patient is known to be pregnant, the potential added risks of contrast media should be considered before proceeding with the study (10). There is insufficient evidence to conclude that LOCM are without any risk with respect to the fetus. Consequently, the Committee on Drugs and Contrast Media recommends the following in patients in whom imaging studies are requested that may require the use of iodinated contrast material: A. The radiologist should confer with the referring physician and document in the radiology report or the patient’s medical record the following: 1. That the information requested cannot be acquired without contrast administration. 2. That the information needed affects the care of the patient and fetus during the pregnancy. 3. That the referring physician is of the opinion that it is not prudent to wait to obtain this information until after the patient is no longer pregnant. B. It is recommended that pregnant patients undergoing a diagnostic imaging examination with iodinated contrast media and their referring physicians should indicate that they understand the potential risks and benefits of the procedure to be performed, the potential for risk to the fetus, and the alternative diagnostic options available to them (if any), and that they indicate the desire to proceed. MRISAFETY.COM ANNEXURE C Gadolinium-Based Contrast Agents (GBCAs) Mutagenic effect of GBCAs To date, there have been no known adverse effects to human fetuses reported when clinically recommended dosages of GBCAs have been given to pregnant women. A single cohort study of 26 women exposed to gadolinium chelates during the first trimester of pregnancy showed no evidence of teratogenesis or mutagenesis in their progeny (11). However, no adequate and well-controlled teratogenic studies of the effects of these media in pregnant women have been performed. Risk of nephrogenic systemic fibrosis There are no known cases of NSF linked to the use of GBCAs in pregnant patients to date. However, gadolinium chelates may accumulate in the amniotic fluid. Therefore, there is the potential for dissociation of the toxic free gadolinium ion, conferring a potential risk for the development of nephrogenic systemic fibrosis (NSF) in the child or mother. Because the risk is unknown, it is generally recommended that gadolinium chelates not be used routinely in pregnant patients. Recommendations for the use of GBCA-enhanced MRI examinations in pregnant patients Because it is unclear how GBCAs will affect the fetus, these agents should be administered only with caution. They should only be used if their usage is considered critical and the potential benefits justify the potential risk to the unborn fetus. If a GBCA is to be used in a pregnant patient, one of the agents believed to be at low risk for the development of NSF (12) should be used at the lowest possible dose to achieve diagnostic results. In pregnant patients with severely impaired renal function, the same precautions should be observed as in non-pregnant patients. At the present time, the Committee on Drugs and Contrast Media recommends the following concerning the performance of contrast-enhanced MRI examinations in pregnant patients. Each case should be reviewed carefully and gadolinium-based contrast agent administered only when there is a potential significant benefit to the patient or fetus that outweighs the possible risk of exposure of the fetus to free gadolinium ions. A. The radiologist should confer with the referring physician and document the following in the radiology report or the patient’s medical record: 1. That information requested from the MRI study cannot be acquired without the use of IV contrast or by using other imaging modalities. 2. That the information needed affects the care of the patient and/or fetus during the pregnancy. 3. That the referring physician is of the opinion that it is not prudent to wait to obtain this information until after the patient is no longer pregnant. B. It is recommended that both pregnant patients undergoing an MRI examination and their referring physicians should indicate that they understand the potential risks and benefits of the MRI procedure to be performed, and the alternative diagnostic options available (if any), and that they wish to proceed. PREMEDICATION OF PREGNANT PATIENTS (WITH PRIOR ALLERGIC-LIKE REACTIONS TO IODINATED OR GADOLINIUM-BASED CONTRAST MEDIA Diphenhydramine and corticosteroids (most commonly prednisone and methyl-prednisolone) are commonly used for prophylaxis in patients at risk for allergic-like contrast reactions to contrast media. Diphenhydramine is classified as FDA category B. (FDA category B: Animal reproductive studies have failed to demonstrate a risk to the fetus and there are no adequate well-controlled studies in pregnant women.) Prednisone (FDA category C) and dexamethasone (FDA category C) traverse the placenta; however most of these agents are metabolized within the placenta before reaching the fetus and therefore are not associated with teratogenicity in humans. (FDA category C: Animal reproduction studies have shown an adverse effect on fetus and there are no adequate and well-controlled studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks.) However, sporadic cases of fetal adrenal suppression have been reported. Methylprednisolone also classified as a class C drug, carries a small risk of cleft lip if used before 10 weeks of gestation (16, 17).