During the examination, the patient moved his leg for comfort and inadvertently pinned the radiofrequency coil cable between his bare calf and the magnet bore. After training and safety screening are performed, level 1 personnel can have unrestricted access to zones III and IV on an annual basis. If a patch is kept on the patient, special care must be taken to ensure that the patch is not too close to a coil, a cable, or the magnet bore. SAR estimation requires knowledge of the electric field at each point inside the patient’s body, along with knowledge of local tissue conductivity, both of which are variable (22). For example, Publication F2182 details the method for measuring radiofrequency-induced heating of devices. 0 17, No. For this reason, the entry doors to an MR imaging suite are bulkier than conventional doors and contain specialized handles that form a conductive seal around the entire frame when turned to the closed position. 826 75 0000002576 00000 n (a) Photograph shows a third-degree burn on a patient’s calf, which was pressed against the cable of the radiofrequency coil. It is especially critical that all potential emergency responders are aware of the hazards associated with zone IV, as it is easy to forget to properly screen for potential ferromagnetic projectiles during an emergency response. However, other devices require more caution. Many of these devices are composed of nonferromagnetic materials that do not pose a risk of force-related injury. Level 2 personnel must undergo safety screening, as level 1 personnel do. These roles include MR Medical Director (MRMD), MR Safety Officer (MRSO) and MR Safety Expert (MRSE) An accredited center must have a documented MR imaging safety policy tailored for its practice that is reviewed annually by a supervising MR imaging physician, covering everything from signage and access control to patient screening and mechanical safety. The FDA sets a maximum of 140 dB for an MR imaging system and a maximum of 99 dB for a patient with hearing protection (35). 0000015749 00000 n The ACR states that level 1 personnel can move within zones III and IV freely. startxref (a) Photograph shows a third-degree burn on a patient’s calf, which was pressed against the cable of the radiofrequency coil. The use of gadolinium-based contrast agents (GBCAs) in MR imaging is well established. If a patient is older than 60 years of age or has any positive answers on the questionnaire, eGFR is calculated by using the Modification of Diet in Renal Disease (MDRD) equation and a serum creatinine level obtained within 30 days of the MR imaging examination. More common are burns from electromagnetic induction, where generated current from changing magnetic fields produces an excessive amount of heat, analogous to an excessive local SAR. Each MR imaging site must also have a diagnostic medical physicist or MR imaging scientist to evaluate the performance of the MR imaging unit and receiver coils and to document that each unit meets the requirements for imaging performance set by the Joint Commission, the ACR, or other regulatory body. (b) Photograph shows a phased-array coil similar to the one involved in the incident. It is prudent to screen all girls and women of reproductive age for pregnancy before granting them access to the MR imaging environment. 0000009489 00000 n U.S. MR imaging centers are subject to quality and safety standards through two major mechanisms: requirements set by the U.S. FDA, which govern patient exposure limits and contrast agent regulation, and agency accreditations from the American College of Radiology (ACR) and the Joint Commission, which are now required for Medicare reimbursement. Severe anaphylactoid reactions, while extremely rare, do occur, and the ACR recommends that patients with previous reactions be injected with a different contrast agent if one is needed for subsequent MR imaging and that at-risk patients be premedicated with corticosteroids and antihistamines. Basic knowledge of MR imaging physics and hardware is necessary for radiologists to understand the origin of safety regulations and to avoid common misconceptions that could compromise safety. Translational and rotational forces can result when any metallic object interacts with static or changing magnetic fields. The strong main magnetic field of MR imaging units and the fact that the magnetic field is always on creates important safety issues in and near the MR imaging environment. Magnetic resonance (MR) imaging, introduced in the 1970s, is now commonplace in modern medicine, with more than 60 million examinations performed worldwide in 2012 (1). 0000137828 00000 n Policies from the authors’ own practice are provided for additional reference. 0000004792 00000 n 0000010704 00000 n Figure 1. In addition to a known history of renal insufficiency, other risk factors outlined by the ACR include a history of diabetes or hypertension requiring therapy, age older than 60 years, and prior renal surgery or malignancies (40). 0000003619 00000 n Send your completed document as an email attachment to the MRI Safety officer : Although no adverse effects to the fetus or neonate have been established, intravenously administered GBCAs are known to enter fetal circulation and to persist within the amniotic fluid. In one case, a gun that was unintentionally brought into the imaging suite was pulled into the bore, discharging a round despite having its safety engaged (20). 10, No. Transient discomfort and first-degree burns have rarely occurred with permanent eyeliners, which do not necessarily contain ferrous materials (28,29). Increasing overlap and matching of the safety requirements set by the Joint Commission, the ACR, and the FDA have helped to create a more cohesive set of safety requirements. SAR limits have also been declared for MR-conditional devices, specifically to reduce the risk of thermal injury. For example, unintentional resonances of this kind can occur if a coiled cardiac pacer lead forms a resonant configuration; however, in many cases, the cause is far less obvious. Temporary hearing loss has been documented in patients who underwent routine MR imaging examinations without protective devices (37). For example, some transdermal medicinal patches containing trace aluminum have caused superficial burns (24). Newer-generation systems reduce noise levels by use of additional passive noise shields and active techniques such as noise-minimizing “silent” or “quiet” pulse sequences (38). The screening form may be completed by the patient’s health care proxy and be confirmed with one of the patient’s health care providers (physician, physician assistant, or nurse practitioner), who can also review the medical records. However, long-term safety has not yet been definitively demonstrated, and there is lack of consensus as to whether risks to the fetus, including possible teratogenic effects and acoustic damage, are real (58). MR Safety Reference Documents. Thus, the restricted area may extend not only in all directions on the same floor of the facility but also potentially through the floor and/or ceiling to adjacent floors. Gradient or radiofrequency coils provide the source of the fluctuating magnetic fields, but the current can be produced within any conducting material, either internal or external to the body. These rapid fluctuations in current result in microscopic movements of the coils, which lie within an audible frequency range; this is the source of the knocking and buzzing noises generated by an MR imaging unit during an examination. As discussed previously, the main magnetic field is left on constantly, and a proper shutdown requires down-ramping of the current in a slow and controlled manner. Recently, U.S. and Canadian multidisciplinary society guidelines were issued to better guide appropriate use of MR imaging in patients with cardiac implants (14,34). They require dedicated cooling systems to counteract the heat induced by the large and changing currents. The ACR Manual on MR Safety addresses numerous MR safety-related topics such as: A detailed discussion of the hazards of the multitude of medical devices is beyond the scope of this article; only a few illustrative examples are used in the following sections. Nearly all cases have been observed in patients with stage 4 chronic kidney disease (eGFR, 15–29 mL/min/1.73 m2), stage 5 chronic kidney disease (eGFR <15 mL/min/1.73 m2), or acute kidney insufficiency (43–45,48,49). Online supplemental material is available for this article. A magnet quench can also occur spontaneously, secondary to faulty equipment, power failure, or inadequate liquid helium levels. 0000008885 00000 n 0000007360 00000 n Deaths can occur owing to respiratory failure and limited mobility (41–43). 0000165381 00000 n The ACR Committee on Drugs and Contrast Media considers a patient at risk for developing NSF in the following conditions (40): (a) undergoing dialysis; (b) chronic kidney disease stage 4 or 5 (eGFR <30 mL/min/1.73 m2) without dialysis; (c)eGFR of 30–40 mL/min/1.73 m2, without dialysis, due to potential short-term fluctuations in eGFR that may result in a level below 30 mL/min/1.73 m2; or (d) acute kidney insufficiency. 0000016606 00000 n Retained wires that are short and have no potential to form loops may be safe for MR imaging. To achieve such currents in a conventional electromagnet would require a massive amount of continuous power. The majority of MR imaging unit noise originates from gradient coils because they are subject to rapid changes in current, which in turn interact with the main magnetic field through Lorentz forces. This video will drive home a simple message: the MRI machine is ALWAYS on. These guidelines were developed on the basis of established knowledge of electromagnetism as well as experience from adverse events. These safety zones were introduced by the American College of Radiology (ACR) [7]. 0000003968 00000 n Zone I and the strictly controlled Zones III and IV. For example, while this article was being drafted, the ACR Subcommittee on MR Safety issued a new standardization request detailing several aspects of device safety reporting, including how maximum magnetic gradient strength should be documented, and clarifying reports on torque deflection angle and radiofrequency transmission power (8). MR imaging studies that pose the greatest risk of peripheral neurostimulation are those that involve high-bandwidth readouts and/or rapid gradient switching, such as echo-planar imaging. Personnel should have an annual refresher in MR Safety. For patients with a decrease in eGFR of more than10 mL/min/1.73 m2 or for patients in whom there is a desire to give a GBCA for a subsequent MR imaging examination in a time period less than that recommended, we discuss the case with the referring clinician to decide on the best course of action. Every magnet room is encased by a thin metallic shield to block all external electromagnetic signals that might fall within the operating frequency. Newer magnets, such as this 1.5-T unit, use active shielding to bring the 5-G line as close as possible to the bore. 0000007228 00000 n Don't believe it? The Joint Commission recommends that MR imaging technologists participate in continuing education, which includes annual training on safe MR imaging practices in the MR imaging environment (63). 0000135076 00000 n An action plan that lays out personnel responsibilities in the event of a quench should also be in place. In the event of a shift change or lunch break, no level 2 personnel shall relinquish their responsibility to supervise non–MR imaging personnel while still in zone III or IV until such supervision has been formally transferred to another of the site’s level 2 personnel. Reducing the read bandwidth or increasing the repetition time can reduce dB/dt. labeled zones—with progressive restriction of entry and increased supervision for higher zones—is a mandatory and key aspect in avoidance of MR imaging–related accidents. The FDA is best known for approval and regulation of medications, which include intravenous contrast agents for MR imaging. The 5-G line is marked in yellow for each magnet. Pens, bobby pins, hairclips, etc. Zone I is freely accessible to the general public. However, abandoned intracardiac pacer wire leads lack such protection and are currently considered a contraindication to MR imaging. The Joint Commission and/or the ACR require each institution to have written policies covering all of these topics. Radiologists and trainees who rarely enter the environment (eg, nuclear medicine physicians and trainees or interventional radiologists who may never enter zones III and IV) could be level 1 personnel, which would allow them to enter the MR imaging environment in an emergency. Tattoos are known to cause susceptibility artifacts, but thermal injuries rarely happen and are suspected to occur only with very dark inks, which are richer in iron oxide, or if the inking pattern forms a loop (27). 826 0 obj <> endobj Thus, if a medical emergency or fire occurs within zone IV, any ongoing imaging examination should be terminated, and every effort should be made to move the patient and all personnel outside zone IV while preliminary resuscitation or stabilization is begun by appropriately trained and certified MR imaging personnel. MRI BIOEFFECTS, SAFETY, AND PATIENT MANAGEMENT is a comprehensive, authoritative textbook on the health and safety concerns of MRI technology that contains contributions from more than forty internationally respected experts in the field. Room ( zone 4 is defined as the distance to the general public however also... The one involved in the incident the superconducting threshold and ceases to superconducting... 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