Magnetic resonance imaging (MRI) is in general a safe technique, although injuries may occur as a result of failed safety procedures or human error. Though not specifically on MRI exposures or risks, during the last 150 years thousands of papers focusing on the effects or side effects of magnetic or radiofrequency fields, both of which are used in magnetic resonance imaging, have been published. Contraindications or risk-complications to MRI exams may include many active implants, such as cochlear implants and cardiac pacemakers, along with passive objects, including stents, orthopedic implants, as well as shrapnel and metallic foreign bodies. Increasingly, some contraindications are not seen as the absolute prohibitions to MRI scans that they once were, and a skilled provider may be able to find safe ways to make MRI exams accessible to some patients who had previously been prohibited from MRI studies because of an implant, for example, a pacemaker. Since MRI does not use any ionizing radiation, its use generally is favored in preference to CT when either modality could yield similarly valuable information. (In certain cases, MRI is not preferred as it may be more expensive, time-consuming and claustrophobia-exacerbating.)

MRI Safety Regulation International standards regarding the design, manufacture, and marketing of medical devices, including the MRI scanners, themselves, exist and are rather robust. Contemporary reports of MRI accidents and injuries are dominated by point-of-care related events, and not by failure / error / malfunction of MRI scanners. Despite identified, anticipatable, and preventable risks related to point-of-care MRI service, as of 2026 MRI was largely unregulated with respect to minimum MRI safety training, or operational requirements for the protection of patients or healthcare workers in the context of enterprise licenses. Of the few international accreditation organizations that have MRI requirements, they fall well short of the professionally approved model standards or standard of care documents. In short, the decisions of which protections to implement are largely left to the individual MRI providing facility, and are not prescribed by minimum licensure standards.

MRI Safety Personnel Structure and Certification In an effort to standardize the roles and responsibilities of MRI professionals, an international consensus document, written and endorsed by major MRI and medical physics professional societies from around the globe, has been published formally. The document outlines specific responsibilities for the following positions:

MR Medical Director / Research Director (MRMD) – This individual is the supervising physician who has oversight responsibility for the safe use of MRI services. MR Safety Officer (MRSO) – Roughly analogous to a radiation safety officer, the MRSO acts on behalf of, and on the instruction of, the MRMD to execute safety procedures and practices at the point of care. MR Safety Expert (MRSE) – This individual serves in a consulting role to both the MRMD and MRSO, assisting in the investigation of safety questions that may include the need for extrapolation, interpolation, or quantification to approximate the risk of a specific study. The American Board of Magnetic Resonance Safety (ABMRS) has provided testing and board certification for each of the original three positions, MRMD, MRSO, and MRSE, since 2015. In 2026 the ABMRS introduced a fourth certification for MR Safety Tech (MRST), which intends to credential MRI technologist aides in the safety knowledge of a non-technologist needed to manage the environment and patient care. As most MRI accidents and injuries are directly attributable to decisions at the point of care, testing and certification of MRI professionals seeks to reduce the rates of MRI accidents and improve patient safety through the establishment of safety competency levels for MRI professionals.

Implants

All patients are reviewed for contraindications prior to MRI scanning. Many medical devices and implants are categorized as MR Safe, MR Conditional or MR Unsafe (although many medical products or devices remain untested):

MR Safe – The device or implant is completely non-magnetic, non-electrically conductive, and non-RF reactive, eliminating all of the primary potential threats during an MRI procedure. MR Conditional – A device or implant that may contain magnetic, electrically conductive, or RF-reactive components that is safe for operations in proximity to the MRI, provided the conditions for safe operation are defined and observed (such as 'tested safe to 1.5 teslas' or 'safe in magnetic fields below 500 gauss in strength'). MR Unsafe – Objects that are significantly ferromagnetic and pose a clear and direct threat to persons and equipment within the magnet room.

The MRI environment may cause harm in patients with MR Unsafe devices, including some cochlear implants, aneurysm clips, and permanent pacemakers.

Throughout the clinical history of MRI, numerous injuries and fatalities have occurred.

Several deaths have been reported in patients with pacemakers who have undergone MRI scanning without appropriate precautions. Increasingly, MR-conditional pacemakers are available for selected patients, significantly reducing risks of MRI exams for these patients.

Ferromagnetic foreign bodies such as shell fragments, or metallic implants such as surgical prostheses and ferromagnetic aneurysm clips also may also be potential risks. Interaction of the magnetic and radio frequency fields with such objects may produce pulling, twisting, or heating of objects not specifically designed for safety during an MRI. MRI may be contraindicated in those suspected with metallic foreign body in the eye.

Many contemporary implants and medical devices are constructed of materials that minimize the risks in MRI. Titanium and its alloys are one group of metals which are safe from attraction and torque forces produced by the magnetic field

Intrauterine devices with copper are generally safe in MRI, but may become dislodged or even expelled, and it is therefore recommended to check the location of the IUD both before and after MRI.

Other implants that are contraindicated in MRI includes: magnetic dental implants, tissue expander, artificial limb, hearing aid, catheters with metallic components such as Swan-Ganz catheter and piercing. However, tooth amalgam is not contraindicated in MRI.

MRI Risk Categories

Static Magnetic Field Risks of Attraction / Rotation The very high strength of the magnetic field may cause projectile effect (or "missile-effect") accidents, where ferromagnetic objects are attracted towards the magnet. Pennsylvania reported 27 cases of objects becoming projectiles in the MRI environment between 2004 and 2008, though it is widely held that MRI error reporting is under-representative of the actual numbers of incident. There have been incidents of injury and death.Randal C. Archibold, "Hospital Details Failures Leading to M.R.I. Fatality, The New York Times, August 22, 2001Donald G. McNeil Jr, "M.R.I.'s Strong Magnets Cited in Accidents," The New York Times, August 19, 2005. In one case, a six-year-old boy died in July 2001, during an MRI exam at the Westchester Medical Center, New York, after a metal oxygen tank was pulled across the room and crushed the child's head. In a 2025 incident, a man was pulled by a weight-training chain around his neck into an MRI scanner.

To reduce the risk of projectile accidents, magnetic or magnetizable objects and devices are typically prohibited near the MRI scanner and the rooms prior, and patients undergoing MRI examinations must remove all metallic objects, often by changing into a gown or scrubs. Some radiology departments use ferromagnetic detection devices to ensure that no ferromagnetic objects enter the scanner room.

Radio Frequency (RF) Risks of Heating Every MRI scanner has a powerful radio transmitter that generates the electromagnetic field that excites the spins. If the body absorbs the energy, heating occurs. For this reason, the transmitter rate at which energy is absorbed by the body must be limited (see Specific absorption rate). It has been claimed that tattoos made with iron-containing dyes may lead to burns on the subject's body. Cosmetics are very unlikely to undergo heating, as well as body lotions, since the outcome of the reactions between those with the radio waves is unknown. The best option for clothing is 100% cotton.

Risk of implant heating under MRI Electrical currents arising from the radiofrequency field and the switched gradient field may (due to Faraday's law of magnetic induction) produce focal heating (burns). Electrically conductive materials (eg, metals) have at least the potential to heat when exposed to the MRI's electromagnetic fields that are used during imaging.

The amount of heating that takes place has a number of contributing factors:

Injuries have been reported by this heating of metallic implants:

Time-Varying Gradient Risks of Induced Voltages The rapid switching on and off of the magnetic field gradients is capable of causing nerve stimulation. Volunteers report a twitching sensation when exposed to rapidly switched fields, particularly in their extremities. The reason the peripheral nerves are stimulated is that the changing field increases with distance from the center of the gradient coils (which more or less coincides with the center of the magnet). Although PNS was not a problem for the slow, weak gradients used in the early days of MRI, the strong, rapidly switched gradients used in techniques such as EPI, fMRI, diffusion MRI, etc. are capable of inducing PNS. American and European regulatory agencies insist that manufacturers stay below specified dB/dt limits (dB/dt is the change in magnetic field strength per unit time), or else prove that no PNS is induced for any imaging sequence. As a result of dB/dt limitation, commercial MRI systems cannot use the full rated power of their gradient amplifiers.

Acoustic noise Switching of field gradients causes a change in the Lorentz force experienced by the gradient coils, producing minute expansions and contractions of the coil. As the switching typically is in the audible frequency range, the resulting vibration produces loud noises (clicking, banging or beeping). This behaviour, of sound being generated by the vibration of the conducting components, is described as a coupled acousto-magneto-mechanical system, solutions to which provide useful insight to the behaviour of the scanners. This is most marked with high-field machines,"The Evolution of Magnetic Resonance Imaging: 3T MRI in Clinical Applications" , Terry Duggan-Jahns, www.eradimaging.com and rapid-imaging techniques in which sound pressure levels may reach 120 dB(A) (equivalent to a jet engine at take-off), and therefore, appropriate ear protection is essential for anyone inside the MRI scanner room during the examination.The Open University 2007: Understanding Cardiovascular Diseases, course book for the lesson SK121 Understanding cardiovascular diseases, printed by Cambridge University Press, (can be found at OUW), pages 220 and 224.

Radio frequency in itself does not cause audible noises (at least for human beings), since modern systems are using frequencies of 8.5 MHz (0.2 T system) or higher.

MRI-EEG