![]() Approximately 1,000 liters of liquid helium resides in a cryostat, which is essentially a thermos bottle inside the MRI. Most contemporary high-field (1 Tesla or higher) clinical MRI systems rely on liquid helium that is more than 450 degrees Fahrenheit below zero. The magnet grabbed the steel cylinder and drew it into the bore, where it crashed into the boy, killing him. This accident occurred when an oxygen cylinder was brought into the MRI scan room while the young boy was inside the bore of the magnet. In fact, 2006 marks the 5-year anniversary of the most infamous missile effect fatality, that of a 6-year-old post-operative patient receiving a follow-up scan at Westchester Medical Center in New York. The attractive force exerted by MRI magnets on ferromagnetic objects has frequently and repeatedly resulted in accidents jeopardizing the safety of patients and staff, as well as the MRI equipment itself (See figure 1). Iron-containing materials, including steel, can be drawn to an MRI with such force that they become airborne, accelerating at speeds of up to 40 miles per hour. Images provided courtesy of Īlso referred to as the projectile effect, the missile effect is the tendency of the extreme strength of contemporary MRI magnets to draw ferromagnetic materials into the center of the magnet. This single codified standard, by virtue of its inclusion in MRI vendor siting documents, is the only standard of facility safety incorporated in the planning and design of many MRI facilities.Īn example of the missile or projectile effect of MRI magnets on items containing ferromagnetic materials. However, either because of the strength of the magnet or the simple three-dimensionality of the magnetic field, 5-gauss threats can penetrate the magnet room enclosure and present themselves in adjacent areas, including above and below. In essence, access to this portion of the three-dimensional bubble of magnetic force is to be limited to only those persons who have successfully cleared screening for contraindicated devices.įortunately, many contemporary magnet systems have so effectively compressed the reach of the stray magnetic field through active shielding technologies that, in many suites, the 5-gauss line can be completely enclosed within the magnet room. In response to this risk, MRI equipment manufacturers and government regulators recognize the 5-gauss exclusion zone. ![]() Devices as varied as pacemakers, cochlear implants, implanted insulin pumps, and Vagus nerve stimulators all can be impaired or incapacitated, resulting in significant injury or even death. While magnetism doesn't pose a biological hazard to people, magnetic fields can disrupt implanted (or on-planted) medical devices. Facility safety, by contrast, has long been the "weak link" in an effective program for reducing accidents and facility liability. Clinical and operational components of MRI safety have been the subject of significant inquiry and many published papers. Neglecting any one constituent part jeopardizes the efficacy of MRI safety initiatives. Like a tripod, MRI safety is comprised of three integral components: clinical safety, operational safety, and facility safety. Provided courtesy of the American College of Radiology. Each accident and close call puts patients and staff at risk and carries the potential of damaging, if not crippling, over a million dollars worth of imaging equipment.Ĥ-Zone diagram reproduced from the American College of Radiology's White Paper on MR Safety, combined papers of 20. The proliferation of MRI equipment and significant increases in both magnet strength and spatial gradients (the rate at which magnetic field strength increases as you approach its center) have increased the number of accidents occurring in the MRI suite. While exposure to magnetic energies has shown no harmful biological effects unlike modalities that rely on ionizing radiation such as CT or conventional X-ray there are still many accidents and incidents that jeopardize the safety of patients and staff in the MRI suite. ![]() Today's high-strength clinical MRI scanners are up to 60,000 times the strength of the Earth's own ambient magnetic field. MRI suites hold unique dangers for patients and staff.
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