Patient safety issues in magnetic resonance imaging: state of the art

Abstract

The presence of a static magnetic field (Bo), a radiofrequency field (RF), a dynamic gradient which varies in time and loud noises during an MR examination could increase patient risk. Specifically, a magnetic field could interfere with ferromagnetic material leading to one of the following five dangerous interactions: 1) projectile effect, 2) twisting, 3) burning, 4) artefacts and 5) device malfunction. The projectile effect is when an object is attracted by the magnet with the risk, as reported in literature, of hitting the patient, operators and/or the instrument. Objects which typically can undergo this effect are oxygen and helium cylinders, IV stands, cleaning trolleys, chairs, lamp holders, scissors, forceps, clampers, traction weights, monitoring instruments, and especially metallic splinters within the patient. Twisting (torsion) typically occurs with cerebral vascular clamps and cochlear implants. If parts of implants are involved a malfunction may result. Burns can be caused when electrically conductive material is introduced within the magnet, for example, ECG electrodes, monitoring cables and coils which are in contact with the patient's skin, as well as tattoos and eye-liners that contain iron-oxides. Artefacts can be induced by RF emission of implanted devices which can be mistaken for noise of the receiving coil. Implanted devices can induce signal voids which mask or simulate pathologies. Electrical or mechanical malfunction of implanted devices includes pacemakers which can stimulate inappropriately or at an elevated frequency yielding a distorted ECG with altered T-waves. The risk for patients can be reduced by specific educational programs within individual radiology departments which include other specializations and external referring physicians with the aim of developing a standardized safety protocol.

Radiofrequency-induced Heating near Fixed Orthodontic Appliances in High Field MRI Systems at 3.0 Tesla

“…While MRI is generally considered a safe diagnostic procedure, most incidents have occurred in patients with metallic implants [4,22]. Excessive radiofrequency-induced heating can be a concern.…”

Keeping Patients Safe During Intrahospital Transport

“…The magnetic field of the equipment used for magnetic resonance imaging reacts to the detection of metal in 5 dangerous ways: projectile objects, twisting displacement of implants, burning, monitoring artifacts, and device malfunction. 62,63 Medical devices currently contraindicated for magnetic resonance imaging include pulmonary artery catheters, implantable cardioverter defibrillators, pacemakers, ventricular assist devices, and intraaortic balloon pumps. 63 Technology is constantly changing with respect to medical devices and safety of magnetic resonance imaging.…”

Fetal magnetic resonance imaging and ultrasound

“…With the conventional 1.5-and 3-Tesla machine, no clinically significant fetal effects have been reported [11]. The MRI should be avoided in the first half of pregnancy, particularly at < 18 menstrual weeks'.…”