Which risk is associated with time-varying magnetic fields in MRI?

Time-varying magnetic fields in MRI can induce electric currents within conductive materials in their vicinity. This phenomenon occurs due to electromagnetic induction, where a changing magnetic field generates an electric field, resulting in currents that can flow through nearby conductive materials, including, in some cases, a patient's body. These induced currents can lead to thermal effects, potentially causing burns or discomfort, particularly at the site of contact between the patient's skin and conductive objects such as leads or wires.

While other risks exist in the context of MRI—such as loss of signal, delayed imaging, or distortion of images—these are not directly linked to the time-varying magnetic fields in the same way that induced currents are. Loss of signal typically relates to technical issues with the MRI machine or patient movement, rather than the electromagnetic properties of the fields. Delayed imaging can arise from scheduling or operational inefficiencies, and distortion of images is often related to the interfacing of the magnetic field with certain materials rather than directly from the magnetic field itself. Thus, the primary risk from time-varying magnetic fields remains the generation of induced currents, which can pose a safety concern in the MRI environment.