MR Unsafe is one of three internationally recognised safety labels applied to medical devices, implants, and equipment to describe their behaviour in a magnetic resonance imaging (MRI) environment. A device labelled MR Unsafe presents unacceptable risks to the patient or others when brought into or used within the MRI scanner room. These risks can include movement or heating of the device due to the strong magnetic field, which can cause serious injury or death.
The three MRI safety classifications are: MR Safe (the device poses no known hazards in any MRI environment), MR Conditional (the device is safe under specific tested conditions including defined field strength, scan duration, body region, and other parameters), and MR Unsafe (the device must not enter the MRI environment under any circumstances).
This classification is particularly important for people with cardiac implants. Traditional pacemakers and ICDs were historically labelled MR Unsafe, making MRI scans impossible for these patients. Most modern cardiac devices are now labelled MR Conditional, meaning MRI can be performed safely provided strict protocols are followed, including programming the device to a safe mode before scanning, using an approved field strength (usually 1.5 Tesla), and limiting scan time and specific absorption rate.
Patients with a pacemaker or ICD who need an MRI scan should inform their radiographer and cardiac physiologist well in advance. The cardiac device clinic will check the device model, confirm its MRI classification, and if it is MR Conditional, arrange device reprogramming for the scan. Patients should carry their device card at all times, as it contains the information needed to make these safety decisions quickly.
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