What is a common contraindication for MRI?

A common contraindication for MRI is the presence of ferromagnetic implants. This is primarily because MRI uses strong magnetic fields, which can interact with ferromagnetic materials. Implants such as certain pacemakers, aneurysm clips, or metal fragments might not only be affected by the magnetic field, potentially moving or heating up during the scan, but they can also disrupt the magnetic field itself and compromise the quality of the images.

In contrast, while allergic reactions can pose issues in other imaging modalities involving contrast agents, they are not specific to MRI. Previous radiation therapy generally does not affect MRI, as MRI does not use ionizing radiation. Chronic kidney disease may be a concern regarding the use of gadolinium-based contrast agents but does not inherently contraindicate an MRI scan itself. Thus, the presence of ferromagnetic implants stands out as a crucial reason for which an MRI would be contraindicated.