What are some contraindications to performing MRI?
There are numerous contraindications to MRI for which patients should be screened prior to imaging  . Absolute contraindications have historically included pacemakers/defibrillators, metallic foreign bodies in the eyes, deep brain stimulators, cerebral aneurysm clips, cochlear implants, Swan-Ganz catheters, and bullet fragments. The risks of performing MRI when these devices or implants are present include tissue heating, device movement, or device damage resulting in malfunction or necessitating replacement. Relative contraindications exist when certain types of implants, such as cardiac prosthetic valves, have been acutely implanted (e.g., less than 4 to 6 weeks). More recently, it has become possible for patients with pacemakers/defibrillators to undergo MRI in a controlled setting  . New devices are continuously being developed that are MRI-safe or MRI-compatible (safe under specific scanner settings and configurations). http://www.mrisafety.com provides a regularly updated comprehensive database regarding which devices are MRI-safe or MRI-compatible.