You should not have an MRI if you have a cardiac pacemaker, a cerebral aneurysm clip, or electromagnetic devices such as insulin pumps. Some dental or eye implants should not be scanned, as well as metal fragments such as shrapnel or flecks of metal in the eye. Most prosthetic heart valves and orthopedic devices like joint replacements are safe, but you should check with your doctor. If you' re claustrophobic or have difficulty lying still in a confined space, be sure to inform your doctor or the radiologist before the procedure. There are sedatives that you can be given before the exam to help you relax during the procedure.
Some facilities also can give intravenous sedation when needed.
There is also an alternative to the traditional enclosed MRI scanner. This machine uses magnets above and below a table, which are supported by widely spaced columns. This leaves the sides of the scanner almost completely open, and decreases the enclosed feeling for the patient. The magnets for this type of scanner are weaker than the enclosed MRI scanner, which does affect the images that are produced. For this reason, the open scanner usually is only recommended for those patients who can't undergo the traditional scan.