Since fMRI uses an MRI device, the standard preparations for an MRI procedure are necessary. For example, because the strong magnetic field used for MRI will pull on any ferromagnetic metal object implanted in the body, MRI staff will ask whether you have a heart pacemaker (or artificial heart valve), implanted port, infusion catheter (brand names Port-o-cath, Infusaport, Lifeport), intrauterine device (IUD), or any metal plates, pins, screws, or surgical staples in your body. In most cases, surgical staples, plates, pins and screws pose no risk during MRI. Red dyes used in tattoos and permanent eyeliner may contain metallic iron oxide and could heat up during MRI, however this is rare. You will be asked if you have ever had a bullet or shrapnel in your body, or ever worked with metal. If there is any question of metal fragments, you may be asked to have an x-ray that will detect any such metal objects. Tooth fillings are not affected by the magnetic field, but they may distort images of the facial area or brain, so the technologist should be aware of them. The same is true of braces, which may make it hard to "tune" the MRI unit to your body. You will be asked to remove anything that might degrade MRI images of the head, including hairpins, jewellery, eyeglasses, hearing aids, and any removable dental work.
The radiologist or an assistant may ask about drug allergies and whether head surgery has been done in the past. If you might be pregnant, this should be mentioned. Less than one in 20 patients who undergo MRI in an enclosed unit may feel confined or claustrophobic.