When it is time for your scan, you may first go to a cubicle to take off your outer clothing down to your underwear and put on a hospital gown. Don't forget to remove jewellery, watch and hair clips. If you are just having an MRI of your head, you may not have to undress. The scan uses a very powerful magnet.RI stands for magnetic resonance imaging. This type of scan uses magnetism and radio waves to build up a picture of the inside of the body. Below is an example of an MRI scan of the head.