Ever been to a radiologist for an exam, and told you would have to remove all metallic substances from your person? If you watch the Medical TV series, House, you would have come across the episode where a man felt he was being pulled apart after he was placed in an MRI machine. The reason? He failed to tell the doctors that he had a metal plate in his head, put there after a prior accident.
Why is that the case? What have metals got to do with X-ray and other such medical diagnostic machines? Here are all the details you wondered about, and as told by about.com
Metal appears as a bright area on an X-ray, blocking visibility of underlying structures. The reason you are asked to remove metal is to give the radiologist an unobstructed view of the area of interest. Basically, you remove metal because it blocks anatomy. If you have a metal implant, obviously you can’t remove it for an x-ray, but if the technician is aware of it, he may position you differently to get the best imaging results or take x-rays from multiple angles.
The reason metal appears bright on the x-ray image is that it is extremely dense, so x radiation does not penetrate it as well as it does soft tissues. This is also why bones appear bright on an x-ray. Bones are more dense than blood, cartilage, or soft organs.
Unless the metal item is directly in the path between the x-ray collimator and the image receptor, there’s no issue having metal objects in the same room as an x-ray machine. On the other hand, metal objects are not permitted in a room housing magnetic resonance imaging (MRI) equipment because the objects will be drawn toward the powerful magnets when the machine is turned on.
