Magnetic resonance imaging (MRI)
Magnetic resonance imaging may be the greatest breakthrough in modern medicine. It has allowed doctors to diagnose a whole host of medical conditions that they wouldn't otherwise be able to see. The great benefits of an MRI are that it can produce a very detailed image, much more detailed than an x-ray. It can also see all of the internal structure rather than just the bones like an x-ray can see.
Magnetic resonance imaging works by using a combination a giant magnet and radio waves to produce a very detailed image of the inside of the body. When you get an MRI you are placed inside of a large tube, this is the magnet. The magnet causes the nuclei of the hydrogen atoms inside your body to line up in a parallel rows. A radio wave is the pulsed this causes the hydrogen nuclei to be knocked out of that parallel alignment. They will quickly fall back into the parallel rows and when they do they will produce a radio signal. This is what shows up on the screen for the doctors to see.
Not only can an MRI produce a very clear image it can actually produce an image of all of the internal structures. That means that unlike an x-ray in which the doctor can only see the bones an MRI will allow him to see the internal organs as well. An MRI will produce a very thin cross section of the area that is being scanned that will allow a very detailed view of that area. This cross sections can then be combined together to produce a three dimensional image if necessary.
The other great advantage that an MRI has over an x-ray is the safety factor. Unlike x-rays there is no exposure to radiation. Neither the magnet nor the radio waves used on an MRI will cause any damage to the human body. That being said there are some people who can't use an MRI because of the effects of the magnet. This is mainly people who have had surgery that has required that metal be inserted somewhere. Things like pace maker or pins used to set broken bones will be ripped out by the powerful magnet so if you have had surgery you need to talk to the technologist before undergoing a scan.
Magnetic resonance imaging has a great number of uses in modern medicine but the most common are to allow doctors to see the inside of the brain and to look at the spine. These are area where it would otherwise be very difficult to make a diagnoses because there is no other way to see inside without exposing the patient to a great deal of risk. Other common uses are to study the joints and the abdomen again areas that aren't easy to see in other ways.