Description : CT scans and MRIs are both diagnostic tests that provide us with high-resolution pictures of the structure of any organ or area of the body which requires a thorough examination. Both tests take place in big, somewhat intimidating machines. They each use computers to construct pictures of the inside of the body. There are, however, inherent differences in these tests mechanisms, as well as sophistication and applications.

Basically, Computerised Tomography (CT)scans consist of a highly sensitive x-ray beam that is focused on a specific plane of the body. As this beam passes through the body, it is picked up by a detector, which feeds the information it receives into a computer. The computer then analyzes the information on the basis of tissue density. This analyzed data is then fed into a cathode ray tube (the device responsible for producing pictures on your TV screen), and a picture of the x-rayed, cross-section of the body is produced. Bone shows up as white; gases and liquids as black; and, tissue as varying shades of gray, depending on its densi ty.

Magnetic Resonance Imaging (MRI) was developed later than CT scanning, first being used in the late 1980s. An MRI machine uses computer-controlled radio waves and very big magnets, which create a magnetic field roughly 25,000 times stronger than the earth's magnetic field. After the machine creates a magnetic field, it sends radio waves into the body and then measures the response of its cells (how much energy they release) with a computer. From these responses, the computer is able to create a three-d imensional picture of the inside of the body. MRI makes use of the fact that all living cells have a certain magnetic quality to them; because of this, MRI can provide a look at the biochemistry of living cells.