What is the difference between MRI and CT Scan? – John Randal B. Cruz, 4-BS Physical Therapy

CAT/CT SCANS and MRIs are both diagnostic apparatuses that provide high-resolution pictures of any area of the body. They are big and intimidating machines that use computers to construct pictures of the internal organs. There are inherent differences in these tests’ mechanisms, as well as sophistication and applications.

CT scans were first developed and used in 1972. They were earlier known as CAT (computerized axial tomography) scans. According to Dr. Jay Nolasco of the MRI Department of the UST Hospital, CT scans consist of a highly sensitive x-ray beam focused on a specific plane of the body. As the beam passes through the body, it is picked up by a detector, which feeds the information into a computer. The computer then analyzes the information on the basis of tissue density. The analysis is fed into a cathode ray tube and a picture of the x-rayed cross-section of the body is produced. Bones show up as white, gases and liquids as black, and tissue as varying shades of gray, depending on density.

Magnetic resonance imaging (MRI) was first used in the late 1980s and its most sophisticated model in the country may be found in the USTH’s Division of Radiological Sciences. An MRI machine uses computer-controlled radio waves and large 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 creates a three-dimensional picture of the internal 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.

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MRI has no known associated health risks. However, people with pacemakers, aneurysm clips, or other implants that contain magnetic materials are generally advised not to undergo MRI testing. More sophisticated and detailed data can be learned from MRIs. MRI is best put to use in examining the central nervous system (the brain and spinal cord). It can also be used to identify tumors, strokes, degenerative diseases, inflammation, infection, and other abnormalities in organs and other soft tissues. And of course, one major difference is cost — MRIs cost a lot more than CT scans. John Ferdinand T. Buen


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