Guest guest Posted December 20, 2000 Report Share Posted December 20, 2000 Hi, Stania, >There is another scan called PET..but I do not know any details In a nutshell: X-rays, including CT scans, look at dense structures - bones, joints, and to a lesser extent ligaments and tendons and internal organs. It can pick up infection in lungs only after the infection is severe enough to interfere with breathing. It can't see brains, lungs, etc. MRI looks at water distribution. Bones don't show up (little water in them); other tissues show up depending on how wet they are. Lipids - e.g. nerve sheathes, brain matter - show up less well than blood, muscle, etc. Eyes show up very well. SPECT and PET look at tracer isotope distribution. SPECT usually uses an isotope that shows blood flow. PET usually uses one that shows energy use (glucose uptake). A PET scan is a lot like a SPECT. It uses a radioactive isotope tracer, and detectors around the body to detect where the radioactivity goes. The difference is on the scientific end - PET is Positron Emmission Tomography, and the isotope is one that emits positrons, which quickly annihiliate with an electron to produce a pair of photon going directly away from each other. This allows a more accurate placement in space, so higher resolution. SPECT is Single Photon Emmission Computed Tomography - the radioisotope is one that produces gamma rays (like X-rays). It is like a 3-D gamma-ray camera. The radioactive exposure in these procedures is about the same, and is higher than X-rays but generally less than a radio-iodine test. Jerry _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com Quote Link to comment Share on other sites More sharing options...
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