Cat Scan vs PET Scan

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Scaredy Cat

Cat Scan vs PET Scan

Postby Scaredy Cat » Thu Jan 11, 2007 11:53 am

What is the difference between a CAT Scan and a PET Scan?

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Postby sevenyear » Thu Jan 11, 2007 12:19 pm

From the standpoint of getting them , for the PET you are injected with radiactive sugar, wait an hour and the the PET shows activity whereever an active cancer absorbs the sugar rapidly (thus no exercise before the PET). A CT (with contrast) you are injected with iodine during the scan and drink a nasty contrast fluid an hour or two before the CT. The new CTs take only a few minutes and appear to measure density and density changes which may or may not be active tumors.. For example I recently had a liver tumor ablated. It still shows up as a dense fluid on the CT, however it does not appear on the PET since it is no longer an active tumor. Most newer PET scans also include a less accurate type of (than a contrast CT) CT scan on the same run.

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Postby Magnolia » Fri Jan 12, 2007 9:54 am

Pretty good description. A PET scan measures metabolic activity, and will show any areas that are actively eating up the radioactive sugar at an excelerated rate. Tumors do that. CT scans look at structures. They just show what masses are where. The radiologist has to figure out what all the images mean. The contrasts help differentiate some stuff from what's around it, but it can't tell what's malignant and what's not. My oncologist likes CT scans with oral, IV and rectal contrast because you get clearer pictures of potential masses. You can figure out what they are later. PET scans are good for initial staging to see if and where there is any spread, particularly to lymph nodes. Later, I think, CTs are good for looking for masses that might not have been there before.

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