PET vs CAT

[harrie]

Can anyone tell me the difference between a PET scan and a CAT scan?

Thanks, Maryanne

[hutchibk]

CT, MRI and PET scans are all diagnostic tools to non-invasively (non-surgically) look inside the body. They are all based on the fact that certain things happen to atoms in our bodies when they absorb energy.

Positron Emission Tomography (PET) scans measure emissions from positron-emitting molecules. Because many useful, common elements have positron emitting forms (carbon, nitrogen, and oxygen), valuable functional information can be obtained. The PET shows molecular function and activity not structure, and therefore can often differentiate between normal and abnormal (cancerous / tumor) or live versus dead tissue. Because PET allows study of body function, it can help physicians detect alterations in biochemical processes that suggest disease before changes in anatomy are apparent with other imaging tests, such as CT or MRI. PET also can produce three dimensional images, and is usually used to compliment rather than replace the information obtained from CT or MRI scans.

CT or CAT(computerized tomography) uses a sophisticated X ray machine combined with a computer to create a detailed picture of the body’s tissues and structure. Usually a special dye called a contrast material will be injected prior to the scan. This makes it easier to see abnormal tissue due to specific absorption rates. It is often the preferred method for diagnosing many different cancers, including lung, liver and pancreatic cancer, since the image allows a physician to confirm the presence of a tumor and measure its size, precise location and the extent of the tumor's involvement with other nearby tissue. CT scans of internal organs, bone, soft tissue and blood vessels provide greater clarity than conventional x-ray exams.

Hope this helps. And then there are PET/CTs, which are a combination of the two scans.

[Sherryg683]

CAT scans will show an adnormal area, such as tumors, it can also show things that are not cancerous tumors, it does not distinguish between the two. Just shows something is there. PET scans uses the sugar dye contrast on the assumption that cancerous cells will absorb this sugar faster than normal cells and they will "light" up on the PET scan. Cons with just a PET scan alone is that there are many false positives, one study said up to around 48 percent. Usually these scans are used together. They lay the PET on top of the CAT scan and if an area that lights up on the PET, also shows a tumor area on the CAT then they are more likely to consider it indeed cancerous. A biopsy is usually need to determine cancer for sure...sherryg

[harrie]

Sherry and Brenda, thank you for your detailed explanations.
Maryanne