A PET scan is a very advanced scan usually of the brain but also of other parts of the body, which actually looks at the body in action. So, a magnetic resonance image scan or an ordinary x-ray or a CAT scan looks at the body in a static way.
What can they see inside the body in terms of bones, muscles, and other tissues but they don’t see the functionality of the body. And what the PET scan does is that you get a radioactive chemical and that radioactive chemical is absorbed into your body and it allows the scan to observe your body in action. So, it’s used commonly these days to look for cancer. So let’s say you’ve been treated for cancer and the x-ray still shows a lump. The question is, is that lump dead tissue from the cancer in a successful part of treatment, or is there still live cancer tissue there? And the PET scan will often tell you whether or not there’s actually cancer there because it lights up in the PET scan because it’s a functional scan.
And for example, if you’ve got lung cancer, a PET scan is now standard procedure to see whether or not there’s tumour which can’t be seen by the x-ray which will determine whether or not you’ve got an operable cancer.