Is there any pain involved in a pet ct scan?

Not really: Pet-ct involves IV injection of a radiotracer, so there is a needle stick. Then, you have to lay in the scanner without moving for a while, which can be uncomfortable but shouldn't be painful.

Not really: The only discomfort should be related to needing an IV for the procedure. Otherwise you just lay flat on the scanning table.

Noisy: The machine is quite noisy and may intimidate some people. Also, claustrophobia may occur in some folks.

just an injection: Pet/ct is a scanner which looks a lot like a ct scanner. However, pet scans most often use a radioactive form of glucose, the energy source for most of the cells in our bodies. The pet scanner can detect and measure how much of the radioactive glucose analog, f-18 fdg, is in a particular organ or region. The areas using more glucose are hyper metabolic and generally more concerning.