Whereas CT scans and MRI look at the body's anatomy (bones, organs and other tissues,) PET scans look at how the body functions (how these organs and tissues are working.) With a PET scan, a small amount of radioactive sugar is injected into the bloodstream. Growing cells use sugar. Rapidly growing cells such as cancer cells take up the sugar and can be seen on 3-dimensional imaging.
PET scans can sometimes find lung cancer that has spread, but is not seen with other studies. Since surgery to remove primary lung cancer is not usually recommended for patients with metastatic cancer, the results of a PET scan might prevent unneccessary surgery.
Sources:
Giaccone, G. Fluorodeoxyglucose positron emission tomography, a standard diagnostic tool in lung cancer. Journal of the National Cancer Institute. 2007. 99:1741-43.
Tinteren, H. et al. Effectiveness of positron emission tomography in the preoperative assessment of patients with suspected non-small-cell lung cancer: the PLUS multicentre randomized trial. The Lancet. 2002. 359(9315):1388-92.
Ung, Y. et al. Fluorodeoxyglucose positron emission tomography in the diagnosis and staging of lung cancer: a systematic review. Journal of the National Cancer Institute. 2007. 99:1753-67.
