PET-CT is a new imaging tool that combines two scan techniques in one exam - a PET scan and a CT scan. The information from the PET scan and from the CT scan are different but complementing to each other.
The PET scan shows areas with increased metabolic activity, while the CT scan shows detailed anatomical locations. A combination of these two images together enables a doctor to tell whether a region with high metabolic activity is significant, and if so, to state definitively where that location is.
PET-CT is mainly used for diagnosis, staging or restaging malignant disease and metastases and evaluation of treatment response. Often the PET-CT is repeated to monitor the effect of treatment of a particular disease. Most commonly PET utilizes F18-FDG as a radiotracer, the short half life of which (110 min) reduces radiation exposure compared with other commonly used radionuclide such as 99mTechnetium (6 hours) and 201Thallium (72 hours).