 The PET scan is a nuclear medicine imaging study that measures how much radioactive sugar is used by your tumor. The study will compare pictures of the cancer from the PET scan to other x-ray exams, such as a CT scan, as well as to what your doctors find at the time of surgery. If the study results show that the PET scan gives us a good idea of what is happening to the tumor, then it may be useful in deciding which patients with colorectal metastases to the liver should be operated on and what operation should be performed. 