Physicians consider positron emission tomography, or PET scans, an effective method of diagnosing cancerous tumors and monitoring their stages of growth, the National Cancer Institute states. By conducting periodic scans, physicians can also determine whether a treatment is successfully eliminating a tumor or the cancer is likely to recur.
PET scans are primarily used to find organ malfunctions and abnormalities in the anatomical structure or chemical composition of cell tissue, according to Johns Hopkins Medicine. PET scanners detect the radioactive particles, or positrons, given off by a radionuclide that passes through the bloodstream. Physicians administer a radionuclide consisting of a radioactive atom and glucose or another natural chemical used by the target organ, allowing them to look for irregularities when the substance is metabolized. A computer produces a map of radioactivity with varying degrees of color to convey different rates of absorption.
Since cancer cells have a faster absorption rate than the surrounding healthy tissue, tumors usually have distinctly bright coloring on the scanner images, the National Cancer Institute notes. As patients receive treatment, physicians may perform successive scans to look for signs that the affected areas are absorbing glucose at a slower rate. Physicians value PET scans because they can often pick up on degenerative activity in cell tissue sooner than other imaging technologies, but this method is most effective when the tumor is larger than 8 millimeters. However, an accurate diagnosis requires using the combined results of multiple imaging techniques, including computed tomography, or CT, scans.