There are a number of diagnostic tests your doctor may order if he suspects you have cancer.
Specifically, if one level of radiographic technique, like an x-ray, has shown a suspicious mass, but the mass is too deep or too dangerous for safe biopsy, but whether or not the mass is cancerous or an infection, etc., the next level of radiographic technique will be ordered.
In many cases, this is a PET, or positron emission tomography, scan.
Strictly speaking, a PET scan is the detection of a radioactive emission called a positron that has been tied to a biologically active substance.
Usually the biologically active substance is a form of glucose. Cells need glucose, and when it is available, they will use it preferentially.
This means if you tie the radioactive particles to glucose, and then introduce that glucose solution into an area, the active cells will pick up the glucose solution, and burn it for energy, releasing the radioactive positrons that can be detected.
Computers can measure not only if positrons are being released, but also where and how, information that when taken together can be interpreted by the computer to produce a rather detailed image of the biologically active area in the body.
Biological activity is important because other masses that the body walls off, such as bacterial or fungal infections, are not biologically active as defined here.
At the end of the day, this means that a PET scan is one of the best ways to determine the difference between a cancerous tumor, which is biologically active, and a mass that may be noncancerous, like an infection.
To prepare for a PET scan, you will usually be asked to fast for a certain period of time before arriving at the testing facility. Once you arrive at the testing facility, you may be asked to change into a hospital gown.
An i.v. will be started, and you will be given the glucose solution with the radioactive markers in it. Then you will have to wait for a period of time, about 30 minutes to one hour.
At the end of that time, the scan will be performed. The scan itself will be painless and for the patient is the same experience as having a CT scan.
The chief differences are on the other end of the equipment, where the interpretive computers are located. Once the scan is finished, the i.v. will be discontinued. You may be asked to rest for a brief period, and you may be given something to eat or drink.
Certain medications can interfere with PET scans; your doctor will let you know if there are medications you need to suspend before or after the PET scan, and when you can resume taking them.