Positron Emission Tomography (PET), one of the most valuable tools in cancer diagnosis, is a sophisticated molecular imaging technique which – by using a special scanner - displays the functional status of tissues in the body at the cellular level (their metabolism). It is a diagnostic scan that provides the physician with information not available with traditional anatomic studies such as computed tomography (CT) or magnetic resonance imaging (MRI). PET can detect changes in cell function (disease) long before they are evident as physical (anatomic) changes seen on CT or MRI (i.e. in cases where the CT or MRI appear normal).

In this way PET can add important information about many diseases allowing the physician to make a diagnosis often much earlier than with anatomic imaging techniques such as CT or MRI alone. In addition, in cases where an abnormality is noted on CT or MRI, PET can help differentiate benign (harmless) changes seen on CT/MRI from changes due to disease (malignancy). PET scanning also typically images the entire body, unlike CT/MRI which is usually broken up into specific limited body section scans.

With this information the physician is better able to determine the course of treatment for a particular disease state than if only CT or MRI data were available. In fact, this information can make a dramatic difference in a patient's recovery.

All cells use glucose as an energy sources but cancer cells use much more since they are growing much faster and out of control. This is the basis of imaging with F-18 FDG glucose, the radiotracer agent used in a PET oncology study. The abnormal, accelerated glucose (F-18 FDG) used by cancer cells is detected by the PET scanner that processes the emissions from the F-18 FDG glucose into three dimensional maps detailing regions of abnormally high levels of metabolism (tumor).

PET scanning is used in oncology specifically to stage malignancy, detect recurrence of disease, evaluate equivocal findings on CT or MRI imaging, and monitoring of response to therapy.

Some of the specific malignancies that PET is useful in diagnosing are: lymphoma, melanoma, solitary lung nodule, lung carcinoma, colorectal carcinoma, thyroid carcinoma, breast carcinoma, head and neck carcinoma, esophageal carcinoma, and many others.

Positron Emission Tomography is similar to other Nuclear Medicine studies and even Computerized Tomography (CT) in the amount of radiation received.

Once the test is completed, the radiopharmaceutical decays quickly and is essentially completely gone by the next day.

Patients with diabetes should advise the PET facility of their condition before the test is performed.

Patients who are pregnant or breast feeding should also inform the physician at the PET facility before taking the examination.

Patients need to fast for four to six hours before the procedure. At the time the scan is scheduled, further details will be provided about how to prepare for the procedure. Any other questions patients may have will be answered as well.

Films and Reports From Past Imaging Studies

Films from other imaging tests are very important and help expedite the reading of the PET study. Patients should bring all available material (reports and films) and have copies if available.

The study consists of an injection of a positron-emitting radiopharmaceutical (e.g., F-18 FDG), a drug that gives off radiation similar to that of other nuclear medicine diagnostic procedures. After being injected, the patient relaxes for 45 minutes to an hour in a quiet environment, with no reading or talking, while the radiopharmaceutical distributes in the body.

The patient is then placed in a special scanner that looks similar to a CT machine. The patient lies very still on a table that slowly moves through the scanner. The scanner detects the positron emissions from the injected FDG and reconstructs a three-dimensional map showing where the PET agent is concentrated in the body. This information will be valuable to the physician in making a diagnosis and prescribing a course of treatment, as well as assessing the response to therapy.

The actual scan takes from 70 to 90 minutes on average. Additional delayed views are occasionally obtained if necessary.