Positron emission tomography, also known as a PET scan, is a diagnostic test that captures images of biological functions. The images provide information about cell biochemistry and metabolism that can help diagnose a variety of diseases and other conditions. PET imaging measures energy emitted from a radioactive substance that is ingested prior to the procedure. The injected material, detected through radioactive particles called positrons, interacts with body tissue to produce gamma radiation, which provides information about cell biochemistry and metabolism.
A PET scan measures important body functions, such as blood flow, oxygen use, and glucose metabolism, which help doctors evaluate how well organs and tissues are functioning and in some cases, diagnose a variety of diseases and other problems before physical damage occurs.
The Purpose of a PET Scan
Images from a PET scan can show detailed information on the size, shape, position and function of organs. It is extremely useful in detecting, abnormalities, diagnosing disease and monitoring treatment. A PET scan may be used to:
- Examine brain function
- Diagnose cancer
- Monitor the effectiveness of cancer treatment
- Determine whether cancer has spread to other areas of the body
- Diagnose heart problems and brain disorders
- Diagnose diseases such as Alzheimer's
- Determine blood flow to the heart
A PET scan may also be used to evaluate brain abnormalities such as tumors, seizures and memory disorders.
The Benefits of a PET Scan
PET scans of the whole body may be used to determine the progression of cancer and the effectiveness of cancer treatment. Scans of the brain can aid in the diagnosis and treatment planning for memory or seizure disorders and brain tumors. While scans of the heart are commonly performed to measure blood flow, detect signs of coronary artery disease and determine whether damaged heart muscle is permanently scarred or able to be treated with surgery.
PET scan results are often the most valuable information used when making a diagnosis, because they can identify changes in the body at a cellular level. A PET Scan often eliminates the need for exploratory surgery.
The PET Scan Procedure
Patients may be asked to abstain from eating or drinking for several hours before a PET scan, since it may affect the activity of the tracer substance. All metal objects, including jewelry, eyeglasses, hearing aids and hair clips, must be removed prior to the exam.
Prior to the procedure a radioactive material called a radiotracer is given to the patient by mouth or injection. It may take about one hour for the radiotracer to travel through the body and be absorbed. After the tracer is absorbed, the patient lies down on the scan table and is moved into the tunnel of the PET scan machine. An array of ring-shaped detectors measures the emission of positrons as the tracer interacts with body tissues. These detectors move around the body and produce images that appear on a computer screen. A PET scan takes about 30 minutes to complete.
Risks of a PET Scan
While a PET scan is considered a safe procedure that results in very low radiation exposure, there are minimal risks which may include:
- Allergic reaction to radioactive materials
- Pain or soreness at the injection site if the tracer is administered intravenously
Women should inform their doctor if they are pregnant or nursing before undergoing a PET Scan. A PET Scan is an effective diagnostic test that offers detailed information for the structure and functions of tissue and organs that is not available in other imaging procedures.