What is a PET Scan?

Being diagnosed with breast cancer can be an overwhelming experience, and it's understandable to feel devastated and uncertain. During this phase, your doctor may be working on staging the cancer and devising an appropriate treatment plan, which may involve a PET scan. It may be helpful to familiarize yourself with the procedure, its functioning, possible side effects, and what to anticipate during the scan to alleviate any apprehension and prepare yourself mentally.

PET stands for positron emission tomography. It is a combination of nuclear medicine and biochemical analysis. It uses a radioactive tracer injected into the body to measure the metabolic activity of the cells in body tissues. It may be used to check organs and/or tissues for diseases.

The main components of PET are the radioactive tracer and the PET scanner. A few hours before the PET scan, the radioactive tracer is made in a nearby laboratory. The type of tracer made will depend on the type of organ(s) to be evaluated and their functions. A tracer is essentially a molecule that could be anything, such as glucose, protein, or hormone, and is made according to the type of metabolic activity to be measured. The tracer is made radioactive by combining a molecule with a radioactive atom (made by a cyclotron machine) in a biological molecule synthesizer.

The now radioactive tracer is then transported and injected into the patient’s bloodstream and will be allowed 30 to 60 minutes to spread in the body and into the tissues. During this time, the tracer will accumulate in the body's required parts, depending on the molecule it was made from. Cancer cells tend to be more active than normal cells surrounding them, causing the tracer to accumulate there. Over time, the radioactive atom in the tracer naturally decays and loses its radioactivity, releasing a positively charged subatomic particle called a positron (or a positive electron). When a positron and a negatively charged electron, found on all atoms, collide at the right speed, they combine and destroy each other. The energy is released as two gamma rays that travel in opposite directions out of the body.

The PET scanner, which looks like a ring surrounding the patient, detects these rays at opposite ends of the scanner and can locate where in the body the tracer must be. The scanner detects thousands of these events every second. With computer processing, three-dimensional visual images are produced, showing doctors where metabolic activity is taking place in the body, potentially locating a metastasized cancer or confirming the presence of cancer.

PET scans are an expensive test that requires special expertise to perform. As such, it is not used for breast cancer screening. Instead, it is more frequently used to evaluate people after a primary breast cancer has already been diagnosed. For example, it may be used to:

• Determine if the cancer has spread to the lymph nodes
• Determine if cancer has spread to other parts of the body and where in the body
• To assess metastatic breast cancer treatment response

While PET scans are generally safe for most people, there are a few possible risks:

• Allergic reaction

Allergic reactions to the radioactive tracer are rare, but if you experience symptoms such as difficulty breathing, sweating, and weakness, it's important to inform the radiographer immediately.

• Exposure to radiation

Although the radiation exposure is minimal, it could somewhat elevate the possibility of developing cancer. If this is worrying for you, it is advisable to consult a doctor for further discussion.

• Bruising

It's possible to experience some bruising near the injection site of the tracer, but do not worry, this is just temporary and typically clears up within a few days.

Other circumstances to take note of include:

• Pregnancy

Pregnant women are advised to avoid PET scans due to the slight radiation emitted by the radioactive tracer, which could be harmful to the developing fetus. However, in case of an emergency, the scan may be necessary.

• Breastfeeding

After injecting the radioactive tracer, it's typically not advisable for women who are breastfeeding to breastfeed for a while.

Prior to the PET scan, you will need to remove any jewelry or metal objects and put on a hospital gown. An hour before the scan, a radioactive tracer will be injected into your arm through an IV. This tracer will spread throughout your body and tissues for 30 to 60 minutes.

When it's time for the scan, you'll be taken to the scanning room and placed on a machine couch. Typically, patients lie on their backs during the scan. The radiographer will leave the room but can still see, hear, and talk to you.

During the scan, the couch will move slowly back and forth through the scanner. To avoid blurring the images, you must remain still. The scan is painless and relatively quiet, but let the radiographer know if you feel stiff or uncomfortable.

Once the scan is complete, the IV and urinary lines (if inserted) will be removed. You can then resume normal eating and drinking. The scan results will typically be available within one to two weeks.

It's natural to feel anxious before a PET scan, particularly if it's your first time. However, remember that the procedure is painless, brief, and can be highly beneficial for your treatment.