PET Scan Test and Procedure

Overview

PET scans, also known as positron emission tomography, are advanced imaging tests in nuclear medicine. They reveal how tissues and organs work by highlighting their metabolic activity. A PET scan uses a radioactive tracer, most often injected into a vein, which travels through the body and gathers in areas with increased biochemical activity.

This method lets doctors see changes in the body before they appear on other diagnostic imaging tests like CT (computed tomography) scans or MRI (magnetic resonance imaging). PET/CT and PET/MRI scans combine different techniques to provide both metabolic and structural information, offering a more detailed picture.

Why This Test Is Ordered

Checking for Cancer

Doctors often use PET scans to look for cancer. The images highlight cancer cells, which usually absorb the tracer faster than healthy cells because of their increased metabolic activity. This feature makes it easier to spot tumors in the body, including areas like the brain, lung, breast, thyroid, skin, prostate, lymph nodes, and others. A PET scan can help:

Find where cancer may be.
See if the cancer has spread to other organs or tissues.
Monitor how well cancer treatment is working.
Look for signs that cancer has returned.

However, not every cancer shows up on a PET scan, and sometimes non-cancerous conditions may appear similar. Tumor types often checked:

Brain	Breast	Cervical	Esophageal
Lung	Pancreatic	Thyroid	Skin

Examining Heart Health

Doctors use PET scans to study blood flow to the heart muscle. They identify areas where blood does not flow well because of narrowed or blocked arteries. This information helps decide if procedures like angioplasty or bypass surgery are needed for conditions such as coronary artery disease.

Key Uses

Checking heart muscle function.
Detecting areas with low blood flow.
Guiding heart disease treatment plans.

Studying Brain Function

Doctors use PET scans to examine how the brain works. They spot disorders such as Alzheimer’s disease, tumors, and seizures. The scan shows how well different areas of the brain use sugar, highlights abnormal activity, and helps doctors understand the effects of various conditions.

Common Findings

Tumors or unusual growths.
Areas affected by epilepsy or frequent seizures.
Early changes related to dementias, including Alzheimer’s.

Possible Complications

A PET scan uses a small amount of radioactive material. This increases exposure to radiation, but the risk of serious side effects is low. Pregnant people face a higher risk as the radiation could affect an unborn baby. The tracer can also pass to infants during breastfeeding.

Some people might have allergic reactions to the tracer, though this does not happen often. Those with diabetes need to watch their blood sugar levels before the scan. Feeling nervous in small spaces (claustrophobia) can also make the test difficult for some. Always speak with a healthcare provider for guidance.

Potential Risk	Details
Radiation exposure	Small amount from the tracer.
Blood sugar changes	Especially important for diabetes.
Allergic reactions	Uncommon but possible.
Claustrophobia	May cause discomfort or anxiety.

How You Prepare

Before the scan, patients should tell their health professional if they have allergies, medical conditions like diabetes, or if they take any prescriptions, vitamins, or herbal products. They should also mention if they are pregnant, breastfeeding, or feel uneasy in tight spaces.

Preparation usually involves not eating for at least four hours beforehand. Plain water is typically allowed, but drinks with caffeine should be avoided. Patients should not engage in intense physical activity for at least 24 hours before the procedure.

Checklist

Inform staff of allergies.
Share a list of medications.
Report pregnancy or nursing.
Avoid caffeine.
Fasting (NPO) for at least 4 hours.
Refrain from strenuous exercise.

What You Can Expect

What Happens While the Scan Takes Place

Patients arrive, receive a hospital gown, and empty their bladder for comfort. A nuclear medicine technologist injects a radioactive tracer (such as FDG) into a vein in the arm or hand. Some people notice a cool feeling as the tracer enters.

The patient then sits or rests quietly for 30 to 60 minutes while the body absorbs the radiotracer. Using a PET/CT or PET-MRI scanner—which looks like a large upright ring or doughnut—the scan begins. The person lies on a narrow padded table that slowly moves into the center of the machine.

Key Points

Lying still is very important for clear, three-dimensional images.
The scanner may make clicking or buzzing noises.
Most people feel no pain, but some may feel anxious in the closed space.

Technologists remain nearby to offer help. If someone feels anxious, medicine may be available to help them relax. Most scans last about 30-45 minutes, depending on the type of scanner.

What to Know for After Your Scan

After finishing the scan, most patients can go back to their normal activities right away. Health professionals advise drinking extra fluids to help remove any leftover tracer from the body faster.

Step	What to do after the scan
Return activities	Resume usual routines
Drink fluids	Important for flushing tracer out

Follow any other advice given by the healthcare team. Most people do not need to stay in the hospital overnight.

Findings

After the PET scan, a radiologist studies the images and prepares a report. These findings help doctors understand if a condition is present, how advanced it is, and if any treatment is needed. The radiologist may use other imaging test results, such as MRI or CT, to support their evaluation and improve the accuracy of the diagnosis.

Step	Action Taken
Image review	Radiologist examines PET scan images.
Comparison	Other test results may support findings.
Outcome	Information helps in diagnosis and staging.