A Positron Emission Tomography (PET) scan is an imaging test that visualizes the body’s internal functions and biochemical processes. It helps detect diseases like cancer, neurological disorders, and heart conditions. Concerns about radiation exposure after a PET scan are common. This article clarifies these concerns and offers practical safety information.
How PET Scans Work and Radiation
A PET scan detects metabolic activity within the body’s cells. The process begins with injecting a small amount of a radiotracer (radioactive chemical) into a vein. This radiotracer mimics substances the body naturally uses, such as glucose.
The most common radiotracer is Fluorine-18 Fludeoxyglucose (18F-FDG), a glucose molecule with a small amount of Fluorine-18 attached. Cancer cells often have a higher metabolic rate, absorbing more glucose than healthy cells. Once absorbed, the Fluorine-18 decays by emitting positrons.
These positrons collide with electrons, producing gamma-ray photons detected by the PET scanner. A computer uses this information to create detailed 3D images, highlighting areas of increased metabolic activity as “hot spots.” This temporary radioactive material is the source of safety concerns.
Understanding Post-Scan Radiation Exposure
Radiation emitted after a PET scan is generally very low and diminishes rapidly. The radiotracer, such as 18F-FDG, has a short “half-life”—the time it takes for half its radioactivity to decay. For Fluorine-18, this is approximately 110 minutes (just under two hours).
This short half-life means the radiotracer quickly loses radioactivity, reducing potential exposure. The body also naturally eliminates the radioactive material, primarily through urine, reducing its presence. Drinking plenty of water after the scan can help flush the material out faster.
Total radiation exposure from a PET scan is comparable to several years of natural background radiation or some CT scans. For most individuals, general contact with someone who has had a PET scan is safe due to the low and rapidly decreasing levels of radioactivity. Most radiotracer activity is gone within several hours, and a person is typically considered non-radioactive the day after the exam.
Practical Safety Guidelines
After a PET scan, follow practical guidelines to minimize radiation exposure to others, especially vulnerable groups. Maintain a short distance from young children and pregnant individuals for a few hours. Healthcare providers often suggest limiting prolonged close contact for 6 to 12 hours.
Good hygiene is also important. This includes thoroughly washing hands after using the restroom and flushing the toilet twice for the first few hours. These measures prevent the spread of any residual radioactive material.
Patients should drink plenty of fluids to help excrete the radiotracer faster. While radiation levels are low and decrease rapidly, these simple precautions provide an additional layer of safety. Unless otherwise instructed, normal activities can typically resume after these initial precautions.
When to Seek Medical Advice
While PET scans are generally safe, seek medical advice in specific situations. If you experience unusual reactions after receiving the radiotracer, like an allergic reaction, contact your healthcare provider. Always inform your doctor about previous allergic responses to medical materials.
Concerns about prolonged exposure for very vulnerable individuals—such as a severely immunocompromised person, a newborn, or a breastfeeding infant—warrant discussion with healthcare professionals. Personalized guidance may be necessary regarding precautions. Breastfeeding mothers, for instance, might receive instructions about temporarily pausing breastfeeding.
If you receive conflicting information about post-scan safety or have specific anxieties, communicate with the imaging center or referring physician. Standard precautions suffice for most, but dialogue with medical staff ensures tailored advice.