A Positron Emission Tomography, or PET, scan is a medical imaging technique that helps doctors evaluate the function of organs and tissues in the body. Concerns often arise regarding the safety of being around someone who has recently had a PET scan. This article aims to clarify the safety aspects for those around a patient after a PET scan.
Understanding Radiation from PET Scans
A PET scan uses a radiotracer, which is injected into the patient’s bloodstream. The most commonly used radiotracer is fluorodeoxyglucose (FDG), a sugar-like molecule with a small amount of a radioactive isotope, fluorine-18, attached. This tracer travels through the body and accumulates in cells that are highly active, such as cancer cells, allowing them to be visualized. The fluorine-18 in the tracer emits tiny particles called positrons. When these positrons encounter electrons in the body, they annihilate each other, producing gamma rays that a PET scanner detects. This process generates detailed images of how tissues and organs function. While the tracer is radioactive, the amount used is small and carefully controlled to ensure diagnostic accuracy with minimal exposure.
How Long Does the Radiation Last?
The radioactivity from a PET scan tracer does not remain in the body indefinitely. The radioactive component, typically fluorine-18 in FDG, has a “half-life.” This means that after a specific period, half of its radioactivity naturally decays away. For fluorine-18, the half-life is approximately 110 minutes, or just under two hours. The body also naturally eliminates the tracer, primarily through urine. This combined effect of radioactive decay and biological elimination means that by the next day, the level of radioactivity in the patient is negligible.
Safety Guidelines After a PET Scan
While the radioactivity quickly diminishes, healthcare providers recommend simple precautions for a short period. For most adults, normal interactions are safe immediately after the procedure. However, maintain a distance, such as three feet, from very young children and pregnant individuals for a few hours (typically 6 to 12 hours), as their developing systems are theoretically more sensitive to any radiation exposure. Practical steps include staying well-hydrated and urinating frequently to help flush the radioactive material, along with good hygiene like thorough hand washing, especially after using the restroom. These guidelines are short-term, and the overall risk to others is considered very low.