A nuclear stress test is a diagnostic imaging procedure used to assess heart health, specifically how well blood flows to the heart muscle both at rest and during physical activity. This test involves a small amount of radioactive material, a common patient concern. Understanding how long this material remains in the body and how to minimize potential exposure to others is important.
Understanding the Radiotracer
The radioactive material used in a nuclear stress test is a radiotracer or radiopharmaceutical. It consists of a small, safe quantity of a radioactive isotope, such as Technetium-99m (Tc-99m) or Thallium-201 (Tl-201). When injected into a vein, this substance travels through the bloodstream and is absorbed by the heart muscle. As the radiotracer decays, it emits gamma rays detected by a special camera, often called a gamma camera. These detected signals are then used to create images of the heart, allowing healthcare providers to visualize blood flow and identify areas of poor perfusion or damage.
How Long Radioactivity Persists
The duration of radioactivity in the body after a nuclear stress test depends on the specific radiotracer used and its “half-life.” Half-life is the time it takes for half of the radioactive material to decay into a more stable form. For Technetium-99m, a commonly used radiotracer, the half-life is approximately 6 hours. Thallium-201, another radiotracer, has a longer half-life of about 73 hours (approximately 3 days).
Beyond radioactive decay, the body also eliminates the radiotracer through natural biological processes, primarily through urine and feces. This dual process means most Technetium-99m radioactivity is gone within 24 to 48 hours. Trace amounts from Thallium-201 may persist for a few days, or up to a week, but levels become negligible over time.
Minimizing Exposure to Others
Although radiation from a nuclear stress test is safe for the patient, practical measures can minimize potential exposure to others, especially vulnerable individuals. Staying well-hydrated by drinking plenty of fluids helps flush the radiotracer from the body more quickly through increased urination. Frequent urination and good hygiene, including thorough handwashing after using the restroom, are also recommended.
For a brief period, 12 to 24 hours after the test, avoid prolonged close contact with pregnant women, infants, and young children. This precaution helps ensure any residual, albeit small, radiation exposure to these sensitive groups is minimized. While the risk to others is low, these simple steps provide reassurance and safety.