The benefit of the information obtained from a nuclear stress test, when done appropriately, far exceeds any danger from radiation exposure. However, pregnant women should not have a nuclear scan, and patients who have several procedures that involve radiation exposure should discuss the issue with a doctor, so that the total dose does not exceed safe limits.
When doctors and physicists talk about radiation exposure to the human body, they often use millisieverts (mSv) as the measurement. Each year, Americans are typically exposed to a radiation dose of about 3 mSv, just from the atmosphere. By comparison, a chest x-ray delivers a radiation dose of 0.02 mSv.
Nuclear stress tests expose patients to a larger dose, but it is not considered to be dangerous. For example, one of the most common types of nuclear stress tests - a resting scan combined with a stress scan using the radioactive tracer technetium-99m sestamibi - averages 11.3 mSv. A rest-stress scan using the radioactive tracer technetium-99m tetrofosmin averages 9.3 mSv. In both cases, that is about 500 times the dose that comes from a chest x-ray.
Doses are much higher for nuclear stress tests that use the radioactive tracer thallium-201 - about 22 mSv with a single injection of thallium. Some cardiologists prefer to use a double-injection protocol with two different radioactive tracers. When thallium and technetium-99m sestamibi are combined, the radiation dose averages about 29.2 mSv.
We all want to keep our exposure to radiation to a minimum. But it is also important to remember that medical tests can provide valuable and sometimes life-saving information, so the risks of radiation exposure must always be weighed against the benefits.