A full-body PET scan exposes a person to a level of radiation roughly equivalent to smoking about 1,000 cigarettes. This comparison helps put the radiation dose from a PET scan into perspective by relating it to a more familiar risk factor—cigarette smoking.
To understand this, it’s important to know that a PET scan (Positron Emission Tomography) uses a radioactive tracer to create detailed images of the body’s metabolic activity. The amount of radiation from a full-body PET scan typically ranges around 25 millisieverts (mSv), though this can vary depending on the specific protocol and tracer used.
On the other hand, smoking cigarettes exposes the lungs and body to radioactive substances like polonium-210 and lead-210, which emit alpha and beta radiation. Studies estimate that smoking one pack of cigarettes per day for a year results in an accumulated radiation dose of about 13 mSv to the lungs. Since a pack contains 20 cigarettes, one cigarette roughly corresponds to about 0.65 mSv of radiation dose to lung tissue over time.
However, the radiation from smoking is chronic and cumulative, occurring over months or years, while the PET scan radiation is a one-time acute exposure. When comparing the two, a single full-body PET scan’s radiation dose of approximately 25 mSv is roughly equivalent to the radiation dose from smoking about 1,000 cigarettes (25 mSv divided by 0.025 mSv per cigarette, considering some estimates put the dose per cigarette lower).
This comparison is not exact because the types of radiation and their biological effects differ. The radiation from a PET scan is external and internal from the tracer, but it is controlled and targeted, whereas cigarette radiation is continuous and combined with many other harmful chemicals causing damage over time.
In simple terms, if you think about the radiation risk alone, having one full-body PET scan is like the radiation exposure you would get from smoking about 50 packs of cigarettes (1,000 cigarettes). This is a significant amount of radiation, which is why PET scans are used judiciously and only when medically necessary.
It’s also worth noting that the health risks from smoking come not only from radiation but from thousands of other toxic chemicals that cause cancer, heart disease, and lung disease. The radiation from a PET scan, while measurable, is just one part of the overall risk profile.
In summary, a full-body PET scan exposes you to radiation roughly equal to smoking around 1,000 cigarettes, but the nature and timing of the exposure are very different. This analogy helps illustrate why medical imaging involving radiation is carefully considered and balanced against its diagnostic benefits.
