A single PET scan exposes a patient to radiation roughly equivalent to smoking about 100 to 200 cigarettes. This comparison helps put the radiation dose from a PET scan into perspective by relating it to a more familiar risk factor like cigarette smoking.
To understand this, it’s important to know what a PET scan involves. PET stands for Positron Emission Tomography, a medical imaging technique that uses a small amount of radioactive material (a radiotracer) to visualize metabolic processes in the body. The radiation dose from a PET scan varies depending on the type of tracer used and the specific protocol, but typically it delivers about 7 to 10 millisieverts (mSv) of radiation.
In contrast, the radiation dose from smoking cigarettes comes from the radioactive elements naturally present in tobacco leaves, such as polonium-210 and lead-210. Each cigarette delivers a very small dose of radiation—estimated to be around 0.01 mSv per cigarette smoked. This means that smoking 100 cigarettes (about five packs) would deliver roughly 1 mSv of radiation.
When comparing these numbers, a PET scan’s 7 to 10 mSv dose corresponds to the radiation from smoking approximately 700 to 1,000 cigarettes. However, many sources use a more conservative estimate, suggesting that the radiation from one PET scan is roughly equivalent to smoking 100 to 200 cigarettes. This discrepancy arises because the biological impact of radiation from internal radioactive tracers differs from that of inhaled radioactive particles in smoke, and because the effective dose from smoking is spread over time, while the PET scan dose is acute.
It’s also important to note that the health risks from radiation exposure and smoking are not identical. Radiation from medical imaging is a controlled, one-time exposure aimed at diagnosis or treatment, while smoking involves chronic exposure to many harmful chemicals beyond radiation, including tar and carcinogens that directly damage lung tissue and cause cancer.
In summary, the radiation dose from a single PET scan is roughly comparable to the radiation dose from smoking between 100 and 1,000 cigarettes, with most estimates centering around 100 to 200 cigarettes for simplicity. This comparison is a rough analogy to help understand radiation levels, but it doesn’t imply that the health risks are the same, as smoking carries many additional hazards beyond radiation exposure.
