Putting the Low Radiation of 15O-Water in Perspective

Tracers are radioactive compounds that doctors inject into patients to diagnose various diseases by, for example, following the flow of blood or use of sugar in organs. All tracers come with a radiation dose, but the dose of 15O-water is much lower than all other tracers used in cardiology. 15O-water is therefore among the safest tracers to use. To put it simply, the amount of radiation from one 15O-water dose (0.46mSv) is about the same as 1.5 months of natural background radiation that we are all exposed to as part of our daily living.


Ionizing radiation is frequently used for medical imaging, as it makes it possible to look inside the body. There are some harmful side-effects of too high a dose of radiation, which forces us to think carefully about when to apply it. The easiest way to determine this is to look at the radiation dose associated with a procedure: if the dose is low, the risk is low, and the procedure can be applied more freely.

Cardiology makes use of many procedures with ionizing radiation, including CT angio, PET, SPECT and invasive tests (ICA). However, it is accepted that the (low amount of) radiation in cardiology is much less of an issue than not properly treating a patient’s heart.

We compared the radiation dose of 15O-water with other procedures used in cardiology and with some sources of radiation in daily life, to illustrate how low the dose of 15O-water is.

Figure 1: Radiation doses from cardiac imaging procedures

Comparison with other tracers and tests

In Figure 1 you can see how the dose of a single injection of 15O-water compares to that of other commonly used PET tracers or cardiac procedures.

Compared to the clinical workhorse, SPECT, the radioactive exposure is 17x lower.

Radiation in our daily living 

A normal annual radiation dose from natural sources (cosmic rays, radioactive materials in the ground) is on average 3.25 mSv in the US (source: EPA), the equivalent of eight 15O-water injections.

The average total radiation dose for a US citizen, including from human sources, is 6.2 mSv (source: NRC) or fourteen 15O-water injections. In addition, people are exposed to additional radiation during air travel, with one 15O-water injection being equal to about six return flights London-New York. Last, one 15O-water injection is also about the radiation dose of eating 4,000 bananas.