15O-water is not metabolized in the body during a PET study. 15O-water diffuses freely across the cell membrane and is therefore the optimal flow tracer. It has a half-life of 122 seconds, which makes it possible to acquire multiple image scans in rapid sequence.
15O-water has been used as non-invasive gold standard for qualifying a number of methods including myocardial perfusion MR  and SPECT , FFR  and echo .
The short half-life of 15O-water further means that the patient radioactivity dose is the lowest achievable and down to 0.4 mSv pr. scan. The worldwide average natural dose to humans is about 2.4 mSv per year.
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This study measures the absolute myocardial blood flow using PET. It also discusses the characteristics of the radioactive tracers, that are available. It is shown that 15O-water is superior to the other tracers.
This comparative study shows that positron emission tomography (PET), using 15O-water as a tracer, exhibits the highest accuracy for diagnosis of myocardial ischemia.
”The availability of a reliable approved system for bed-side production of 15O-water could change 15O-water PET from an exotic research tool to a clinical workhorse”