These isotopes are used in positron emission tomography, a technique used for medical imaging. The energy emitted depends on the isotope that is decaying; the figure of  applies only to the decay of carbon-11.
The short-lived positron emitting isotopes C (T = ), N (T = ), O (T = ), and F (T = ) used for positron emission tomography are typically produced by proton irradiation of natural or enriched targets.