Ammonia (13N)

Ammonia (13N) is a radioactive isotope of ammonia used in medical imaging, specifically in positron emission tomography (PET) scans. It is produced by proton irradiation of water with cyclotrons and decays by positron emission to carbon-13.

Production

Ammonia (13N) is produced by the proton irradiation of water in a cyclotron. The protons are accelerated to high energies and then directed onto a target of water, where they interact with the oxygen atoms to produce nitrogen-13, which then rapidly decays to produce ammonia (13N).

Use in Medical Imaging

Ammonia (13N) is used in medical imaging to assess the perfusion of heart muscle. It is injected into the patient's bloodstream and then taken up by the heart muscle. A positron emission tomography (PET) scanner is then used to detect the gamma rays emitted by the decay of the ammonia (13N), providing a detailed image of the blood flow in the heart.

Decay

Ammonia (13N) decays by positron emission to carbon-13, a stable isotope of carbon. The emitted positrons interact with electrons in the patient's body, producing gamma rays that can be detected by the PET scanner.

Safety

As with all radioactive isotopes, care must be taken when handling ammonia (13N). However, its short half-life of approximately 10 minutes means that it rapidly decays to non-radioactive carbon-13, reducing the risk of prolonged radiation exposure.

See Also

• Positron emission tomography
• Radioactive isotope
• Cyclotron
• Proton irradiation

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