13N-Ammonia is commonly used to assess which parameter?

• A. Cerebral blood flow
• B. Myocardial perfusion
• C. Renal filtration
• D. Pulmonary ventilation

Answer: (B)

The main idea is that this tracer is a PET imaging agent whose uptake in tissue reflects blood flow, making it especially suited for measuring how much blood is reaching the heart muscle. In the myocardium, ammonia is rapidly extracted from the blood and largely retained, so the PET signal corresponds to myocardial blood flow. This allows clinicians to assess myocardial perfusion and identify areas with reduced flow or ischemia. It’s not typically used for brain perfusion, renal filtration, or pulmonary ventilation, which rely on other tracers or methods.