Which tracer is used to evaluate myocardial perfusion?

• A. 13N-ammonia
• B. 62Cu-ATSM
• C. 11C-methionine
• D. 18F-FDG

Answer: (A)

Evaluating myocardial perfusion is about showing how blood flows to different regions of the heart muscle. Nitrogen-13 ammonia is a PET tracer that is taken up by the myocardium in proportion to blood flow and gets trapped inside heart cells, so the resulting images directly reflect regional perfusion. Its rapid extraction and retention make it a reliable indicator of perfusion, though its very short half-life (about 10 minutes) means it must be produced on-site. The other tracers focus on different biology: copper-62 ATSM highlights tissue hypoxia; carbon-11 methionine tracks amino acid metabolism and protein synthesis; fluorine-18 FDG maps glucose metabolism. While FDG can be used alongside perfusion imaging to assess viability, it is not a perfusion tracer. Therefore, the tracer best suited for evaluating myocardial perfusion is nitrogen-13 ammonia.