Positron emission tomography (PET) for assessing myocardial viability
Positron emission tomography (PET) is usually taken as the gold standard for assessment of myocardial viability. PET scan with 13NH3 (ammonia) gives the perfusion while 18FDG (fluorodeoxyglucose) shows the metabolic activity of the myocardium. A mismatch between perfusion and metabolism whereby underperfused region of myocardium is shown to have active metabolism, is an indicator of myocardial viability.
The most important limitation of PET is its high cost and limited availability. It has some radiation risk when compared to echocardiography and cardiac magnetic resonance (CMR) imaging.
Important advantages of PET are that the validity is well established and it has an excellent sensitivity. PET can be done in patients with cardiac implantable electronic devices (CIED), while CMR is not suitable in that situation. Compared to single photon emission computed tomography (SPECT), PET has a better spatial and temporal resolution with better quality of pictures and less radiation risk.