Positron emission tomography (PET) is an advanced nuclear medicine imaging technique that produces three-dimensional images of metabolic and physiological processes within the body. Unlike anatomical imaging (such as CT or MRI, which show structure), PET shows how tissues are functioning at a cellular level by detecting the radiation emitted by a radioactive tracer injected into the bloodstream.
In cardiac imaging, PET is used to assess myocardial viability and perfusion. The most commonly used tracer for cardiac PET is fluorodeoxyglucose (FDG), a radioactive form of glucose that is taken up by metabolically active (living) heart muscle cells. Areas of heart muscle that appear damaged or weakened on other tests but still show FDG uptake on PET are described as viable (hibernating myocardium): they may recover function if blood flow is restored by PCI or CABG surgery. Areas with no FDG uptake and no perfusion represent scar tissue and are unlikely to recover.
Cardiac PET can also use perfusion tracers (such as rubidium-82 or N-13 ammonia) to assess blood flow through the coronary arteries, both at rest and during pharmacological stress. It offers high sensitivity for detecting coronary artery disease and can quantify coronary flow reserve.
PET scanning requires specialist equipment and is available in a smaller number of NHS centres compared to radionuclide perfusion imaging. It is particularly useful in complex cases where other investigations have been inconclusive, and in guiding decisions about revascularisation in patients with severely impaired ejection fraction after cardiac arrest or heart attack.
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