Radionuclide studies (also called nuclear cardiology tests or nuclear stress tests) are diagnostic imaging investigations in which a small amount of a radioactive tracer is injected into the bloodstream. As the tracer travels through the heart, a specialised gamma camera detects the radiation it emits and constructs detailed images of blood flow through the heart muscle.
The most common radionuclide test in cardiac care is myocardial perfusion imaging (MPI), which assesses how well different areas of the heart muscle receive blood supply. Images are taken at rest and during exercise or pharmacological stress (induced by medication such as adenosine or dobutamine). Areas of the heart that receive poor blood flow during stress but recover at rest suggest reversible ischaemia due to coronary artery disease. Areas that are permanently reduced suggest previous infarction (scarring from a past heart attack).
Radionuclide ventriculography (MUGA scan) can also be used to measure ejection fraction accurately, which is important for decisions about ICD implantation and heart failure management.
The radiation dose from radionuclide studies is relatively low and comparable to other medical imaging involving radiation. The radioactive tracer is typically excreted within hours to days. In the context of investigating cardiac arrest or unexplained arrhythmia, radionuclide studies may complement coronary angiography and echocardiography in the diagnostic workup.
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