A nuclear medicine scan is a diagnostic imaging technique in which a small amount of a radioactive substance (radioisotope or radiotracer) is injected into a vein or inhaled, and a specialised camera detects the radiation it emits to produce images of organ function and blood flow. Unlike structural imaging (CT or MRI), nuclear medicine scans show how organs are working at a physiological level.
In cardiac care, nuclear medicine scanning is used primarily for myocardial perfusion imaging, which assesses blood flow through the heart muscle at rest and during stress. This helps identify coronary artery disease and distinguish reversible ischaemia from permanent scarring after a heart attack. Common cardiac tracers include technetium-99m sestamibi and thallium-201.
Nuclear medicine studies can also evaluate ejection fraction via radionuclide ventriculography (MUGA scan), cardiac sarcoidosis or amyloid using specialist tracers such as PYP or DPD scans for cardiac amyloidosis, and pulmonary embolism via ventilation-perfusion (V/Q) scanning, where blood clots in the pulmonary circulation are identified as perfusion defects.
The radiation doses involved are low and comparable to other medical imaging. The radioisotopes used have short half-lives and are eliminated from the body quickly. Imaging typically takes 20 to 60 minutes. For detailed information on nuclear perfusion stress testing, see Radionuclide Studies and Thallium-201 Stress Test.
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