Nuclear imaging

Nuclear cardiology provides physiological information on myocardial perfusion and function. Three techniques are described: myocardial perfusion scintigraphy (MPS, the most widely used), radionuclide ventriculography (RNV) and positron emission tomography (PET). MPS is used to diagnose or exclude ischaemic heart disease, and is an option for functional assessment of suspected coronary disease, as specified in NICE guidance in 2016. It is validated in patients undergoing non-cardiac surgery, before and after coronary revascularization, and for assessment of myocardial viability. MPS relies on changes in cellular uptake of radioactive tracers at rest and during myocardial stress. Matched defects represent sites of infarction, whereas mismatch between normal perfusion at rest and reduced perfusion during stress indicates ischaemia. Cardiac risk is proportional to the size of the perfusion defect. RNV relies on blood pool labelling to assess ventricular function, and has excellent reproducibility. Cardiac PET has seen a recent increase in use due to improved techniques and new tracers. It employs positron-based tracers that resemble physiologically occurring compounds, to characterize myocardial metabolism, assess cardiac perfusion and viability, and assist diagnosis of intracardiac infection and sarcoid. Combining functional data from nuclear imaging with anatomical data from CT or MRI produces hybrid imaging, which improves diagnostic yield.