Nuclear imaging

Nuclear cardiology is a well-established technique that provides physiological information regarding 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 chiefly in the diagnosis or exclusion of coronary artery disease, and is an option for the functional assessment of suspected coronary disease in those at an intermediate risk, as specified in the NICE guidance of 2010. It has also been validated in patients undergoing non-cardiac surgery, before and after coronary revascularization, and in the assessment of myocardial viability. MPS relies on the 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 regional ventricular function with excellent reproducibility. Cardiac PET has seen a recent surge in interest, with improved techniques and new tracers leading to an expansion of its use. It uses positron-based tracers that closely resemble physiologically occurring compounds, so it can characterize myocardial metabolism, assess cardiac perfusion and viability, and assist the diagnosis of intracardiac infection and sarcoid.