The use of radionuclide imaging is often a vital part of the imaging of ischemic heart disease. Stress myocardial perfusion imaging can be performed to detect relative perfusion defects, a sign of unbalanced coronary blood flow from significant stenosis. This test is frequently used and can identify ischemic territories, infer the distribution of coronary lesions, demonstrate fixed defects (infarcts), and quantify systolic function, each of which carries independent prognostic value beyond or in addition to the simple presence of ischemic myocardium. In certain situations, the test is limited, such as in cases of balanced ischemic lesions, obesity, and breast attenuation and diaphragmatic artifacts.4 Myocardial perfusion imaging can be performed with SPECT or PET. SPECT and PET can be used with radiotracers targeted at perfusion (eg, technetium-based and rubidium agents, respectively) and myocardial viability (eg, thallium and fluorine 18 fluorodeoxyglucose, respectively). Myocardial perfusion can be especially helpful in cases of known ischemic heart disease, a situation where quantitation of ischemic burden can be essential to guide management. Newer hybrid scanners (PET/CT and SPECT/CT) can offer simultaneous acquisition of nuclear and CT data, offering the benefits of calcium scoring, attenuation correction, and even anatomic CTA in conjunction with myocardial perfusion data.28 Case 1 (see Fig. 20–2) demonstrates rubidium PET and fluorodeoxyglucose PET in the workup for myocardial ischemia and viability, respectively. Advances in nuclear cardiology can include evaluation of ischemic memory with iodine 123–15-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (BMIPP) in which an area at risk of acute myocardial infarction can be detected as a defect even a couple of weeks after the myocardial insult.