Society of Nuclear Medicine Procedure Guideline for Myocardial Perfusion Imaging

Myocardial perfusion imaging (MPI) utilizes an intravenously administered radiopharmaceutical to depict the distribution of nutritional blood flow in the myocardium. Perfusion imaging identifies areas of reduced myocardial blood flow associated with ischemia or scar. The relative regional distribution of perfusion can be assessed at rest, cardiovascular stress, or both. Imaging can also be performed during acute events (e.g., chest pain of unknown etiology, such as in the coronary care unit or emergency department). Perfusion images can be recorded with planar or tomographic single-photon or tomographic positron imaging techniques, utilizing radiopharmaceuticals that are extracted and retained for a variable period of time by the myocardium. The data can be analyzed by visual inspection and/or by quantitative techniques. Some radiopharmaceuticals employed for MPI and approved by the U.S. Food and Drug Administration (FDA) include: Tl201 and the Tc-99m–labeled radiopharmaceuticals, such as sestamibi, tetrofosmin, and teboroxime, for single-photon imaging and Rb-82 for PET imaging. Patients with significant coronary artery narrowing as a result of coronary artery disease (CAD) and/or abnormal coronary flow reserve will have a zone of diminished radiopharmaceutical concentration in the area of decreased perfusion. If either the area or severity of decreased tracer concentration is worse when the tracer is administered during stress than rest, the zone of decreased tracer concentration most likely represents ischemia. If the area of diminished tracer concentration remains unchanged, even after injection at rest, the defect most likely represents scar, although in a significant number of cases, it may represent viable, underperfused myocardium.*In addition to regional perfusion, recording the data with both SPECT and ECG gating permits calculation of global and regional ventricular function and assessment of the relationship of perfusion to regional function.