CHAPTER 18: NUCLEAR CARDIOLOGY

OVERVIEW

Nuclear cardiology is an integral part of routine cardiovascular practice. This chapter provides a synopsis of nuclear cardiology procedures and the published evidence of their role in the diagnosis, risk assessment, and management of patients with suspected or known coronary artery disease (CAD). In the technical section, the focus is on single-photon emission computed tomography (SPECT) since positron emission tomography (PET) is the subject of Chapter 19. Guidelines and appropriate use criteria combine SPECT and PET, and considerations of the applications are similar; therefore, the clinical portions of this chapter discuss both approaches. While nuclear cardiology has a broad potential role in molecular imaging, myocardial perfusion imaging (MPI) with SPECT and PET makes up the vast majority of current clinical nuclear cardiology procedures; hence, MPI is the primary subject of this chapter. In the chapter, CAD generally refers to the presence of an obstructive stenosis, in contradistinction to coronary atherosclerosis, which is used to denote the presence of any atherosclerotic plaque in the coronary arteries. The term nuclear MPI will be used when the discussion refers to both SPECT and PET-MPI approaches.

Historical Perspectives in Nuclear Cardiology

The roots of nuclear cardiology began with the assessment of radioactivity transit times in the central circulation in the 1920s,¹ followed by clinical assessment of cardiac output in the late 1940s.² The Anger scintillation camera, the imaging device still used today for the majority of all nuclear cardiology procedures, ushered in the practical clinical use of nuclear cardiology in the late 1960s by providing images of the cardiac distribution of radioactivity. The commercial availability of thallium-201 (²⁰¹Tl) in 1976 initiated the broad application of clinical MPI. In the early 1980s, SPECT, using a rotating Anger camera detector, became widely available, increasing the ability to localize and quantify regional myocardial perfusion defects. In 1990, technetium-99m (^99mTc)-sestamibi was approved for use in the United States, followed shortly thereafter by ^99mTc-tetrofosmin. The higher myocardial count rates of the ^99mTc agents made it possible to perform electrocardiogram (ECG)-gated SPECT-MPI by obtaining images from the different parts of the cardiac cycle (gated SPECT). By 2003, more than 90% of SPECT-MPI used gated SPECT, providing routine objective clinical assessments of rest and stress myocardial perfusion and function.³ PET scanning became available in the early 1980s and its application for myocardial viability using ¹⁸F-Fludeoxyglucose (FDG) and MPI with ¹³N-ammonia and ¹⁵O-H₂O was described soon thereafter. In the early 1990s, rubidium-82 (⁸²Rb), a generator-produced PET radiopharmaceutical, became available, broadening clinical adoption of PET-MPI as well as opening the possibility of dynamic SPECT-MPI to quantify bloodflow.

There has been an evolution over time of the applications of clinical nuclear cardiology, roughly corresponding to the decades since its introduction. In the 1970s, nuclear cardiology procedures were validated for the detection of CAD, and their application was ...