Nuclear medicine has been available as an imaging technology first in the planar form and shortly thereafter as a tomographic technique. It is an extremely sensitive technique capable of measuring concentrations in the nanomolar to picomolar range. Using tracer technology, it provides functional information about many different organs and systems within the human body. The use of radioactive tracers in molecular imaging is widespread, both in preclinical and clinical use. This is primarily because tracers enable researchers to study nanomolar quantities of agents that target molecules of relevance in cancer pathophysiology. Tracers can also track other functional features of cancer, such as vascularity and oxygenation. This chapter introduces one of the nuclear medicine modalities: single-photon emission computed tomography (SPECT) and its hardware implementation. SPECT cameras or scanners utilize detection of gamma radiation, hence frequently they are referred to as gamma cameras. The SPECT detector must combine conflicting requirements: good intrinsic efficiency, good energy resolution, and good spatial resolution at reasonable cost. These requirements are best met with the direct conversion material cadmium zinc telluride (CZT). CZT sensors use small, pixelated anodes for achieving good spatial resolution and large CZT thickness for excellent detector efficiency reducing examination scan times dramatically compared to traditional scintillator-based scanners. Single-photon emission computed tomography (SPECT) technology for myocardial perfusion imaging (MPI) has improved remarkably during the last several years. New solid-state cardiac camera systems using cadmium zinc telluride (CZT) detectors combined with novel collimator designs have been introduced, including the D-SPECT (Spectrum Dynamics, Caesarea, Israel) and NM Discovery 530/570c (General Electric Healthcare, Haifa, Israel). This chapter provides a description of both scanners.