Anthropomorphic phantoms are finding wide use in evaluating the extent and severity of myocardial infarcts in patients. These phantoms serve as radiation equivalent and anatomically correct test subjects. This phantom, the Heart /Thorax phantom, has also proven useful providing valid assessments of mammoscintigraphy techniques. These phantoms serve to promote optimization of quantitative PET or SPECT imaging in patients. SPECT is a non-invasive method for diagnosing patients with coronary disease, but does not always provide optimum results. Image distorting effects such as photon attenuation, Comptom scatter, noise, and limitations in depth-dependent spatial resolution limit the ability of SPECT to provide images the fully represent true tracer distribution. This is particularly true of the non-uniform attenuation characteristics exhibited by the anatomy of the thorax, which often leads to sub-optimal results. These anthropomorphic phantoms therefore serve as highly useful instruments supporting on-going work to minimize SPECT's limitations.