Excerpt

Assessment of myocardial perfusion under stress and rest conditions using various imaging modalities is the mainstay in the workup of coronary artery disease. Traditionally, the presence of relative regional perfusion defects has been the central concept behind myocardial perfusion imaging. Regional perfusion analysis is imperfect due to its relative nature, because the presence, severity, and extent of perfusion defects do not account for possible differences in absolute myocardial blood flow (MBF) at rest or stress. For example, if absolute flow is impaired globally (e.g., triple vessel disease), a comparison of the best and worst perfused regions will underestimate the severity of flow-limiting disease. Hence, information about absolute MBF and myocardial flow reserve (MFR) is desirable.1 Single-photon emission computerized tomography-myocardial perfusion imaging (SPECT-MPI) has traditionally been the workhorse for relative perfusion imaging, but several studies have shown that relative perfusion imaging may underestimate extent of disease.2,3 Furthermore, the ^99mTc flow tracers available for SPECT-MPI are limited by a relatively low first-pass extraction fraction at high flow rates, thus limiting the precision and accuracy of these tracers for estimation of myocardial perfusion especially during stress.4 …