Hybrid Imaging Current imaging is based largely on the use of a single modality, but combined or hybrid applications increasingly are available, which include both PET and CT or SPECT and CT, thus allowing for combined anatomic and functional testing. In addition, newer scanning techniques have allowed assessment of perfusion and FFR by CCTA alone, in addition to coronary anatomy.195 201 Notably, these combined assess- ments allow for a fused image in which the physiological assessment of flow is coupled with the anatomic extent and severity of CAD and also provides information on plaque composition and arterial remodeling. Limited evidence is available on hybrid imaging, although several reports have reported prognostic accuracy for cardiac events with both ischemic and anatomic markers.202 206 Other combinations of imaging modalities also are being developed, including PET/ CMR, which is currently a research application. The strength of combined imaging is the added value of anatomy guiding interpretation of ischemic and scarred myocardium as well as providing information to guide therapeutic decision making. Hybrid imaging also can overcome technical limitations of myocardial perfusion SPECT or myocardial perfusion PET by providing anatomic correlates to guide interpretative accuracy207 and can provide the functional information that an anatomic technique like CCTA or magnetic resonance angiography lacks; however, radiation dose is increased. 2.2.4. Diagnostic Accuracy of Anatomic Testing for the Initial Diagnosis of SIHD 2.2.4.1. 