Perfusion Imaging and CT -Understanding Relative Efficacy

This study is a prospective, multi-center, within-subject comparative study. One hundred fifty (150) subjects with CATH procedures are needed in the study. Approximately 300 subjects who meet all of the inclusion/exclusion criteria will be enrolled. The study population will consist of subjects with symptoms suspected of and at intermediate-risk for ischemic heart disease, which are referred for MPS for a definitive diagnosis of CAD. Each subject will undergo the following procedures: * A Myocardial Perfusion Study (MPS) procedure, as standard of care; * An IV contrast-enhanced cardiac CT (CCTA) procedure; * A CATH procedure when the MPS and/or cardiac CT examination is deemed positive or equivocal and at the discretion of the referring physicians, as a standard-of-care procedure. When both the MPS and CCTA are normal, the subject is not required to undergo a CATH procedure, but will enter into follow-up. The research staff at each site will perform follow-up for each subject at 12 months (± 15 days) and 24 months (± 15 days) and 36 months (± 15 days) after the completion of the cardiac CT procedure.