Recent evidences have demonstrated improved diagnostic accuracy for detecting coronary artery disease (CAD) when myocardial blood flow (MBF) is quantified in absolute terms using single photon emission tomography (SPECT) compared to conventional myocardial perfusion imaging (MPI). However, there are no uniformly accepted cutoff values of MBF and MFR derived from SPECT for diagnosing hemodynamically significant CAD. Particularly, the diagnostic performance for quantitative SPECT has not been validated using fractional flow reserve (FFR). The aim of this prospective study is to determine optimal cutoff values of absolute MBF and MFR derived from NaI (Tl)-based SPECT and to evaluate the diagnostic efficacy of this quantitative technology utilizing invasive coronary angiography (ICA) in combination with FFR results as the reference standard in patients with suspected or known CAD.

Inclusion Criteria:

• Age 18 ~ 79 years old
• At least one CAD risk factor
• Intermediate to high pre-test likelihood for CAD
• Suspected or known CAD, clinically referred for invasive coronary angiography
• Able and willing to comply with the study procedures
• Written informed consent

Exclusion Criteria:

• History or risk of severe bradycardia
• History of myocardial infarction, dilated cardiomyopathy, hypertrophic cardiomyopathy, valve issue or congenital heart disease
• Wheezing asthma or COPD
• Known second- or third-degree AV block
• Known hypersensitivity to dipyridamole or adenosine
• Known coronary artery bypass graft (CABG) or percutaneous coronary intervention (PCI) prior to screening
• Breastfeeding or pregnancy
• Claustrophobia or inability to lie still in a supine position
• Unwillingness or inability to provide informed consent

Suspected or known CAD