The objective of the study is to assess the diagnostic efficacy (specificity and sensitivity) of 99mTc-4BOH SPECT myocardial perfusion imaging (MPI) compared to 13N-ammonia PET MPI in the detection of significant coronary artery disease (CAD) as defined by invasive coronary angiography (ICA).

The goal of this trial is to evaluate whether SPECT myocardial perfusion using the novel tracer 99mTc-4BOH is non-inferior to 13N-ammonia PET in diagnosing myocardial ischemia in patients with fractional flow reserve (FFR) as the diagnostic gold standard. In this study, 13N-ammonia PET imaging will be used as the positive control. Patients with diagnosed CAD who are scheduled for myocardial perfusion imaging will be assigned to undergo head-to-head SPECT imaging with 99mTc-4BOH and PET imaging with 13N-ammonia, with no more than 7 days between scans. All participants will subsequently undergo coronary angiography with FFR measurement within 30 days of imaging. The diagnostic performance of 99mTc-4BOH will be compared to that of 13N-ammonia, using FFR as the reference standard.

Inclusion Criteria:

• Age between 18 and 80 years. Presence of angina symptoms, such as chest tightness or chest pain. Coronary CT angiography (CTA) indicating ≥50% stenosis in at least one coronary artery.

Able and willing to provide written informed consent.

Exclusion Criteria:

• Underwent coronary revascularization (PCI or CABG) within the past 6 months. Presence of non-ischemic heart disease or left ventricular ejection fraction (LVEF) <35%.

Contraindications to adenosine stress (e.g., bronchial asthma, second-degree or higher atrioventricular block, severe hypotension).

Pregnancy or lactation. Unable or unwilling to sign the informed consent form.