Among the current myocardial CT perfusion techniques, dynamic CT perfusion technique is most advantageous in obtaining information on myocardial blood flow and volume. However, dynamic CT perfusion technique involves higher radiation dose than static CT techniques. Patients have to take a breath hold during 30 seconds with current dynamic CT perfusion protocol. If patients cannot hold their breath, anterior or inferior myocardium might be excluded due to limited scan coverage of a 128-slice dual-source CT scanner.

Reduction of scanning duration of dynamic CT perfusion may not only reduce radiation exposure, but also make patients more comfortable. Therefore, the investigators intended to propose a modified scan protocol with shorter scan duration and compare diagnostic accuracy of a modified scan protocol with the current scan protocol.

The aim of this study is to compare the diagnostic performance of adenosine-stress dynamic myocardial CT perfusion using a reduced dynamic scan duration with perfusion protocol of 30-second scan duration for the detection of myocardial perfusion defect and significant coronary artery stenosis.

This trial is a single center, prospective, randomized trial designed to compare diagnostic performances and radiation doses between two protocols with 30-second or 21-second dynamic scan durations. A total of 120 symptomatic patients will be randomized to dynamic CT perfusion protocols with 30-second or 21-second scan duration. They will also undergo 1.5-T MRI and invasive coronary angiography as reference standards for the assessment of myocardial perfusion and coronary artery stenosis. The primary end point of the study is to compare diagnostic performances between two CT protocols of dynamic CT perfusion. The secondary endpoint of this study is to compare radiation doses and image qualities of two scan protocols.

Inclusion Criteria:

1. Men and women patients, with age ranging 30-80.
2. Known or suspected coronary artery disease who are supposed to undergo invasive coronary angiography
3. Patients who are willing to sign the informed consent form

Exclusion Criteria:

1. Contraindication of CT

   • Known allergy to iodinated contrast media or history of contrast-induced nephropathy
   • Decreased renal function: elevated serum creatinine (>1.5 mg/dl)
   • Severe arrhythmia: atrial fibrillation or uncontrolled tachyarrhythmia, or advanced atrioventricular block (second or third degree heart block)
   • Severe thyroid disease
   • Homocystinuria
   • History of asthma
   • Hypersensitivity to adenosine
   • Severe obstructive lung disease
   • Intake of caffeine or xanthine-containing compounds within the last 48 hours

2. Contraindication of MRI

   • Claustrophobia
   • Metallic hazards
   • Pacemaker implant
   • eGFR (estimated glomerular filtration rate) <30 ml/min
   • Clipping for aneurysm (stainless steel clips), neurostimulator, cochlear implant.

3. Unstable or uncooperative patients

4. Limited life expectancy due to cancer or end-stage renal or liver disease

5. Evidence of severe symptomatic heart failure (NYHA Class III or IV)

6. Acute myocardial infarction, hypertrophic cardiomyopathy, dilated cardiomyopathy, coronary artery bypass surgery, or other cardiac surgery

7. Women with positive pregnancy tests