Clinical definitions
As part of the baseline examination, clinical teams collected information on traditional cardiovascular risk factors, including age, gender, chest pain, smoking history, family history of CAD, diabetes, hypertension, and known CAD. Chest pain was classified according to the American College of Cardiology/American Heart Association 2002 guideline update on exercise testing [10]. Patients were considered as having diabetes if they were receiving treatment with oral hypoglycemic drugs or insulin. A family history of premature CAD was defined as a diagnosis of CAD in a first-degree relative prior to or at 55 years of age. Hypertension was defined as a blood pressure > 140/90 mmHg or use of anti-hypertensive medication. Hyperlipidemia was defined as total cholesterol level > 6.2 mmol/L or treatment with cholesterol lowering medication. Smoking history was defined as prior or current tobacco use. A patient was considered to have known CAD at the time of imaging based on a provided history of previously diagnosed atherosclerotic coronary disease, history of myocardial infarction (chest pain or equivalent symptom complex, positive cardiac biomarkers, or typical electrocardiographic changes), history of percutaneous coronary intervention, or history of coronary artery bypass grafting.