Person to be screened must be a male 40-65 yrs old or a female 45-70 yrs old. 

You can get a CT Coronary scan without a doctor's referral if you can answer yes to at least one of the following risk factors;

Diabetes
Current Smoker
Obesity
Family history of heart disease
Cholesterol level greater than 160/LDL
Blood pressure greater than 140/90