Coronary artery disease results in narrowing of the blood vessels supplying oxygenated blood to the heart muscle. Diagnosis in patients with symptoms of chest pain is now quickly done with CT coronary angiography. This x-ray test can show narrowed blood vessels but has limited ability to predict the severity of the narrowings in some cases. We have described a new approach using PET exercise 18F-FDG imaging as a method to image areas of heart muscle not getting enough blood during exercise stress. The 18F-FDG images are co-registered with the CT anatomy from the CTA to provide direct evidence of the consequences of the narrowing.