Coronary artery disease (CAD) is globally one of the leading causes of morbidity and mortality. CAD develops over decades when coronary arteries obstruct, typically causing chest pain symptoms and, in the worst case, death. Nowadays, obstructive CAD can be prevented and treated with modern and potent therapies; hence, accurate diagnostic tools have become more important. The aim of this thesis was to evaluate hybrid imaging techniques, i.e., combinations of two imaging techniques, for use in the detection of obstructive CAD. We evaluated the feasibility and accuracy of combined coronary computed tomography angiography (CTA) and either positron emission tomography (PET) myocardial perfusion imaging or coronary Doppler ultrasound to detect obstructive CAD in 107 symptomatic patents with an intermediate (30–70%) pretest probability of disease. Techniques were compared with invasive coronary angiography combined with physiological evaluation by fractional flow reserve. Our results showed that hybrid PET-CTA was highly accurate for detecting obstructive CAD and more accurate than either technique alone. Furthermore, measurement of myocardial blood flow by PET during vasodilator stress only was sufficient to evaluate the hemodynamic significance of coronary stenosis. We found that assessment of the coronary flow velocity profile at rest by Doppler ultrasound provides information on the hemodynamic significance of coronary stenosis identified by coronary CTA and may aid in detecting obstructive CAD. 
These results show the feasibility of hybrid imaging and demonstrate that it provides improved accuracy in detecting obstructive CAD as compared with standalone coronary CTA.