Advances in coronary CT angiography and PET perfusion imaging for the detection of coronary artery disease

The diagnostic work-up of patients with suspected CAD involves a clinical evaluation estimating the probability of disease followed by a non-invasive imaging test. A myriad of non-invasive imaging modalities are available for this purpose and can be roughly divided into two groups, i.e. anatomical testing with coronary computed tomography angiography (CCTA) or functional testing using exercise testing or myocardial perfusion imaging. The aim of this thesis was to improve the diagnostic work-up of patients with suspected CAD through the investigation of advances in CCTA (Part I), [15O]H2O PET perfusion imaging (part II) and hybrid imaging (part III). Anatomical imaging using CCTA has emerged as one of the most widely used imaging modalities and both previous studies and studies from this thesis have demonstrated great diagnostic and prognostic performance of stenosis grading using CCTA. Studies from this thesis have shown that novel parameters obtained through post-processing of standard CCTA data, such as plaque measures, subtended myocardial mass, FFRCT and pericoronary fat attenuation may improve diagnostic and prognostic performance of CCTA. In addition to its role in the diagnostic work-up of patients with suspected CAD, a study from this thesis has demonstrated the feasibility of using CCTA for PCI procedural planning. Quantitative perfusion imaging using [15O]H2O PET has also gained great interest in the last decades. Previous studies and studies from this thesis have shown excellent diagnostic and prognostic performance of [15O]H2O PET-derived absolute quantification of myocardial blood flow. However, the addition of the longitudinal flow gradient to absolute myocardial blood flow did not improve the diagnostic performance of PET perfusion. Hybrid imaging with PET/CT has been proposed to combine the strengths and overcome the limitations of both separate techniques. Although recent studies and a study from this thesis have questioned the diagnostic potential of hybrid PET/CT imaging, data from this thesis suggest that comprehensive imaging incorporating PET-derived myocardial blood flow, CCTA-derived stenosis severity, and high-risk plaque morphology might result in an improved risk stratification. These promising findings urge for a prospective clinical trial with interventions based on hybrid imaging including anatomy, function and morphology. Hypothetically, combined anatomical and functional information from hybrid PET/CT may improve patient outcome by guiding the use of invasive coronary angiography and expensive medication to the highest risk groups and conversely avoiding overtreatment in patients without coronary atherosclerosis.