Dynamic Myocardial Computed Tomography Perfusion: Back To The Future
Coronary heart disease has become a leading cause of adult death and results in significant cardiovascular morbidity (1) not only in Europe but worldwide (2). It affects an estimated 1.72% of the human population, resulting in 126 million patients globally (3) who, if not treated, will suffer serious health complications, with myocardial infarction and ischemic cardiomyopathy among them. Coronary Computed Tomography Angiography (CCTA) became an important imaging diagnostic tool in both acute and chronic coronary syndromes for excluding epicardial obstructive coronary artery disease (CAD) and triaging further functional ischemic testing or invasive workup. The latest European Society of Cardiology (ESC) guidelines (4) recommend initial non-invasive imaging (CCTA or ischemic functional testing) in all patients suspected of chronic coronary syndrome. The imaging modality to be used can be selected based on pre-test probability and availability of local expertise and modality capacity (4). CCTA is an excellent modality to exclude obstructive CAD in low and intermediate pre-test probability cases (5, 6). Nevertheless, CCTA can be challenging in high-risk patients with severe calcifications or high Agatston scores since it does not provide any information on myocardial blood flow.
Moreover, in patients with coronary stents, beam hardening artifacts can hamper diagnostic assessment. These challenging scenarios decrease the specificity of CCTA and require additional ischemic functional testing or invasive workup with functional assessment (e.g., invasive fractional flow reserve, (FFR), and instantaneous wave-free ratio (iFR)). The method for determining stenosis severity, grading, and evaluation of CCTA is based mainly on SCCT 2021 Expert Consensus Document on Coronary Computed Tomographic Angiography (7).
On the other hand, several types of stress tests (exercise or pharmacological) may be used clinically to evaluate coronary heart disease. Their applicability varies with patient population, availability, diagnostic accuracy, and cost, starting from simple exercise ECG testing (which is slowly becoming obsolete) to catheter-based invasive coronary angiography. However, some non-invasive imaging modalities may be used to visualize myocardial blood flow changes during a pharmacologicallyinduced stress test. For this, different modalities used are echocardiography, magnetic resonance imaging (MRI), positron emission tomography (PET) CT, single-photon emission computerized tomography (SPECT), dual energy CT (DECT), and dynamic myocardial CT perfusion (CTP). Dynamic CTP is a relatively novel imaging technique that, may be an asset to CCTA examination, particularly in challenging patients as these mentioned above. CTP provides a functional assessment of the myocardial blood flow and, in combination with CCTA, a simultaneous assessment of coronary plaque stenoses (8, 9), resulting in the comprehensive evaluation of the whole heart.
This thesis describes several aspects necessary to understand the complexity of dynamic CTP of the heart, including acquisition, reconstruction, and post-processing methods, image quality, feasibility of dose reduction and diagnostic performance of dynamic CTP stress imaging.