Assessment of coronary blood flow with computed tomography and magnetic resonance imaging

Abstract

Noninvasive assessment of myocardial blood flow (MBF) has proved to be useful for the diagnosis and risk stratification of patients with known or suspected coronary artery disease. However, the relationship between myocardial perfusion abnormalities and coronary atherosclerosis is complex, and one is not necessarily predictive of the other. 1,2 An example of this is in diminished MBF, which can also be caused by microvascular dysfunction without correlation to flow-limiting epicardial lesions. 3 In contrast to this, normal MBF can persist despite severe coronary disease due to the presence of collateral blood flow. Coronary angiography and myocardial perfusion imaging has become complementary, rather than substitutive methods to evaluate coronary artery disease. 4 Single-photon emission computed tomography (SPECT) represents the most widely applied methods for myocardial perfusion assessment in clinical practice today, while positron emission tomography (PET) is the most reliable method for noninvasive absolute MBF quantification. In recent years, cardiac magnetic resonance (MR) and cardiac computed tomography (CT) have emerged as promising techniques for MBF assessment. In these tomographic imaging techniques, measurement of MBF is based upon tissue enhancement of an intravenous delivered contrast bolus. Both imaging modalities provide high spatial and temporal resolution to determine regional MBF, and allow complementary measurements of cardiac function, structure, and coronary architecture. In this review, we will explore the basic principles of cardiac MR and CT perfusion imaging methods, with a special emphasis on recent emerging methods that allow for combined coronary artery and MBF measurement by CT.