CT Myocardial Perfusion Imaging: A New Frontier in Cardiac Imaging

Abstract

The past two decades have witnessed rapid and remarkable technical improvement of multidetector computed tomography (CT) in both image quality and diagnostic accuracy. These improvements include higher temporal resolution, high-definition and wider detectors, the introduction of dual-source and dual-energy scanners, and advanced postprocessing. Current new generation multidetector row (≥64 slices) CT systems allow an accurate and reliable assessment of both coronary epicardial stenosis and myocardial CT perfusion (CTP) imaging at rest and during pharmacologic stress in the same examination. This novel application makes CT the unique noninvasive "one-stop-shop" method for a comprehensive assessment of both anatomical coronary atherosclerosis and its physiological consequences. Myocardial CTP imaging can be performed with different approaches such as static arterial first-pass imaging, and dynamic CTP imaging, with their own advantages and disadvantages. Static CTP can be performed using single-energy or dual-energy CT, employing qualitative or semiquantitative analysis. In addition, dynamic CTP can obtain quantitative data of myocardial blood flow and coronary flow reserve. The purpose of this review was to summarize all available evidence about the emerging role of myocardial CTP to identify ischemia-associated lesions, focusing on technical considerations, clinical applications, strengths, limitations, and the more promising future fields of interest in the broad spectra of ischemic heart disease.

Figure 1

Static single-energy CTP imaging. 61-year-old male patient with multiple cardiovascular risk factors (smoke, hypercholesterolemia, and hypertension) presented with recurrent atypical chest pain. (a) Coronary CT angiography curved multiplanar reconstruction of the right coronary artery (RCA) with the corresponding orthogonal views showed a critical stenosis (>70% luminal narrowing) at the proximal segment sustained by a large noncalcified atherosclerotic plaque with positive remodeling (arrows). (b) Three-dimensional volume-rendering reconstruction demonstrating the critical stenosis of the proximal RCA (arrowhead) and showing also a tight stenosis (>90%, arrow) of the main diagonal branch (arrow). (c) 17-segment polar plot display of CT perfusion data acquired with a prospectively ECG-triggered high-pitch spiral technique at stress during the first pass, arterial phase, showed large, and severe perfusion defect color-coded in violet/blue/green at the inferior and inferolateral wall; note also a severe area of hypoperfusion in the apical lateral segment and in the apex. (d) Three-dimensional volume-rendering modeling of the left ventricular myocardial perfusion data with superimposed coronary tree (inferior view) showed the critical stenosis of the proximal segment of RCA (arrow) associated with an extensive perfusion defect at the inferior and inferolateral wall extending to apex (color-coded in violet/blue/green).

Figure 2

Static retrospectively ECG gated dual-energy myocardial perfusion imaging. 56-year-old man with multiple cardiovascular risk factors and stable angina. (a) Coronary CT angiography curved multiplanar reconstruction of the left anterior descending artery (LAD) with the corresponding perpendicular views showed a critical stenosis (>70% luminal narrowing) at the proximal segment (arrows) sustained by a large concentric predominately noncalcified plaque with positive remodeling (Remodeling Index= 2.1). (b) The corresponding three-dimensional volume-rendering reconstruction demonstrating the critical stenosis of the proximal LAD (arrow). (c-d) Myocardial short-axis (c) and 2-chamber long-axis (d) color-coded iodine distribution maps of dual-energy CTP imaging during stress showed perfusion defects at the antero-septal, anterior, and antero-lateral wall corresponding to the territory of the left anterior descending artery (arrowheads). Quantitative analysis of the dual-energy map at the level of the anterior wall shows a 71.6% reduction in iodine content (Iodine Density: −0.7 mg/ml) with respect to the remote myocardium at the inferior wall.

Figure 3

Dynamic CTP imaging. 67-year-old obese female patient with history of hyperlipidemia and smoking with suspected coronary artery disease. (a) Curved multiplanar reformation of coronary CT angiography data showed eccentric noncalcified plaque of the main obtuse marginal branch (OM) causing focal critical stenosis (>70% luminal narrowing), arrow. (b) Three-dimensional volume-rendering reconstruction confirmed the severe coronary artery stenosis of the OM (arrow). (c) Three-dimensional color-coded 4-chamber CT perfusion map image derived from the time-resolved dynamic acquisition during stress with the shuttle mode shows extensive perfusion defects in the territory of the OM (basal-middle lateral wall), color-coded in blue, arrowheads. The colors of the myocardium are coded according to the flow values with red, green, and yellow representing higher flow values than blue. The corresponding value of the hemodynamic parameters derived from the time-attenuation curves (TACs) demonstrates a significant reduction of myocardial blood flow in the territory of the OM, consistent with inducible ischemia. Absolute myocardial blood flow was 61.6 mL/100 mL/min and 118.2 mL/100 mL/min in the OM and remote myocardium (septal wall) territories, respectively.