Combined Positron Emission Tomography and Magnetic Resonance as Translational Tool in Cardiology.

In this issue of Circulation: Cardiovascular Imaging, Bulluck et al introduce simultaneous positron emission tomography and magnetic resonance (PET-MR) imaging as a sophisticated research tool to correlate cardiac function, area of risk, metabolism, and infarct size in patients with acute myocardial infarction. Imaging is increasingly applied for the noninvasive characterization of acute and chronic ischemic injury. Impaired perfusion and wall motion are considered to be diagnostic hallmarks of ischemic injury. Therefore, myocardial perfusion imaging and echocardiography are commonly used to identify location, extent, and severity of ischemic injury. With the advent of cross-sectional imaging, such as single photon emission tomography (SPECT), PET, and MR, more sophisticated means have become available for tomographic visualization of myocardial ischemia and its consequences. At the same time, new tracer techniques have been introduced to provide molecular signals beyond myocardial perfusion. Thallium-201 imaging was the first technology to be applied for the differentiation between reversible perfusion abnormalities as a marker of viable myocardium and persistent defects associated with scar formation, but this imaging approach is only rarely used anymore because of high radiation exposure. With the introduction of PET in the 1980s, metabolic characterization of regional ischemic injury became possible. Using tracers such as C-11 palmitate, C-11 acetate, and FDG, acute metabolic effects of ischemia have been documented.