Positron emission tomography: principles and applications in cardiology

Positron emission tomography (PET) is a noninvasive imaging technique of nuclear medicine that permits to delineate the temporal and spatial distribution of PET tracers on tomographic images. When compared to other imaging techniques commonly used in nuclear medicine such as SPECT imaging (Single Photon Emission Tomography), PET offers several advantages: 1. PET isotopes are available for the basic elements of organic chemistry such as nitrogen, carbon, or oxygen, so that physiologic tracer substances can be synthesized to study perfusion and metabolism. 2. The use of coincidence electronics for the detection of radiation leads to electronic collimation and results in high image resolution. 3. Photon attenuation is corrected individually for each patient using transmission images, so that quantitative measurements can be obtained. When compared to other imaging modalities used in cardiology, PET uniquely offers the capability to measure noninvasively and quantitatively regional myocardial perfusion (ml/g/min) and different metabolic processes such as myocardial glucose utilisation (μmol/min/g). Clinical applications of PET include the diagnosis of coronary artery disease and the assessment of myocardial viability after ischemic tissue injury. Particularly for patients with reduced left ventricular function or with regional wall motion abnormalities, PET can be considered the standard method for patient selection and risk stratification with respect to revascularisation procedures. The identification of persistent glucose utilisation in ischemically injured myocardial tissue accurately discerns myocardium with potentially reversible dysfunction from scar tissue with irreversible tissue injury. (authors)