The many ways to myocardial perfusion imaging.

Myocardial perfusion imaging (MPI) is important for the management of patients with suspected or known coronary artery disease (CAD). Nuclear cardiology is the most widely used noninvasive approach for the assessment of myocardial perfusion. The available single-photon emission computed tomography (SPECT) flow agents are characterized by a rapid myocardial extraction and by a cardiac uptake proportional to blood flow. In addition, different positron emission tomography (PET) tracers may be used for the quantitative measurement of myocardial blood flow and coronary flow reserve. The decrease in blood flow, determined by coronary artery stenosis, produces myocardial ischemia leading to perfusion abnormalities detectable by SPECT or PET in the early phase of ischemia. Other imaging techniques, such as contrast echocardiography and magnetic resonance imaging (MRI) have been more recently proposed as alternative methods for the evaluation of myocardial perfusion. Although several technical aspects have to be better defined to use contrast echocardiography in clinical practice, this approach appears promising for the evaluation of myocardial perfusion. MRI has also been proposed for the assessment of myocardial perfusion by measuring the alteration of regional myocardial magnetic properties after the intravenous injection of contrast agents. Due to the high contrast and spatial resolution of the technique, MRI allows differentiating sub-endocardial and sub-epicardial perfusion, emerging as a potential alternative non-ionizing technique to evaluate myocardial perfusion. This review illustrates the noninvasive imaging modalities for the evaluation of myocardial perfusion, underlying advantages and disadvantages of each technique.