[Delayed myocardial enhancement: Optimizing the MR imaging protocol]

The purpose of this article is to 1) review the basic models characterizing myocardial enhancement on MR and CT, 2) review the main characteristics of available iodinated and Gadolinium-based contrast agents and, 3) review the literature on emerging MR contrast agents to assess myocardial viability. The intensity of enhancement following infarction is the result of two processes: 1) the increased interstitial space (15 + or - 2% in normal myocardium and 80 + or - 3% in necrotic tissue) secondary to cell necrosis and 2) perfusion abnormalities secondary to absent revascularization or impaired microvascularization. The equation described by Kety was used to create models of contrast material kinetics within myocardium or enhancement of the different components of the myocardium (viable myocardium, necrosed myocardium, fibrosis, with no-reflow zone, hibernating or stunned myocardium).