Simplified schematic diagram indicating how extracellular matrix expansion increases the extracellular volume fraction (ECV) with accumulation of Gd contrast in the myocardial extracellular matrix relative to the plasma. Erythrocytes, plasma, myocytes, myocardial capillaries, collagen and extracellular matrix, and molecules of gadolinium (Gd) contrast are shown. The top panels are analogous to the individual from Figure 1 with a low ECV, and the lower panels are analogous to the individual from Figure 2 with a high ECV. Computational steps are also defined.