Measurement of the intracellular lifetime of water to estimate myocardial cell size is not feasible in humans using clinical contrast agent doses at 1.5T

Background Measurement of the myocardial extracellular volume fraction (ECV) assumes a dynamic equilibrium with rapid exchange of an extracellular contrast agent between myocardium and blood. This equilibrium would be manifested by a linear relationship between 1/T1 (R1) of myocardium and 1/T1* (R1*) of blood. This relationship has been shown to be non-linear for high R1 values in mice, and this has been used to calculate the intracellular lifetime of water and estimate myocardial cell size. We sought to determine whether the relationship between R1 of myocardium and R1* of blood is linear or non-linear in patients scanned under clinical conditions.