Relation between Blood and Cardiac Manganese during Manganese Enhanced Magnetic Resonance Imaging (MEMRI) with T1 Mapping in the Rodent

摘要

The Manganese ion (Mn²⁺) enters viable myocardial cells via voltage gated calcium channels. Because of its shortening of T1 and its relatively long half-life in cells, Mn²⁺ can serve as an intracellular, molecular contrast agent to study calcium influx in the myocardium. One major concern for using Mn²⁺ is its sensitivity over a limited range of concentrations using T1-weighted images for visualization, which limits its potential in quantitative techniques. Therefore, in this study, a T1 mapping method has been implemented for cardiac manganese-enhanced MRI (MEMRI) to enable a quantitative estimate of influx over a wide range of concentrations. This method was used to compare the relation between T1 changes in the heart as a function of cardiac and blood Mn²⁺ levels. We observed a non-linear relationship between the blood Mn²⁺ infused and LV wall ΔR1. At low levels of blood Mn²⁺ there was less cardiac enhancement than at higher levels of blood Mn²⁺. However both myocardium and blood level of Mn²⁺ were not linearly proportional to the total Mn²⁺ infused, most likely due to liver or kidney clearance.