In and ex vivo MR evaluation of acute myocardial ischemia in pigs by determining R1 in steady state after the administration of the intravascular contrast agent NC100150 injection

Rationale and Objectives: To study the dose response in perfused and nonperfused myocardium by measuring relaxation rate (RI) in a steady-state situation after injection of the intravascular contrast agent NC100150 Injection in pigs and whether the dose response differs in vivo and ex vivo. Materials and Methods: The left anterior descending artery was occluded. R1 was measured using a Look-Locker sequence for 2 dose groups (2 mg Fe/kg bw, n = 4, and 5 mg Fe/kg bw, n = 5) and a control group (n = 3). Results: A significant increase in R1 was found in perfused myocardium after contrast agent injection, in contrast to nonperfused myocardium. There was a significantly larger difference in R1 between perfused and nonperfused myocardium in the 5 mg Fe/kg bw dose group compared with the other 2 groups. The difference in R1 between perfused and nonperfused myocardium was significantly higher in vivo than ex vivo. Conclusion: A nearly linear R1 dose response was found in perfused myocardium in vivo. The dose response ex vivo was less steep possibly due to larger water exchange limitations.