摘要：The availability and applicability of the combination of paramagnetic nitroxyl contrast agent and T1-weighted gradient echo (GE)-based dynamic magnetic resonance imaging (MRI) measurement for redox imaging are described. The time courses of T1-weighted GE MRI signal intensities according to first-order paramagnetic loss of a nitroxyl contrast agent were simulated for several experimental conditions. The apparent decay rate calculated based on decreasing T1-weighted MRI contrast ( k MRI) can show an approximate value of the original decay rate ( k true) discretionarily given for simulation with suitable experimental parameters. The difference between k MRI and k true can be sufficiently small under T1-weighted spoiled gradient echo (SPGR) scan conditions (repetition time=75 ms, echo time=3 ms, and flip angle=45°), with a conventional redox-sensitive nitroxyl contrast agent, such as 4-hydroxy-2,2,6,6,-tetramethylpiperidine- N -oxyl (TEMPOL) and/or 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine- N -oxyl (carbamoyl-PROXYL), and with i.v. doses of below 1.5 μmol/g b.w. for mice. The results of this simulation suggest that the k MRI of nitroxyl contrast agents can be the primary index of redox status under biological conditions.
