Utility Decay Rates of T₁-Weighted Magnetic Resonance Imaging Contrast Based on Redox-Sensitive Paramagnetic Nitroxyl Contrast Agents

抄録

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.