MnIIIporphyrin (MnP)holds the promise of addressingthe emerging challenges associated with Gd-based clinical MRI contrastagents (CAs), namely, Gd-related adverse effect and decreasing sensitivityat high clinical magnetic fields. Two complementary strategies fordeveloping new MnPs as Gd-free CAs with optimized biocompatibilitywere established to improve relaxivity or clearance rate. MnPs withdistinct and tunable pharmacokinetic properties can consequently beconstructed for different in vivo applications at clinical field of3 T. [ABSTRACT FROM AUTHOR]