Evaluation of manganese -trans-1,2-diaminocyclohexane-N,N,N′, N′-tetraacetate complex (Cyclomang) as paramagnetic contrast agent for magnetic resonance imaging

Preclinical evaluation of a 0.5 M solution of the manganese(II) - trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetate complex (Mn-DCTA, Cyclomang) has been carried out with a view to substitution of potentially toxic gadolinium-containing paramagnetic contrast agents for clinical MRI routines. The toxicological tests of Mn(II)-DCTA were performed on mice and rats. Liquid phantoms were used for evaluating the relaxivity of Mn(II)-DCTA in comparison to that of Gd(III)-DTPA and Mn-DTPA. The diagnostic imaging properties of Mn(II)-DCTA were quantitatively assessed on dogs with cerebral meningeomas (n = 10). The LD₅₀ upon single administration in rats was above 17 ml/kg, thus slightly exceeding the corresponding values for of Gd(III)-DTPA and Mn-DTPA. The relaxivity of Mn(II)-DCTA amounted to R1 =3.68 (mM^-1 · s^-1) and did not differ significantly from the values known for Gd-DTPA and Mn-DTPA. Mn(II)-DCTA ensured high-intensity contrast of tumor areas in brain of dogs. It is concluded that Mn(II)-DCTA can be employed as a paramagnetic contrast agent in routine MRI studies and is worth further clinical evaluation.