Influence of Mn(II) on NMR relaxation times of biological fluids

The extent that various concentrations of the paramagnetic metal ion manganese [Mn(II)] affect nuclear magnetic resonance (NMR) relaxation times was studied in vitro. Serial dilutions of Mn(II) were prepared in distilled water, 4% human serum albumin, dog plasma, dog gallbladder bile, and dog hepatic bile. T1 and T2 of each were measured at 10.7 M Hz using magnetization recovery and spin-echo radiofrequency sequences, respectively. The results show that relaxation rates (1/T1 and 1/T2) increase in a linear manner with increasing concentration of Mn(II) in all of the solutions tested. Mn(II) dissolved in dog gallbladder and hepatic bile, dog plasma, and 4% human serum albumin reduced relaxation times to a greater extent than Mn(II) in water. T1 times were reduced to a greater extent than T2 values. Thus, in T1 weighted magnetic resonance images, the NMR signal used to produce images would be more sensitive to the presence of Mn(II) in these biological fluids than in water. Furthermore, the magnitude of this in vivo effect of Mn(II) on NMR relaxation parameters depends not only on the concentration of this paramagnetic ion, but also on the constituents comprising the biological fluids (intra- and extracellular water, bile, plasma) and the nature of the chemical molecular interactions between these constituents and Mn(II).