Relaxation rates of protons in gadolinium chelates detected with a high-Tc superconducting quantum interference device in microtesla magnetic fields

A nuclear magnetic resonance and imaging system was constructed to study spin-lattice relaxation time T-1, spin-spin relaxation time T-2, and effective relaxation time T-2* of gadolinium (Gd) chelates using a high-T-c superconducting quantum interference device in microtesla magnetic fields. In the presence of the magnetic contrast T-2* is related to T-2 by the relation: 1/T-2*=1/T-2+gamma Delta B+Gamma(Gd-chelates), where gamma=42.58 kHz/mT and gamma Delta B is the relaxation rate due to the inhomogeneity field Delta B in measuring coil at the sample position and Gamma(Gd-chelates) is the intrinsic relaxation rate of Gd chelates. It is found that T-1, T-2, and 1/Gamma(Gd-chelates) decay exponentially as the concentration (or magnetic susceptibility) of Gd chelates increases. The Gd chelates cause a diffusive motion of nuclear spins and hence enhance the relaxation rates. Enhanced image contrast has been demonstrated in a water phantom with Gd chelates in microtesla magnetic fields. (C) 2010 American Institute of Physics. [doi:10.1063/1.3493737]