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

摘要

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-Tc 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+γB +Γ_(Gd-chelates),where γ=42.58 kHz/mT and yAB is the relaxation rate due to the inhomogeneity field AB in measuring coil at the sample position and +Γ_(Gd-chelates) is the intrinsic relaxation rate of Gd chelates. It is found that T_1; T_2, and l/Γ_(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.