Quantum chemical insight into the effects of the local electron environment on T(2)*-based MRI

T(2)* relaxation is an intrinsic magnetic resonance imaging (MRI) parameter that is sensitive to local magnetic field inhomogeneities created by the deposition of endogenous paramagnetic material (e.g. iron). Recent studies suggest that T(2)* mapping is sensitive to iron oxidation state. In this study, we evaluate the spin state-dependence of T(2)* relaxation using T(2)* mapping. We experimentally tested this physical principle using a series of phantom experiments showing that T(2)* relaxation times are directly proportional to the spin magnetic moment of different transition metals along with their associated magnetic susceptibility. We previously showed that T(2)* relaxation time can detect the oxidation of Fe(2+). In this paper, we demonstrate that T(2)* relaxation times are significantly longer for the diamagnetic, d(10) metal Ga(3+), compared to the paramagnetic, d(5) metal Fe(3+). We also show in a cell culture model that cells supplemented with Ga(3+) (S = 0) have a significantly longer relaxation time compared to cells supplemented with Fe(3+) (S = 5/2). These data support the hypothesis that dipole–dipole interactions between protons and electrons are driven by the strength of the electron spin magnetic moment in the surrounding environment giving rise to T(2)* relaxation.