Estimation of brain iron in vivo by means of the interecho time dependence of image contrast

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Abstract
An imaging protocol for a quantitative estimation of disease-induced variations in brain iron is proposed and then validated, first, on a phantom and second, on a group of 11 healthy volunteers. The relative estimate of brain iron is achieved from a rate difference image that measures the enhancement, δR2app, of the transverse relaxation rate of water protons brought about by the heterogeneous accumulation of iron in the glial cells. At 1.5 T, the phantom study demonstrates, over the range 0-6 A/m, a linear dependence of δR2app on the magnetization difference between micro-spheres and a paramagnetic gel, with a sensitivity of ∼2 s−1 A−1 m. In the group of healthy volunteers (mean age 33 ± 7 years) devoid of disease-related or appreciable age-related accumulations of iron, the precision of δR2app was still sufficient to distinguish the globus pallidus and the putamen from all of the other iron-containing brain structures in a manner that was significant at the 99% confidence level.