ASSESSMENT OF RELATIVE BRAIN IRON CONCENTRATIONS USING T-2-WEIGHTED AND T-2(ASTERISK)-WEIGHTED MRI AT 3-TESLA

In this paper a new method is presented for the relative assessment of brain iron concentrations based on the evaluation of T-2 and T-2*-weighted images. A multiecho sequence is employed for rapid measurement of T-2 and T-2*, enabling calculation of the line broadening effect (T-2'). Several groups have failed to show a correlation between T,and brain iron content. However, quantification of T-2', and the associated relaxation rate R(2)', may provide a more specific relative measure of brain iron concentration. This may find application in the study of brain diseases, which cause associated changes in brain iron levels. A new method of field inhomogeneity correction is presented that allows the separation of global and local field inhomogeneities, leading to more accurate T-2* measurements and hence, T-2' values. The combination of T-2*, and T-2-weighted MRI methods enables the differentiation of Parkinson's disease patients from normal age-matched controls based on differences in iron content within the substantia nigra.