The correlation between phase shifts in gradient-echo MR images and regional brain iron concentration

The purpose of this study was to investigate the relationship between the m agnetic susceptibility of brain tissue and iron concentration. Phase shifts in gradient-echo images (TE = 60 ms) were measured in 21 human subjects, ( age 0.7-45 years) and compared with published values of regional brain iron concentration. Phase was correlated with brain iron concentration in putam en (R-2 = 0.76), caudate (0.72), motor cortex (0.68), globus pallidus (0.59 ) (all p < 0.001), and frontal cortex (R-2 = 0.19, p = 0.05), but not in wh ite matter (R-2 = 0.05,p 0.34). The slope of the regression (degrees/mg iro n/g tissue wet weight) varied over a narrow range from -1.2 in the globus p allidus and frontal cortex to -2.1 in the caudate, These results suggest th at magnetic resonance phase reflects iron-induced differences in brain tiss ue susceptibility in gray matter. The lack of correlation in white matter m ay reflect important differences between gray and white matter in the cellu lar distribution and the metabolic functions of iron. Magnetic resonance ph ase images provide insight into the magnetic state of brain tissue and may prove to be useful in elucidating the relationship between brain iron and t issue relaxation properties. (C) 1999 Elsevier Science Inc.