Evaluation of Brain Iron Content Based on Magnetic Resonance Imaging (MRI): Comparison among Phase Value, R2* and Magnitude Signal Intensity

BACKGROUND AND PURPOSE Several magnetic resonance imaging (MRI) techniques are being exploited to measure brain iron levels increasingly as iron deposition has been implicated in some neurodegenerative diseases. However, there remains no unified evaluation of these methods as postmortem measurement isn't commonly available as the reference standard. The purpose of this study was to make a comparison among these methods and try to find a new index of brain iron. METHODS We measured both phase values and R2* in twenty-four adults, and performed correlation analysis among the two methods and the previously published iron concentrations. We also proposed a new method using magnitude signal intensity and compared it with R2* and brain iron. RESULTS We found phase value correlated with R2* in substantia nigra (r = -0.723, p<0.001) and putamen (r = -0.514, p = 0.010), while no correlations in red nucleus (r = -0.236, p = 0.268) and globus pallidus (r = -0.111, p = 0.605). And the new magnitude method had significant correlations in red nucleus (r = -0.593, p = 0.002), substantia nigra (r = -0.521, p = 0.009), globus pallidus (r = -0.750, p<0.001) and putamen (r = -0.547, p = 0.006) with R2*. A strong inverse correlation was also found between the new magnitude method and previously published iron concentrations in seven brain regions (r = -0.982, P<0.001). CONCLUSIONS Our study indicates that phase value may not be used for assessing the iron content in some brain regions especially globus pallidus. The new magnitude method is highly consistent with R2* especially in globus pallidus, and we assume that this approach may be acceptable as an index of iron content in iron-rich brain regions.