This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Elevated levels of brain iron have been implicated in multiple neurological disorders, including Parkinsons and Alzheimers disease. A non-invasive means to measure brain iron would therefore provide a valuable tool to study the role of iron in such brain diseases. In this work, we are investigating the ability of high field MRI to quantify brain iron, using the known effect of paramagnetic atoms (like iron) on the transverse relaxation time, T2. For this purpose, a new pulse sequence was developed to permit precise measurement of T2 values rapidly. In experiments on normal human brain at 4.7 Tesla, T2 values in five different gray matter regions were found to range from 38 +/- 2 ms (globus pallidus) to 64 +/- 2 ms (frontal cortex). The apparent relaxation rate (1/T2) in these five regions showed strong correlation with published levels of iron (Fe) in those regions. The linear coefficient relating 1/T2 and [Fe] at 4.7 T was measured to be 0.551 (s/mg Fe/100 g f.w.)-1. When compared with the values obtained in a previous report for six different static fields (B0) up to 1.5 T, the measurement confirmed the linear dependence of the linear coefficient on B0 up to 4.7 T. These results suggest that the T2 value in the human brain is predominantly affected by the non-heme iron distribution. The strong correlation between the obtained T2 values and the regional iron concentrations suggests a role for high field MRI in quantifying in vivo brain iron.
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