Vymazal J, Hajek M, Patronas N, Giedd J N, Bulte J W, Baumgarner C, Tran V, Brooks R A
Neuroimaging Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
J Magn Reson Imaging. 1995 Sep-Oct;5(5):554-60. doi: 10.1002/jmri.1880050514.
A retrospective analysis of 158 T1-weighted and T2-weighted MRI scans of normal brains at 0.5 and 1.5 Tesla was performed. Signal intensities in the frontal cortex, caudate nucleus, putamen, and globus pallidus were divided by those of frontal white matter; and these gray/white ratios were correlated with iron concentration, estimated from the anatomical region and age of the patient. Intraregional plots were also made of gray/white ratio versus age for the 1.5 Tesla scans. The changes in both T1-weighted and T2-weighted ratios were consistent with the hypothesis that 1/T1 and 1/T2 vary linearly with iron concentration, and the corresponding coefficients, determined separately from the interregional and intraregional plots, were generally in agreement. Furthermore, the variability of the MRI ratios at 1.5 Tesla was consistent with expected iron variability except for the cortex, in which partial volume errors due to sulci and white matter caused increased variations. The MRI results agreed well with in vitro data on T1 and T2 in tissue specimens and with other MRI studies. When compared with T1 and T2 in ferritin solution, a significant "tissue relaxation enhancement" was found, attributable to slower diffusion and clustering of ferritin in tissue.
对158例在0.5和1.5特斯拉下进行的正常脑T1加权和T2加权MRI扫描进行了回顾性分析。将额叶皮质、尾状核、壳核和苍白球的信号强度除以额叶白质的信号强度；这些灰/白比值与根据患者的解剖区域和年龄估算的铁浓度相关。还针对1.5特斯拉扫描绘制了灰/白比值与年龄的区域内图表。T1加权和T2加权比值的变化与1/T1和1/T2随铁浓度呈线性变化的假设一致，并且分别从区域间和区域内图表确定的相应系数总体上相符。此外，1.5特斯拉下MRI比值的变异性与预期的铁变异性一致，但皮质除外，在皮质中，由于脑沟和白质导致的部分容积误差引起了更大的变异性。MRI结果与组织标本中T1和T2的体外数据以及其他MRI研究结果非常吻合。与铁蛋白溶液中的T1和T2相比，发现了显著的“组织弛豫增强”，这归因于铁蛋白在组织中的扩散较慢和聚集。
