Insight into In Vivo Magnetization Exchange in Human White Matter Regions
Insight into In Vivo Magnetization Exchange in Human White Matter Regions
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DOI：
10.1002/mrm.22873
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发表时间：
2011-10-01
影响因子：
3.3
通讯作者：
MacKay, Alex L.
中科院分区：
文献类型：
--
作者：
Kalantari, Saeed;Laule, Cornelia;MacKay, Alex L.
水交换可以在解释脑中特定分区的磁共振成像数据中发挥重要作用。例如，髓磷脂测量的MR方法（称为髓磷脂水分数成像）假设水交换过程与测量时间尺度相比是缓慢的。在这篇文章中，我们研究了水交换过程是否对髓鞘水分数值有影响。先前建立的白色物质的四池模型用于模拟两个水性隔室（髓磷脂水和内/胞外水）和非水性隔室（髓磷脂和非髓磷脂组织）之间的相互作用。为了提取水交换交叉弛豫时间，解析求解Bloch方程。由于水交换时间尺度取决于这四个池中的每一个的自旋晶格T（1）弛豫，并且由于与每个池相关的T（1）的当前不确定性，计算了三种不同T（1）情景的交换交叉弛豫时间。为了使髓磷脂水分数成为髓磷脂的准确标记物而需要考虑的校正被发现小于15%。这项工作表明，白色物质髓鞘水分数值的区域变化最有可能是由于髓鞘含量的变化，而不是汇率的区域差异。Magn Reson Med 66：1142-1151，2011。(C)2011 Wiley-Liss，Inc.
Water exchange can play an important role in interpreting compartment-specific magnetic resonance imaging data in brain. For example, an MR method of myelin measurement, known as myelin water fraction imaging, assumes that water exchange processes are slow compared with the measurement time scale. In this article, we examined whether water exchange processes have an effect on myelin water fraction values. A previously established four pool model of white matter was used to simulate the interactions between two aqueous compartments (myelin water and intra/extracellular water) and nonaqueous compartments (myelin and nonmyelin tissues). To extract the water exchange cross relaxation times, the Bloch equations were solved analytically. As the water exchange time scales are dependent on the spin-lattice T(1) relaxation of each of these four pools and due to the current uncertainties regarding the T(1) associated with each pool, exchange cross relaxation times for three different T(1) scenarios were calculated. The corrections that need to be considered in order for myelin water fraction to be an accurate marker for myelin were found to be less than 15%. This work indicates that regional variations in white matter myelin water fraction values are most likely due to variations in myelin content rather than regional differences in exchange rates. Magn Reson Med 66:1142-1151, 2011. (C) 2011 Wiley-Liss, Inc.