In vivo lipid diffusion coefficient measurements in rat bone marrow
In vivo lipid diffusion coefficient measurements in rat bone marrow
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DOI：
10.1016/j.mri.2008.11.004
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发表时间：
2009-07-01
影响因子：
2.5
通讯作者：
Mulkern, Robert V.
中科院分区：
文献类型：
--
作者：
Ababneh, Zaid Q.;Beloeil, Helene;Mulkern, Robert V.
脂质在骨髓、脂肪沉积物和体内代谢活性细胞内脂质内的扩散系数D（I）将取决于几个因素，包括脂质分布的精确化学组成（链长、不饱和度等）。以及温度。因此，D（1）最终可以证明在评估与诸如囊性纤维化、糖尿病和冠心病的疾病相关的异常脂肪酸分布中的价值。D（I）的敏感温度依赖性也可以证明对于用于骨肿瘤或其他脂肪组织（如乳房）内的疾病的MR引导的热疗法的价值。然而，由于多种原因，在体内测量高分子量脂质的扩散系数在技术上是困难的。例如，由于与水相比低得多的扩散系数，需要比用于中枢神经系统应用的那些高得多的B因子。此外，脉冲序列设计必须尽可能地包含对运动、敏感性和化学位移效应的免疫力，无论何时进行身体成像。在这项工作中，高b因子线扫描扩散成像序列的设计，实施和测试的D（1）测量使用4.7-T水平孔动物扫描仪。可用的梯度设置允许B因子高达0.03 μ s/nm（2）（30，000 s/mm（2）），回波时间短至42 ms。该方法用于测量体内大鼠爪骨髓内的脂质扩散系数，产生的脂质扩散系数比典型组织水扩散系数小约两个数量级。还进行了证明脂质扩散系数对链长和温度的敏感性的体模实验。(C)2009 Elsevier Inc. All rights reserved.
The diffusion coefficient of lipids, D(l), within bone marrow, fat deposits and metabolically active intracellular lipids in vivo will depend on several factors including the precise chemical composition of the lipid distribution (chain lengths, degree of unsaturation, etc.) as well as the temperature. As such, D(l) may ultimately prove of value in assessing abnormal fatty acid distributions linked to diseases such as cystic fibrosis, diabetes and coronary heart disease. A sensitive temperature dependence of D(l) may also prove of value for MR-guided thermal therapies for bone tumors or disease within other fatty tissues like the breast. Measuring diffusion coefficients of high molecular weight lipids in vivo is, however, technically difficult for a number of reasons. For instance, due to the much lower diffusion coefficients compared to water, much higher b factors than those used for central nervous system applications are needed. In addition, the pulse sequence design must incorporate, as much as possible, immunity to motion, susceptibility and chemical shift effects present whenever body imaging is performed. In this work, high b-factor line scan diffusion imaging sequences were designed, implemented and tested for D(l) measurement using a 4.7-T horizontal bore animal scanner. The gradient set available allowed for b factors as high as 0.03 mu s/nm(2) (30,000 s/mm(2)) at echo times as short as 42 ms. The methods were used to measure lipid diffusion coefficients within the marrow of rat paws in vivo, yielding lipid diffusion coefficients approximately two orders of magnitude smaller than typical tissue water diffusion coefficients. Phantom experiments that demonstrate the sensitivity of lipid diffusion coefficients to chain length and temperature were also performed. (C) 2009 Elsevier Inc. All rights reserved.