Fieremans Els, De Deene Yves, Delputte Steven, Ozdemir Mahir S, D'Asseler Yves, Vlassenbroeck Jelle, Deblaere Karel, Achten Eric, Lemahieu Ignace
Department of Electronics and Information Systems, MEDISIP, Ghent University-IBBT-IBiTech, De Pintelaan 185, Ghent, Belgium.
J Magn Reson. 2008 Feb;190(2):189-99. doi: 10.1016/j.jmr.2007.10.014. Epub 2007 Nov 1.
Diffusion weighted magnetic resonance imaging enables the visualization of fibrous tissues such as brain white matter. The validation of this non-invasive technique requires phantoms with a well-known structure and diffusion behavior. This paper presents anisotropic diffusion phantoms consisting of parallel fibers. The diffusion properties of the fiber phantoms are measured using diffusion weighted magnetic resonance imaging and bulk NMR measurements. To enable quantitative evaluation of the measurements, the diffusion in the interstitial space between fibers is modeled using Monte Carlo simulations of random walkers. The time-dependent apparent diffusion coefficient and kurtosis, quantifying the deviation from a Gaussian diffusion profile, are simulated in 3D geometries of parallel fibers with varying packing geometries and packing densities. The simulated diffusion coefficients are compared to the theory of diffusion in porous media, showing a good agreement. Based on the correspondence between simulations and experimental measurements, the fiber phantoms are shown to be useful for the quantitative validation of diffusion imaging on clinical MRI-scanners.
扩散加权磁共振成像能够实现对诸如脑白质等纤维组织的可视化。这种非侵入性技术的验证需要具有已知结构和扩散行为的模体。本文介绍了由平行纤维组成的各向异性扩散模体。使用扩散加权磁共振成像和体核磁共振测量来测量纤维模体的扩散特性。为了能够对测量进行定量评估，使用随机游走者的蒙特卡罗模拟对纤维间间隙空间中的扩散进行建模。在具有不同堆积几何形状和堆积密度的平行纤维的三维几何结构中，模拟了随时间变化的表观扩散系数和峰度，峰度量化了与高斯扩散分布的偏差。将模拟的扩散系数与多孔介质中的扩散理论进行比较，显示出良好的一致性。基于模拟与实验测量之间的对应关系，表明纤维模体可用于临床MRI扫描仪上扩散成像的定量验证。
