Signal decay due to susceptibility-induced intravoxel dephasing on multiple air-filled cylinders: MRI simulations and experiments
Signal decay due to susceptibility-induced intravoxel dephasing on multiple air-filled cylinders: MRI simulations and experiments
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DOI：
10.1007/s10334-008-0119-1
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发表时间：
2008-08-01
影响因子：
2.3
通讯作者：
Davenel, Armel
中科院分区：
文献类型：
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作者：
De Guio, Francois;Benoit-Cattin, Hugues;Davenel, Armel
目的表征磁化率伪影，评估嵌入水中的充气圆柱体的回波时间、像素大小和物体几何形状的梯度回波信号衰减函数。材料和方法在小型相互作用的充气圆柱体网络上使用 0.2 T 磁铁进行实验，并结合体素内的磁共振成像 (MRI) 模拟 失相。在真实和模拟图像的不同像素大小下评估回波时间上的信号衰减。通过仿真研究了半径、圆柱体之间的距离和主磁场的影响。结果随着回波时间或像素尺寸的增加，信号损失更大。体素信号衰减不是指数衰减，而是通过集成回波时间、像素大小和场不均匀性的窦基数函数进行加权，这取决于主磁场强度和物体的几何配置。仿真能够模拟信号衰减，即使对于由多个圆柱体组成的复杂物体也是如此。因此，我们观察到的具体实验信号调制可以通过模拟重现和解释。 结论 0.2 T 的定量信号衰减方法可用于局部规则空气/水界面情况下的表征研究，因为信号取决于相对于像素大小的物体大小，并且与几何配置相关。此外，模拟和实验之间的良好一致性应该导致对磁化率与其他物体（例如球体网络）的影响的进一步研究。因此，MRI 模拟是分子和多孔介质成像的潜在工具。
Objective Characterization of magnetic susceptibility artefacts with assessment of the gradient-echo signal decay function of echo time, pixel size, and object geometry in the case of air-filled cylinders embedded in water.Materials and methods Experiments were performed with a 0.2 T magnet on a network of small interacting air-filled cylinders along with Magnetic resonance imaging (MRI) simulations integrating intravoxel dephasing. Signal decay over echo time was assessed at different pixel sizes on real and simulated images. The effects of radius, distance between cylinders and main magnetic field were studied using simulation.Results Signal loss was greater as echo time or pixel size increased. Voxel signal decay was not exponential but was weighted by sinus cardinalis functions integrating echo time, pixel size and field inhomogeneities which depended on main magnetic field strength and geometric configuration of the object. Simulation was able to model signal decay, even for a complex object constituted of several cylinders. The specific experimental signal modulation we observed was thus reproduced and explained by simulation.Conclusion The quantitative signal decay approach at 0.2 T can be used in characterization studies in the case of locally regular air/water interfaces as the signal depends on object size relative to pixel size and is relevant to the geometric configuration. Moreover, the good concordance between simulation and experiments should lead to further studies of magnetic susceptibility effects with other objects such as networks of spheres. MRI simulation is thus a potential tool for molecular and porous media imaging.