Rapid calculations of susceptibility-induced magnetostatic field perturbations for in vivo magnetic resonance
Rapid calculations of susceptibility-induced magnetostatic field perturbations for in vivo magnetic resonance
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DOI：
10.1088/0031-9155/51/24/007
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发表时间：
2006-12-21
影响因子：
3.5
通讯作者：
de Graaf, Robin A.
中科院分区：
文献类型：
--
作者：
Koch, Kevin M.;Papademetris, Xenophon;de Graaf, Robin A.
由样品内磁化率的变化产生的静磁场扰动降低了磁共振测量的质量和完整性。这些扰动很难在体内预测，因为体内内部磁化率分布的变化很大。最近的发展提供了快速的计算手段，估计静态场的不均匀性内的小磁化率限制的材料，通常使用磁共振研究。这种预测机制可以是序列模拟、场匀场和采集后图像校正的有价值的工具。在这里，我们探讨这种计算协议，并证明其预测能力，估计在人体大脑内的体内不均匀性。此外，我们定量地探讨了计算的预测极限。在体内比较，使用MRI和CT数据的磁化率注册的方法，并利用进行特定主题的不均匀性估计。使用该算法，直接比较在人脑和幻影之间的字段地图采集和计算的不均匀性。由于静态场的不均匀性在回波平面图像中的失真校正也证明了使用计算的场图。
Static magnetic field perturbations generated by variations of magnetic susceptibility within samples reduce the quality and integrity of magnetic resonance measurements. These perturbations are difficult to predict in vivo where wide variations of internal magnetic susceptibility distributions are common. Recent developments have provided rapid computational means of estimating static field inhomogeneity within the small susceptibility limits of materials typically studied using magnetic resonance. Such a predictive mechanism could be a valuable tool for sequence simulation, field shimming and post-acquisition image correction. Here, we explore this calculation protocol and demonstrate its predictive power in estimating in vivo inhomogeneity within the human brain. Furthermore, we quantitatively explore the predictive limits of the computation. For in vivo comparison, a method of magnetic susceptibility registration using MRI and CT data is presented and utilized to carry out subject-specific inhomogeneity estimation. Using this algorithm, direct comparisons in human brain and phantoms are made between field map acquisitions and calculated inhomogeneity. Distortion correction in echo-planar images due to static field inhomogeneity is also demonstrated using the computed field maps.