Magnetic Resonance-Electrical Properties Tomography by Directly Solving Maxwell's Curl Equations
Magnetic Resonance-Electrical Properties Tomography by Directly Solving Maxwell's Curl Equations
复制标题
直接求解麦克斯韦旋度方程的磁共振-电特性层析成像
DOI：
10.3390/app10093318
复制
发表时间：
2020-05-01
影响因子：
2.7
通讯作者：
Liu, Feng
中科院分区：
文献类型：
--
作者：
Chi, Jieru;Guo, Lei;Liu, Feng
磁共振-电学特性层析成像(MR-EPT)是一种在磁共振成像(MRI)中根据测量的射频(RF)场重建生物组织电特性(EPs)的方法。目前的MR-EPT方法是通过求解二阶偏微分波方程来重建EP轮廓的，该问题对噪声敏感，会在组织边界附近和视野测量不准确的区域产生大量重建伪影。本文提出了一种基于直接求解麦克斯韦旋度方程的MR-EPT方法。利用时域有限差分法(FDTD)计算出的射频场与实测值进行迭代拟合，得到EPs的分布。为了解决迭代拟合耗时的问题，采用图形处理器(GPU)加速FDTD技术对场计算内核进行处理。通过对一个数值头部模型的研究，对新的EPT方法进行了评估，发现EP值可以准确地计算出来，并且对模拟的射频场误差相对不敏感。使用从9.4特斯拉(T)磁共振成像(MRI)系统收集的基于体模的实验数据进一步验证了所提出方法的可行性。结果还表明，与传统方法相比，新方法可以重建出更准确的EP值。此外，即使在没有射频场的相位信息的情况下，所提出的方法仍然能够提供健壮的EPT解决方案，从而提高了潜在的临床应用的实用性。
Magnetic Resonance-Electrical Properties Tomography (MR-EPT) is a method to reconstruct the electrical properties (EPs) of bio-tissues from the measured radiofrequency (RF) field in Magnetic Resonance Imaging (MRI). Current MR-EPT approaches reconstruct the EP profile by solving a second-order partial differential wave equation problem, which is sensitive to noise and can induce large reconstruction artefacts near tissue boundaries and areas with inaccurate field measurements. In this paper, a novel MR-EPT approach is proposed, which is based on a direct solution to Maxwell's curl equations. The distribution of EPs is calculated by iteratively fitting the RF field calculated by the finite-difference-time-domain (FDTD) technique to the measured values. To solve the time-consuming problem of the iterative fitting, a graphics processing unit (GPU) is used to accelerate the FDTD technique to process the field calculation kernel. The new EPT method was evaluated by investigating a numerical head phantom, and it was found that EP values can be accurately calculated and were relatively insensitive to simulated RF field errors. The feasibility of the proposed method was further validated using phantom-based experimental data collected from a 9.4 Tesla (T) Magnetic Resonance Imaging (MRI) system. The results also indicated that more accurate EP values could be reconstructed from the new method compared with conventional methods. Moreover, even in the absence of phase information of the RF field, the proposed approach is still capable of offering robust EPT solutions, thus having improved practicality for potential clinical applications.