论文标题
MRI中的广义信号模型和直接基于FID的介电参数检索
Generalized Signal Models and Direct FID-Based Dielectric Parameter Retrieval in MRI
论文作者
论文摘要
在本文中，我们提出了用于磁共振成像（MRI）中磁场测量值的全波信号模型。我们的分析是基于散射形式主义，在该形式主义中，通过电散射源考虑物体或身体的存在。我们表明，可以评估这些信号模型，只要绿色的背景字段的张量与对象的介电参数以及对象激发部分内的磁化相关。此外，在一个嵌入在自由空间中的小均匀球的情况下，明确的信号表达式得出了，可以应用准静态近似值。球的电导率和介电常数在结果信号模型中作为显式参数出现，并使我们能够研究测得的信号相对于这些介电参数的敏感性。此外，对于自由感应衰减信号，我们表明，在某些条件下，可以从基于电气或磁场测量值的噪声污染的感应衰减信号中检索球的介电参数。
In this paper we present full-wave signal models for magnetic and electric field measurements in magnetic resonance imaging (MRI). Our analysis is based on a scattering formalism in which the presence of an object or body is taken into account via an electric scattering source. We show that these signal models can be evaluated, provided the Green's tensors of the background field are known along with the dielectric parameters of the object and the magnetization within the excited part of the object. Furthermore, explicit signal expressions are derived in case of a small homogeneous ball that is embedded in free space and for which the quasi-static Born approximation can be applied. The conductivity and permittivity of the ball appear as explicit parameters in the resulting signal models and allow us to study the sensitivity of the measured signals with respect to these dielectric parameters. Moreover, for free induction decay signals we show that under certain conditions it is possible to retrieve the dielectric parameters of the ball from noise-contaminated induction decay signals that are based on electric or magnetic field measurements.
