【作者】 郭忠海；

【导师】 黄卡玛；

【作者基本信息】 四川大学 ， 无线电物理， 2002， 硕士

【摘要】 在生物医学工程中，应用电磁场数值计算方法研究电磁场与生物体相互作用的规律是一个十分重要的课题。它既有利于电磁波在医学上的应用，又可以有效地提供可靠的资料和数据，以避免出现不必要的伤害事故。本文提出了生物医学工程中两种对生物组织进行电磁诊断的新方法，并分别进行了数值分析，对其实际应用进行了探讨。 本文首先基于低频电磁成像方法的正问题，给出了在准静场近似下，三维有耗媒质在低频激励线圈作用下的二次磁场的计算方法，讨论了电导率的不均匀分布对二次磁场的扰动情况。计算实例的结果表明，充分利用有限元方法中产生的系数矩阵高度稀疏并呈带状对称分布的特点，采用特殊的存储技术，可以大大提高计算效率。该方法为一种有效的正问题计算方法，可直接应用于需要利用二次磁场信息反演有耗媒质分布的正问题计算。再结合适当的反演算法就可实现电磁成像的目的，从而达到医学诊断的目的。 在对矩形微带天线用于分层生物组织诊断的FDTD分析中，讨论了在微带天线近场作用下，分层生物组织内的场分布；生物组织中肿瘤大小以及肿瘤的介电特性与微带内反射系数的关系及相应的场分布，为不同肿瘤的辨别提供了一定的依据；还讨论了不同生物组织在不同频率的近场作用下的频率特性。在用FDTD方法计算电磁场分布的过程中，采用一种新的微带线馈电激励设置方式，使得在计算过程中源平面无需切换成吸收边界，由于场的划分使反射场自然从总场分离出来。为了提高计算精度，截断边界采用一种新型的完全匹配吸收层作为吸收边界，取得了较好的数值结果。更多还原

【Abstract】 It is very important to investigate interaction between electromagnetic field and biological tissues using numerical methods in Biomedical Engineering. The investigation is helpful for the application of the electromagnetic field in the medical works, and it can also provide useful data and information to avoid unnecessary hurt and accident. In this paper, two new diagnosis methods are presented and analyzed using two different numerical methods respectively.A new low-frequency 3D electromagnetic imaging method excited by a coil is discussed. And the forward problem is solved using Finite Element Method (FEM). A designed example is given, and results show that this method is effective for solving the forward problem. This is very helpful and useful for the design of the imaging system.In another diagnosis method, microwave reflection characteristics of a microstrip antenna applicator contacted with layered biological tissues are analyzed by using FDTD method. Three-layer tissues model, which is consisted of thin skin, fat and the semi-infinite muscle, is adopted. A spherical tumor with the different permittivity from the surrounding normal muscle tissue is assumed to exist inside the muscle tissue. Simulation results show that the difference of the permittivity between the tumor and the normal muscle tissue can be detected through microwave reflection measurement. The relationship between the reflection characteristics of the antenna and sizes of tumors is also discussed. Numerical results show that the position of the tumor can be determined by measuring the reflection of the antenna. This technique can be applied to general examination and early diagnosis of thesubcutaneous tumor. In the analysis process, some special method such as setting the excitation source and a new perfectly matched layer is applied.All the results above are useful for the further research in the electromagnetic diagnosis methods in the Biomedical Engineering.更多还原