【作者】 向胜昭；

【导师】 黄卡玛；

【作者基本信息】 四川大学 ， 无线电物理， 2005， 硕士

【摘要】 磁感应成像(MIT,magnetic induction tomography)是利用磁感应检测原理对生物组织电阻率(电导率)的空间分布进行成像,这一方法也被称为电磁成像(EMT,electromagnetic tomography)。磁感应成像技术对生物体的研究具有重要意义。该技术具有无损伤、信息丰富、非接触性、中心敏感性和可连续监测性等优点,具有广阔的应用前景。但是,MIT技术还存在诸多的技术困难,最主要的困难是在极强的初级磁场背景下,难以检测到极弱的次级磁场有用信号。 本课题组针对该问题,提出利用三维磁场聚焦的办法来克服这一困难,提高成像系统检测有用信号的敏感性。本文的主要工作是寻求合适的激励线圈,实现三维磁场聚焦磁感应成像。 本文利用矩形平面螺旋线圈作激励线圈,详细分析了磁感应成像中激励线圈产生的磁场数学模型;并编程计算了平面螺旋线圈作激励线圈产生的磁感应强度的分布,计算结果与利用有限积分软件计算结果吻合;计算了线圈的电感,结果与近似公式计算得出的电感值吻合:数值模拟了生物组织对线圈电阻和电感的影响;并对利用三维磁场聚焦技术的磁感应成像的反演算法作了初步研究。在以上工作基础上,我们得到矩形平面螺旋线圈产生的磁场具有聚焦特性的结论,认为用矩形平面螺旋线圈来做生物组织电导率成像技术的激励线圈是可行的,但其检测灵敏度随生物组织的深度而下降。 本文还针对几种典型的线圈,利用有限积分类软件计算了其磁感应强度分更多还原

【Abstract】 Magnetic induction tomography is a technique to image the electrical conductivity distribution within the biological tissue. This technique has been variously named mutual inductance tomography (also MIT) or electromagnetic tomography (EMT). The technique has attracted interest for biomedical application due to the non-contacting measurements, which may provide advantages over electrode based impedance tomography in certain applications. It is a new imaging modality being developed for the process industry and for medical imaging. Although some research groups have done more and more work on this technique, it is far from perfect up to the present. A number of experimental systems exist, but so far no magnetic induction tomography system has reached routine use either industrially or medically.There is much great difficulty about magnetic induction tomography that is not solved now. A major problem to be overcome in developing a practical biomedical magnetic induction tomography system is to accurately measure the small perturbation of the received signal due to the induced eddy currents given the relatively low conductivity of biological tissue. This paper describes a new idea that was presented by our research groups on how to accurately measure the small perturbation. The idea is that magnetic induction tomography system based on the technique of 3D focused magnetic field can accurately measure the small perturbation.The inductance of the rectangular plan spiral coil is calculated in this paper.The calculated results are in agreement with the results calculated by approximate formula. It is found that the magnetic fields generated by the rectangular plan spiral coil can focus in a small area. The changes of inductance and resistance by the conductivity of biological tissue are calculated also. Furthermore, the forward problem and inverse problem of magnetic induction tomography were analyzed simply in this paper.The magnetic field generated by several kinds of coils was calculated. The changes of inductance and resistance by the conductivity of biological tissue are calculated also. It is found that the magnetic fields generated by the conical spiral coil can focus in a very small area and the conical spiral coil is best choice of the exciting coil for magnetic induction tomography of biological tissue. The magnetic fields generated by the coronary spiral coil can also focus in a very small area. Further more, it will be advantageous to measure the conductivity of the brain if the coronary spiral coil is used as the exciting coil for magnetic induction tomography .更多还原