Department of Electronics and Electrical Engineering, University of Bath, Bath, UK.
Physiol Meas. 2012 May;33(5):863-79. doi: 10.1088/0967-3334/33/5/863. Epub 2012 Apr 24.
Magnetic induction tomography (MIT) is a new and emerging type of tomography technique that is able to map the passive electromagnetic properties (in particular conductivity) of an object. Excitation coils are used to induce eddy currents in the medium, and the magnetic field produced by the induced eddy current is then sensed by the receiver coils. Because of its non-invasive and contactless feature, it becomes an attractive technique for many applications (especially in biomedical area) compared to traditional contact electrode-based electrical impedance tomography. Due to the low contrast in conductivity between biological tissues, an accurate and stable hardware system is necessary. Most MIT systems in the literature employ external signal generators, power amplifiers and highly stable down-conversion electronics to obtain a satisfactory phase measurement. However, this would increase design complexity substantially. In this paper, a National Instrument-based MIT system is developed at the University of Bath, aiming for biomedical applications. The system utilizes National Instrument products to accomplish all signal driving, switching and data acquisition tasks, which ease the system design whilst providing satisfactory performance. This paper presents a full-scaled medical MIT system, from the sensor and system hardware design, eddy current model verification to the image reconstruction software: the performance of this MIT instrumentation system is characterized in detail, including the system accuracy and system stability. The methods of solving eddy current problem are presented. The reconstructed images of detecting the presence of saline solutions are also included in this paper, which show the capability of national instrument products to be developed into a full-scaled biomedical MIT system, by demonstrating the practical experimental results.
磁感应断层成像（MIT）是一种新兴的层析成像技术，能够对物体的被动电磁特性（特别是电导率）进行成像。激励线圈用于在介质中感应涡流，然后通过接收线圈感应涡流产生的磁场。由于其非侵入性和非接触式的特点，与传统基于接触电极的电阻抗断层成像相比，它成为许多应用（特别是在生物医学领域）的一种有吸引力的技术。由于生物组织的电导率对比度低，因此需要一个准确和稳定的硬件系统。文献中的大多数 MIT 系统都采用外部信号发生器、功率放大器和高稳定度下变频器来获得满意的相位测量。然而，这会大大增加设计的复杂性。本文介绍了巴斯大学开发的基于美国国家仪器的 MIT 系统，旨在应用于生物医学领域。该系统利用美国国家仪器的产品来完成所有的信号驱动、开关和数据采集任务，简化了系统设计，同时提供了满意的性能。本文介绍了一个全规模的医疗 MIT 系统，从传感器和系统硬件设计、涡流模型验证到图像重建软件：详细描述了该 MIT 仪器系统的性能，包括系统精度和系统稳定性。还介绍了解决涡流问题的方法。本文还包括了检测盐溶液存在的重建图像，这些结果展示了美国国家仪器产品开发成为一个全规模的生物医学 MIT 系统的能力，通过演示实际的实验结果。
