Investigation Of Measurement System For Biological Tissue Based On Magnetic Induction Tomography

Magnetic Induction Tomography, a kind of imaging technology for measuring the distribution of biological tissue's electrical impedance or conductivity by applying the theory of electrical magnetic field detecting. Besides common advantages of EIT, such as harmlessness, convenience and small in type, MIT technique is sensitive to the center position of the imaging region, which makes MIT very prospective in imaging the inner tissues. Because MIT uses the magnetic field as the media in measurement and the magnetic field can go through the skull easily, the negative effects of skull with high impedance are avoided. The non-contact way of MIT makes it very prospective in medical measurement, especially in detecting the pathological changes in the skull. Current methods and existing problems of electrical impedance Tomography and magnetic induction tomography are presented in details. Then, the principles of three different kinds of MIT methods are presented respectively. And the electromagnetic background of the chosen method is analyzed, upon which, the feasibility and the superiority of the MIT method is proved in theory.In this paper, on the development of the measurement hardware is described in detail. By analyzing the characteristic of the weak signal induced by the organism and tissue, the idea of capturing the signal's relative change is obtained. A measurement system is developed, which consists of a sine wave signal source; a power amp, driving the excitation coil of the sensor; a sensor, transmitting alternating primary magnetic field and picking up the secondary magnetic signal; a nulling circuit, providing a nulling reference signal; a lock-in amp, picking up the wanted signal; a controller, controlling the whole system.A series of tests were carried out by measuring NaCl brine, which nearly has the same conductivity with the normal human brain tissue. Results verified the feasibility of this method, in addition, error analysis and possible improvement to this method are presented in the end.