Verifying of the multi-frequency current source for electrical impedance tomography

Abstract

Electrical impedance tomography (EIT) is a new medical image technology; it has the advantages of no irradiation hazard, low cost and real time monitoring. In EIT system, it is import to support the stable current source for obtaining the image quality. From the literatures, there are three kinds of the circuit type proposed frequently. The six different opamp devices with different frequency response are used as simulating devices. Then the results simulated support us to design the current source of the multi-frequency EIT system. The preliminary results are as follows: 1.The difference between results simulated when using the different circuit types based on the same op-amp device is not obvious. 2. The difference between results simulated when using the different opamp devices with different GBW and SR based on the same circuit type is apparent. 3. When varying the load resistance and fixing work frequency of 1MHz, the variation of output current is less than ±0.00008%. 4. The circuit has output impedance ranging from 7.5Mω to 100kω for the three kinds of circuit type when using THS4021 device. Then output impedance of 90kω is obtained when using LM833 and LM741 devices. 5. The one-op-amp circuit type and the high-frequency response device are used for designing the multi-frequency VCCS with frequency response ranging of up to 1MHz. © 2008 Springer-Verlag.