Eddy Current Sensor for Tissue Conductivity Measurement

Electrical conductivity of the tissue can be measured via eddy current sensor and it can be used to distinguish cancerous tissue from healthy tissue. The conductivity of healthy and cancerous tissues is different due to the strong correlation between necrosis in tumor and the associated membrane breakdown [10]. Three types of similar electronic set ups with different components based on eddy current technique were investigated to measure electrical properties of tissue in vitro as well as test and evaluate the electronic set ups. This papre describes new application of eddy current sensor, one of basics of non destructive testing, NDT, in biomedical engineering. For medical purposes, conductivity of tissue or tissue equivalent samples is evaluated and compared with other specimens via sensor based on eddy current techniques. To reach the aim, the electronic set ups are evaluated via measurements on targets with predetermined conductivities. Eddy current was induced in targets by magnetic field of the coil and that eddy current generated a secondary magnetic field which opposed the primary magnetic field and affect the inductance and consequently the impedance of the coil. The measured output (RMS-value or its amplitude) from bridge circuit is correlated to the change in coil's inductance and impedance and those are proportional to change in conductivity of the targets. Prominent sensor characteristics such as quality factor, inductance and operating frequency considered to be high enough and desired sensor dimensions are assessed