chapter  61

Sensors for Electrical Impedance Tomography

WithTushar Kanti Bera, J. Nagaraju

In medical computed tomography (CT) [1] some kind of energy (such as x-rays, optical, electrical, sound, near infrared, etc.) is applied to the subject under test (SUT), and the modified or transformed form of the energy is collected or detected and compared with the incident one to reconstruct the spatial distribution of the tissue properties of the SUT called the parameters of interest (POI). The POI of the SUT gives anatomical, physiological (biophysiological or physiochemical), or pathological information. Hence, in medical tomographic imaging, the energy used to produce the image must penetrate the body tissues [2] to get information about the tissues. If the energy applied to the SUT does not experience any type of interaction (e.g., absorption, attenuation, scattering), the detected energy would 61-2not contain any useful information about the internal anatomy of the SUT [2]. Therefore, it would not be possible to construct an image of the anatomy using that information. In the x-ray computed tomographic technique, x-rays are applied to the boundary of the object under test, and the attenuated x-rays at the boundary are collected for the different projection angles to obtain a complete scan around a 360° rotation. Thus, the x-ray CT involves gathering the output x-rays (XOut) generated by applied x-ray signal (XIn) at the boundary from multiple directions and reconstructing the domain parameter relating the XOut to XIn (POI) using a software called reconstruction algorithm in a personal computer (PC).