Golam Dastegir Al-Quaderi

A noninvasive and radiation free technique for in-vivo measurement of the volume of organs or fluids in the human body is necessary for many clinical applications. Focused Impedance Method (FIM) is a novel technique of electrical impedance measurements which has enhanced sensitivity in a localized region. FIM can sense the change in transfer impedance of an organ within a reasonable depth of the human body using surface electrodes, minimizing contributions from its neighbouring regions. This of course assumes that the impedance properties of the embedded object are different from that of its surrounding tissues. This paper presents a new method for the determination of the volume of an organ within body using dual electrode separations of a concentric 4-electrode FIM configuration. In order to develop this formalism simulated FIM measurements using surface electrodes on a cubic volume conductor with embedded spherical objects were performed using a Finite Element (FE) based simulation software, COMSOL Multiphysics ®. For the present methodology, the conductivity of the object with respect to its surroundings and its depth need to be known. The former is obtainable through some primary invasive or in vivo measurements while the latter may be approximated using anatomy. Experimental results on a phantom made up of a cubic tank filled with saline showed that the proposed method can be used to determine the volume of embedded objects to an accuracy of about 5% which is adequate for most physiological measurements. The technique may also find use in geology, oceanography and industry.

In this article, at first we propose a unified and compact classification of single negative electromagnetic metamaterial-based perfect transmission unit cells. The classes are named as: type-A,-B and-C unit cells. Then based on the classification, we have extended these ideas in semiconductor and graphene regimes. For type-A: Based on the idea of electromagnetic Spatial Average Single Negative bandgap, novel bandgap structures have been proposed for electron transmission in semiconductor heterostructures. For type-B: with dielectric-graphene-dielectric structure, almost all angle transparency is achieved for both polarizations of electromagnetic wave in the terahertz frequency range instead of the conventional transparency in the microwave frequency range. Finally the application of the gated dielectric-graphene-dielectric has been demonstrated for the modulation and switching purpose.

Subcutaneous fat layer thickness in the abdomen is a risk indicator of several diseases and disorders like diabetes and heart problems and could be used as a measure of fitness. Skinfold measurement using mechanical calipers is simple but prone to error. Ultrasound scanning techniques are yet to be established as accurate methods for this purpose. magnetic resonance imaging (MRI) and computed tomography (CT) scans can provide the answer but are expensive and not available widely. Some initiatives were made earlier to use electrical impedance to this end, but had inadequacies. In the first part of this paper, a 4-electrode focused impedance method (FIM) with different electrode separations has been studied for its possible use in the determination of abdominal fat thickness in a localized region. For this, a saline phantom was designed to provide different electrode separations and different layers of resistive materials adjacent to the electrodes. The background saline simulated the internal organs having low impedance while the resistive layers simulated the subcutaneous fat. The plot of the measured impedance with electrode separation had different 'slopes' for different thicknesses of resistive layers, which offered a method to obtain an unknown thickness of subcutaneous fat layer. In the second part, measurements were performed on seven human subjects using two electrode separations. Fat layer thickness was measured using mechanical calipers. A plot of the above 'slope' against fat thickness could be fitted using a straight line with an R(2) of 0.93. Then this could be used as a calibration curve for the determination of unknown fat thickness. Further work using more accurate CT and MRI measurements would give a better calibration curve for practical use of this non-invasive and low-cost technique in abdominal fat thickness measurement.