and all of my friends, my teachers who have braced love on me tremendously and inspired me unconditionally over the years. In this very important occasion, I would like to remember late Professor Khodiza Adib Khanum, who passed away in 2009, for her guidance and adoration during my childhood. Her motivation for research work led me to take up the current study in the field of Biomedical Physics. Finally, I am immensely grateful to my husband Mustafa Mamun for his continuous inspiration and motivation during the entire period of the present work. In reality, no word can narrate his contribution to this work. All can be said is, without his constant love, sacrifice, support, care and patience, this thesis would have been impossible for me to complete.

Focused impedance measurements (FIM) are used in several fields, and address the problem of measuring the volume impedance of an object within a volume conductor. Several electrode configurations are possible, and these have different properties. Sensitivity fields of four configurations have been investigated. We present one new development of an existing FIM configuration, and we made finite element models of the configurations to analyse and compare them both graphically and numerically. The models developed have a variable-sized mesh that allows us to build complex models that fit easily in computer memory. We found that one configuration in particular, FIM4, was superior to the others in most aspects. We also analysed the effects of very high sensitivities in and under the electrodes. We found that even if the sensitivity is very high under the electrodes, the effects of inhomogeneities were not as high as one might expect.

Focused impedance measurement (FIM) is a technique where impedance can be measured with the optimum level of localization without much increase in complexity of measuring instrument. The electrodes are applied on the skin surface while the organs inside also contribute to the measurement, as the body is a volume conductor. In a healthy and disease free lung region, the air enters at breathe-in, increases the impedance of the lung, and impedance reduces during breathe-out. In contrast, for a diseased lung, where part of the lungs is filled with water or some fluid, air will not enter into this zone reducing impedance change between inspiration and expiration. With this idea, the current work had been executed to have general view of localized impedance change throughout thorax using 6-electrode FIM. This generated a matrix mapping from both the front and from the back of the thorax, which showed how impedance change due to ventilation varies from frontal plane to back plane of human bodies.

No abstract