Electrolytic fabrication of Bi nanowires and empirical water precorrection in C-arm computed tomography
Daniel Schönke (Universität Heidelberg)

Aim of my bachelor thesis was the electrolytic fabrication of Bismuth nanowires in polycarbonate templates, motivated by the interesting electronic properties of this metalloid, which depend strongly to the size of the probes and the temperature. Because of the long mean free path length in this material, Bismuth nanowires have electronic transport properties like a one-dimensional conductor. For the electrolysis gold was evaporated on the multi-pore polycarbonate membrane and used as cathode. During the electrolytic process the Bismuth ions in the electrolyte were transported into the pores and deposited there. The resulting nanowires were evaluated by electron microscopy.

During my master thesis I implement and evaluate an image quality enhancing algorithm for computed tomography. Cupping and streak artifacts occur due to the polychromatic radiation of the x-ray source. We apply an empirical cupping correction method without necessary a priori knowledge at the measured data of the cone-beam flat-panel detector system Siemens Artis Zeego for linearizing the attenuation data. Therefore a polynomial precorrection function is used, whose coefficients are determined by fitting a linear combination of reconstructed images of a water phantom to a defined template that equals the expected result with a monoenergetic spectrum. Given the precorrection coefficients the correction can be applied timesaving in the projection-domain.