Micro-CT for small animal imaging : Optimization of the tube voltage for low-contrast imaging

Abstract: This master thesis evaluated the optimal tube voltage for low-contrast imaging of a micro-CT system (intended for small animal imaging) built at the School of Technology and Health (STH) of the Royal Institute of Technology (KTH). The main goal of this work was to calibrate the above-mentioned device (composed moreover by a Hamamatsu microfocus L10951-01 X-ray tube, a CMOS flat panel Hamamatsu C7942CA-22 and using a Cone-Beam CT reconstruction algorithm) for obtaining the best imaging of low-contrast structures. In order to do this, an analytical model, re-adapted from the previous state-of-the-art Micro-CT studies, was evaluated for finding a sub-optimal tube voltage from which to start the experiments, done on a reference Low-Contrast phantom specifically intended for the calibration of Micro-CT devices.  Finally, by looking to the results from the experiments, a good tube setting for the optimization of the CT for low-contrast imaging was found. The optimal tube voltage for low-contrast imaging, from the experiments on the QRM phantom, was found to be between 48 and 50 kV. This tube voltage values gave the best CNR and contrast profiles results.  Ultimately, we found that the usage of a 1mm Al filtration reduced the absorbed dose without affecting the image quality.