On September 4 2020 Kristin Jensen at the Department of Physics defended the thesis “Iterative reconstruction in CT imaging; Image quality and radiation doses” for the degree of PhD (Philosophiae Doctor). The dissertation comes out of Faculty of Mathematics and Natural Sciences at University of Oslo. The title of the trial lecture was "Radiation risk for patients and operators in interventional CT".
Main research findings
Improved image quality in CT imaging using iterative reconstruction algorithms Image quality in CT imaging of liver and chest using different iterative reconstruction algorithms, behaved differently depending on dose level, anatomical region and reconstruction kernels. In general, image quality was improved with iterative reconstruction techniques compared to the reconstruction method used for forty years in CT imaging; filtered back projection. But there were also instances were image quality was degraded. Image noise was always reduced but often texture and resolution was changed making especially small lesions and structures with low contrast hard to depict. The changes also influenced the correlation between subjective evaluation and traditional quantitative measurements like image noise (standard deviation of Hounsfield units), contrast to noise ratios and signal to noise ratios. The implementation of iterative reconstruction techniques calls for new methods to quantitatively analyse images, since the reconstruction no longer is linear as is the case for filtered back projection.