Effects of iterative reconstruction on image quality and patient dose in computed tomography

In this thesis, the effects of iterative reconstruction algorithms on image quality and patient dose were investigated. PET / CT tomography device in Yeditepe University Specialized Hospital was used. In the abovementioned system, both unfiltered back projection and iterative reconstruction algorithm can create tomography. Computed tomography dose index (CTDI) values, CTDI phantom, and 10cm pen-type ion chamber were used for different irradiation parameters. Cathpan 600 phantom was chosen for image quality evaluation. Evaluation of image quality parameters (free software) was performed using IMAGE J and IQ WORK software. The irradiation parameters of the tomography system were 120 kVp and chosen three different mA values. CTDI values for these different mA values were measured and compared with the values given by the system. Both 2,5 mm and 5 mm tomographic sections were obtained. Filtered back projection and iterative reconstruction parameters were obtained at 20,40,60,80 and 100 values by using standard and detail filters of Catphan 600 phantom. Image quality parameters such as CNR, SNR, MTF, and homogeneity were evaluated for all reconstruction methods from Catphan 600 phantom images. Finally, iterative methods can be used to reduce the dose while preserving the image quality and it is also recommended to take the clinic under these conditions. Different quantitative image quality parameters at different dose levels were evaluated by the CT component of the PET / CT in the Nuclear Medicine Department of Yeditepe University Specialized Hospital besides obtained tomography kept the irradiation conditions low with the same image quality. Key words: Iterative Reconstruction, Iterative Reconstruction Algorithms, Computed Tomography.