Avancerade datorsimuleringar av fotonräknande spektral CT för utvärdering av krosstalförvrängningar

Photon-counting computed tomography (PCCT) represents a significant advancement in medical imaging, as it promises higher spatial resolution, spectral imaging capabilities, and reduced radiation dose compared to conventional CT. GE HealthCare is developing an innovative photon-counting detector made of silicon, called the Deep-Silicon Detector, which employs a new edge-on geometry that ensures sufficient detection efficiency. Photoncounting detectors are direct conversion and in general there are no physical barriers between pixels, which allows for crosstalk due to charge sharing and X-ray scattering inside the detector, producing so-called crosstalk artifacts. The Deep-Silicon Detector is equipped with tungsten sheets between the sensors that block cross talk in the slice direction of the detector, but thereare no barriers in the pixel direction. Hence, cross talk remains a major challenge in achieving high-quality reconstructed images and, if not corrected for, poses diffculties from a clinical perspective as well. This thesis focuses on characterizing and explaining the origins of these artifacts, simulating crosstalk inside the detector, and validating the accuracy of the CatSim simulation software, developed by GE HealthCare, in reproducing crosstalk artifacts in clinical images through direct comparison with real images. The work is closely related to the development of a correction algorithm for crosstalk artifacts, as the ability to simulate a phenomenon makes it possible to solve the inverse problem and build such an algorithm. For the simulations, KTH’s supercomputer Dardel was employed, enabling the exploration ofparallelization strategies to optimize the computational effciency of CatSim. The findings confirm that we are able to simulate crosstalk inside the detector, but CatSim can reproduce crosstalk artifacts only to a certain extent. This highlights the need to incorporate more complex phenomena into the simulation before drawing definitive conclusions regarding CatSim’s accuracy and obtaining more realistic artifact representations.