18 March 2015 Physics-based modeling of computed tomography systems
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Abstract
We present a theoretical framework describing projections obtained from computed tomography systems considering physics of each component consisting of the systems. The projection model mainly consists of the attenuation of x-ray photons through objects including x-ray scatter and the detection of attenuated/scattered x-ray photons at pixel detector arrays. X-ray photons are attenuated by the Beers-Lambert law and scattered by using the Klein-Nishina formula. The cascaded signal-transfer model for the detector includes x-ray photon detection and light photon conversion/spreading in scintillators, light photon detection in photodiodes, and the addition of electronic noise quanta. On the other hand, image noise is considered by re-distributing the pixel signals in pixel-by-pixel ways at each image formation stage using the proper distribution functions. Instead of iterating the ray tracing over each energy bin in the x-ray spectrum, we first perform the ray tracing for an object only considering the thickness of each component. Then, we assign energy-dependent linear attenuation coefficients to each component in the projected images. This approach reduces the computation time by a factor of the number of energy bins in the x-ray spectrum divided by the number of components in the object compared with the conventional ray-tracing method. All the methods developed in this study are validated in comparisons with the measurements or the Monte Carlo simulations.
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Hanbean Youn, Ho Kyung Kim, Soohwa Kam, Seung Ho Kim, Ji Woong Park, Hosang Jeon, "Physics-based modeling of computed tomography systems", Proc. SPIE 9412, Medical Imaging 2015: Physics of Medical Imaging, 94122N (18 March 2015); doi: 10.1117/12.2081827; https://doi.org/10.1117/12.2081827
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