22 March 2010 Improved CT image quality using a new fully physical imaging chain
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Abstract
This paper describes the image quality improvements achieved by developing a new fully physical imaging chain. The key enablers for this imaging chain are a new scatter correction technique and an analytic computation of the beam hardening correction for each detector. The new scatter correction technique uses off-line Monte Carlo simulations to compute a large database of scatter kernels representative of a large variety of patient shapes and an on-line combination of those based on the attenuation profile of the patient in the measured projections. In addition, profiles of scatter originating from the wedge are estimated and subtracted. The beam hardening coefficients are computed using analytic simulations of the full beam path of each individual ray through the scanner. Due to the new approach, scatter and beam hardening are computed from first principles with no further tuning factors, and are thus straight forward to adapt to any patient and scan geometry. Using the new fully physical imaging chain unprecedented image quality was achieved. This is demonstrated with a special scatter phantom. With current image correction techniques this phantom typically shows position dependent inhomogeneity and streak artifacts resulting from the impact of scattered radiation. With the new imaging chain these artifacts are almost completely eliminated, independent of position and scanning mode (kV). Further preliminary patient studies show that in addition to fully guaranteeing an absolute Hounsfield scale in arbitrary imaging conditions, the new technique also strongly sharpens object boundaries such as the edges of the liver.
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Jens Wiegert, Matthias Bertram, Steffen Wiesner, Richard Thompson, Kevin M. Brown, Thomas Morton, Tsvi Katchalski, Yoad Yagil, "Improved CT image quality using a new fully physical imaging chain", Proc. SPIE 7622, Medical Imaging 2010: Physics of Medical Imaging, 76221I (22 March 2010); doi: 10.1117/12.844564; https://doi.org/10.1117/12.844564
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