Complete Scheme for Beam Hardening Correction in Small Animal Computed Tomography

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Ieee - The Institute Of Electrical And Electronics Engineers, Inc
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CT images are often affected by beam hardening artifacts (cupping and dark streaks) due to the polyenergetic nature of the X-ray beam. FDK is still the favorite reconstruction algorithm in commercial X-ray CT scanners. Several correction methods have been proposed to be included in an FDK reconstruction scheme. We present a complete correction scheme for beam hardening artifact correction in an FDK based reconstruction scenario that accounts for both cupping artifact and dark streaks avoiding the need of the knowledge of the source spectrum. The proposed correction scheme includes two steps: a linearization step of projection data and a post-reconstruction step. The first step assumes that the object is homogeneous and uses a linearization function that is calculated empirically in a previous calibration process with a simple phantom. The second step is based in the theoretical study described in Joseph and Spital, and calculates the non-linear beam-hardening distortion from a bone segmentation of the reconstructed image. The proposed correction scheme was evaluated in real studies acquired with a cone-beam micro-CT scanner: three polymethylmethacrylate cylinders (3, 4, and 6 cm diameter), a two-density cylindrical phantom and three rodent studies. Results show an average cupping reduction of 84 % in the three homogeneous phantoms and an average dark streaks reduction of 80 % in the two-density phantom and the three rodent studies. The proposed method could be incorporated easily in any cone beam micro-CT scanner and substitutes the need of the knowledge of the spectrum by empirical measurements and two parameters. Since it is based on empirical measurements, we expected to correct the artifacts derived from scattering.
Proceedings of: 2012 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC). Anaheim, California, USA. October 29 - November 3, 2012
Computerised tomography, Diagnostic radiography, Image reconstruction, Medical image processing, Phantoms
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Bo Yu (ed.) (2012). 2012 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC): Anaheim, California, USA. October 29 - November 3, 2012 . IEEE, 3835-3838