Improving image quality of a mobile Cone-Beam CT by use of scatter and beam-hardening corrections

摘要

Cone-beam computed tomography (CBCT) imaging system has been widely used in various applications, and takes an important role for diagnosis of emergency patient. However large size of detector causes high scatter-to-primary ratios on CBCT projection data. Also, beam hardening artifacts in reconstructed CT images is resulted by the polychromatic spectrum of X-ray beam. These two phenomena lead to unwanted results of reconstructed image such as cupping artifact, worsen soft tissue contrast, and lower CT grey value. This paper studies the result of investigation into the effect of the scatter kernel superposition (SKS) method and polynomial beam hardening correction on the measurement soft tissue contrast of head phantom for reconstructed data from half-fan CBCT system. The measurement imaging system was PHION, which is mobile CT system of NanoFocusRay Co., Ltd, and PH-3 angiographic CT head phantom ACS was used for experiments at 120 kVp and 15 mAs. The data was processed by scatter correction and beam hardening correction which is a linearization method based on polynomial curves of second order. The image was reconstructed using a filtered back projection algorithm. After scatter and beam hardening correction, contrast to noise ratio of reconstructed images is increased and soft tissues are seen more clearly. Image with scatter correction and beam hardening correction has clear boundary between skull and soft tissues, but only scatter corrected image has unclear boundary.