Simulation of beam hardening in X-ray tomography and its correction using linearisation and pre-filtering approaches

Abstract

CTBeam hardening is one of the major artefacts, which arises due to the polychromatic nature of the X-ray source, that reduces the quality of the reconstructed image in X-ray computed tomography. This paper describes the simulation of a tomogram with beam hardening and its correction using linearisation and pre-filtering methods. The simulation studies show that 70% of the maximum energy is required for full object penetration and to obtain minimum beam hardening. Also, the pre-filtering offers better beam hardening correction due to the removal of low-energy photons. The simulation results are found to be in good agreement with the experimental results. After beam hardening correction, 3D visualisation and dimensional analysis of a stator motor core specimen has been demonstrated.

A Review of Common Beam Hardening Correction Methods for Industrial X-ray Computed Tomography

“…The MC simulation is always used as an evidence factor in experimental setup to obtain trusted results by comparing with experimental measurements to be sure about the degree of accuracy of the measurements. Many simulation codes are used in the field of x-ray computed tomography, for example, Geant4, EGS4 and MCNP (Arunmuthu et al 2013;Kitazawa et al 2005). Beam hardening correction using MC simulation can be carried out in three stages: First, simulate the photon transmission process with exact material geometry to obtain the energy spectrum curve of the material.…”

“…The final step is a reconstruction of the image by using this effective energy to generate monochromatic projection data (Thomsen et al 2015). This method if chosen to be applied requires knowledge about the detector efficiency and the energy spectrum MC simulation which has been extensively used for investigation of beam hardening artifact in many studies such as Arunmuthu et al (2013), Lifton et al (2013), Ramakrishna et al (2006), Sahebnasagh et al (2012), Tan et al (2014), Thomsen et al (2015) and Yan et al (2000). It has high precision and is very flexible regarding changes in the beam geometry, sample composition, objects geometry and densities.…”

“…That is because, the internal area of an object are traversed by X rays with energy higher than the edge area, which makes the edges more attenuating than internal areas. However, the CT value of the central image is lower than the edge area, with the shape of the Cup appears in the middle dark edge, also called the cup artifacts, Figure 2 schematic explains the shape of cupping artifacts, that originally coming as an error in the attenuation coefficient, a percentage error can be calculated by Ketcham and Hanna (2014) and Arunmuthu et al (2013),…”

“…FIGURE 2. The schematics illustrating profile of grey level for image reconstruction in case of polychromatic image and image corrected form hardening artifact (Arunmuthu et al 2013) Therefore, reconstruction of an image needs a precise attenuation map, of the object under investigation. Therefore, an attenuation error coming from beam hardening must be corrected because an image quality can be significantly improved and a grey value of the same material appears identical after reconstruction.…”

Profile imaging of actual defects in steel plate based on electromagnetic ultrasonic SH guided wave scattering

“…ln recent years, ElJGW imaging technique has been developed to obtain more detailed information about defects [15-1 6]. Guided wave tomography imagi ng exploits an array of transducers to transmit and receive a group of guided wave rays and reconstructs the defect image using the projection data [17][18][19]. When guided wave e ncounters defects and strong scattering happens, the effect of scatteri ng will dominate a nd lead to much artifacts on the reconstructio n image of defects, w hi ch severely d egrades the positioning acc uracy and image quality of defects obtained by traditional guided wave imaging m ethods [20].…”