Beam Hardening Correction for Computed Tomography Images Using a Postreconstruction Method and Equivalent Tisssue Concept

Abstract

A postreconstruction method for correcting the beam-hardening artifacts in computed tomography (CT) images is proposed. This method does not require x-ray spectrum measurement. The authors assumed that a pixel in a CT image can be decomposed into equivalent tissue percentages, depending on its CT number. A scout view of the step wedges made of these equivalent tissues was performed to obtain a beam-hardening correction curve for each tissue. Projecting through the CT image from various angles generated simulated projection data and the total thickness of each tissue along the ray. The correction term was estimated using the tissue thickness traveled by the ray, and this term was then added to its corresponding projection data. A second reconstruction using the corrected projection data yielded a beam-hardening corrected image. The preliminary results show that this method reduces beam hardening artifacts by 14% for aluminum and increased the object contrast by 18% near the aluminum-water boundary. The variation in CT numbers at different locations were reduced, and the aluminum CT number also was restored.

Effects of CPP-ACP with sodium fluoride on inhibition of bovine enamel demineralization: A quantitative assessment using micro-computed tomography

“…Beam-hardening leads to an apparent higher attenuation near the periphery of an otherwise homogeneous sample material. 26,36,37 Beam-hardening artifacts can be reduced by filtering out the low-energy radiation or pre-hardening the beam using attenuating metal filters (aluminum, copper or brass). 26,34 In the present study, we used a 0.2-mm-thick brass (Cu-Zn) filter.…”

Characterization and correction of cupping effect artefacts in cone beam CT

“…The atomic number of aluminium and the effective atomic number of cortical bone are similar; therefore, conclusions may be drawn on the effect of beam hardening correction on aluminium from its effect on cortical bone and vice versa. 18 Owing to the fact that our phantom is larger in diameter and thickness than the phantom used by Meganck et al, 7 the cupping effect should initially be worse in our 3.8 cm cylindrical aluminium phantom and therefore more difficult to eliminate. Meganck et al 7 used a phantom of 11.811 mm in diameter and demonstrated that the cupping effect due to beam hardening increases as phantom thickness increases.…”

“…The make up of aluminium 6061 alloy consists of 98% aluminium, 1% magnesium and 0.6% silicon. 18 The aluminium cylinder was centred within the field of view (FOV) for all image acquisitions. The cupping effect was demonstrated using a line profile plot of the grey level values with ImageJ software (National Institutes of Health, Bethesda, MD).…”

Beam hardening correction using a conical water-equivalent phantom for preclinical micro-CT

“…A third approach towards beam hardening correction is to calibrate the measured projection data to that of a known material and geometry, assuming that the subject consists of mainly one type of material or similar substances [5]. Since the exact calibration function may not exist or may be impractical to find, a polynomial is often used to approximate the function in practice.…”