Image b is the result of a software correction of the ring artifacts in a. Cera ct reconstruction and artifact reduction siemens. In todays connected world, software application resiliency takes an increasingly predominant role. Beam hardening effects are visible in the form of streak artefacts and cupping effects. The measurement hardware and software used for all measurements reported in. We derive the polynomial beam hardening correction, a method described in more detail elsewhere. In the past, many studies have been conducted to combat image artifacts induced by beam hardening. What does hardening phase mean in terms of software. The bonecorrection method has been widely adopted to compensate for beam hardening artifacts. Many commercially available software packages that are coupled with xray tomography systems offer a suite of options to apply prereconstruction beam hardening corrections. Beamhardening correction method based on original sinogram. The first proposed algorithm employs a statistical learning. It leads to various artifacts in reconstruction images and reduces image quality.
Beam hardening can also be correctedreduced during reconstruction. For example, one binary hardening technique is to detect potential buffer overflows and to substitute the existing code with safer code. Pdf software xray beam hardening correction of cylindrical. A level set method for cupping artifact correction in cone. L study conceptsstudy design or data acquisition or data. Higher order beam hardening artifacts, as they result when a mixture of materials such as water and bone, or water and bone and iodine is present, require an iterative beam hardening correction where the image is segmented into different materials and those are forward projected to. Beam hardening artifacts are highly undesirable for a medical diagnosis, because details in the reconstructed image are severely disturbed or completely lost. The bhc software algorithm used in this study was an imagebased correction approach that enables individual estimation of the beam hardening from highenhancing material and that from water for accurate calculation of the amount of beam hardening.
A ct artefact caused by computer errors due to sudden changes in tissue density, from a relatively low density in brain tissue to a high density in bone. Beamhardening correction methods for polychromatic xray. The application for electron beam hardening lies in treating surfaces with a hardening depth ranging from 0. We present a new method for correcting beam hardening artifacts in polychromatic xray ct data. Accordingly, it is a primary object of the present invention to provide an improved. Reducing beam hardening effects and metal artefacts using. Analysis and artifact correction for volume correlation measurements. The phenomenon of xray beam hardening bh has significant impact on preclinical microct imaging systems.
Development and quantitative assessment of a beam hardening correction model for preclinical microct by sucheta mohapatra a thesis submitted in partial fulfillment of the requirements for the master of science degree in biomedical engineering in the graduate college of the university of iowa december 2012. However, the facts that the xray beam produced by xray tube has a widely distributed energy spectrum and the absorption coefficient of materials has a dependence on photon energy result in beam hardening artifacts. This function is typically an exponential or polynomial of undetermined degree. Bouman are with the school of electrical and computer. Metal artifacts in computed tomography for radiation. Highfidelity artifact correction for conebeam ct imaging. Polychromatic ct data improvement with oneparameter power.
Engineering, purdue university, west lafayette, in 479070501 usa email. A correction table with both bone and tissue dimension was then developed. Artifacts and partialvolume effects utct university of texas. Metal artifact reduction for polychromatic xray ct based on a beam hardening corrector. Nov 27, 2001 there exists a need in the art of ct imaging and qct for an improved method of beam hardening correction.
On most industrial ct systems, software beam hardening correction employs some variety of linearization, which attempts to transform the polychromatic attenuation data into its monochromatic equivalent prior to image reconstruction. Optical engineering 507, 076501 july 2011 data consistency conditionbased beamhardening correction shaojie tang xian university of posts and telecommunications. Jul 01, 2011 in medical x ray computed tomography ct imaging devices, the x ray tube usually emits a polychromatic spectrum of photons resulting in beam hardening artifacts in the reconstructed images. A ct scan, or computed tomography scan is a medical imaging procedure that uses computerprocessed combinations of many xray measurements taken from different angles to produce crosssectional tomographic images virtual slices of specific areas of a scanned object, allowing the user to see inside the object without cutting.
Thus, the penetrating power of xray will continue to. The influence of beam hardening corrections are studied in section 6. Standard approaches to tomography reconstruction of the projection data registered with polychromatic emission lead to the appearance of cupping artifacts and irrelevant lines between regions of strong absorption. As a result, errors are present in the acquired line integrals or measurements of the attenuation coefficients of the scanned object. With more than 60 years experience, we manufacture these systems at our headquarters located in cambridge uk. The main reason for their appearance is the fact that part of the emission with low energy is being absorbed entirely by high absorbing objects. Beam hardening is a physical process that degrades the quality of ct images, introducing artefacts that are detrimental to visual inspection and automated segmentation algorithms. Data consistency conditionbased beamhardening correction article pdf available in optical engineering 507 july 2011 with 363 reads how we measure reads. Characterization and correction of beamhardening artifacts during. Asdip concrete software includes the design of multispan continuous beams based on the latest aci 318 provisions. This is the basis for short reconstruction times and excellent image quality alike. The application of beam hardening correction for industrial x. Following is an overview of the steps required to design continuous beams using asdip concrete. Filtration a flat piece of attenuating, usually metallic material is used to preharden the beam by filtering out the lowerenergy components before it passes through the patient.
Flowchart for frequency splitting accelerated iterative beam hardening correction. Beam hardening bh occurs when polychromatic radiation is. This function is typically an exponential or polynomial of undetermined degree or coefficient values. The brabant method compensates the hardening of xray beam by introducing two parameters in the forward projection process of the iteration. Additionally, form errors hinder dimensional evaluation. Electron beam systems for welding, drilling and hardening. Metal artifact reduction for polychromatic xray ct based on. A method for simultaneous image reconstruction and beam.
In addition to using different scanning technique parameters, the ct reconstruction software can add a beam hardening correction factor that can often be very effective at further reducing beam hardening artifacts. Machinelearningbased nonlinear decomposition of ct images. Toward comprehensive industrial computed tomography image. An iterative approach to the beam hardening correction in cone beam ct jiang hsieha applied science laboratory, ge medical systems, milwaukee, wisconsin 53201 robert c. Johnsonv i applied science laboratory, oe medical systems, milwaukee, wi 53201 zdepmtmcnt of diomedical engineering, marquette university, milwaukee, wi 53201 zablocki va medical center, milwaukee, wi 53201. Dec 10, 2015 the aim of this study was to develop a fast and accurate beam hardening correction method by modeling physical interactions between xray photons and materials for computed tomography ct imaging. In this paper, we present an iterative beam hardening correction approach for cone beam ct. A comparative study of two methods for the correction of beam.
In this work, we present an iterative scheme which signi. Binary hardening is a security technique in which binary files are analyzed and modified to protect against common exploits. The effect of beam hardening on resolution in xray microtomography article pdf available in proceedings of spie the international society for optical engineering 5370 may 2004 with 597 reads. Knowledge of these artifacts is important because they can mimic pathology e. Application of projection simulation based on physical imaging model to the evaluation of beam hardening corrections in xray transmission tomography s tang, x mou, y yang, q xu, h yu journal of xray science and technology 16 2, 95117, 2008. Beam hardening can be a pernicious artifact because it changes the ct value of a material or void depending upon its location in an image. The effect is conceptually similar to a highpass filter, in t. Tang et al data consistency conditionbased beamhardening correction fig.
The method described in this paper allows the correction of beam hardening artifacts in multimaterial objects. An improved beam hardening correction technique will provide qct measurements and ct images with improved accuracy. Existence of beam hardening artifact will degrade ct images, or even affects the applicability of the ct images. Beam hardening correction and its influence on the. Exploratory research into reduction of scatter and beam. In ct images of objects made of several materials with significant different attenuation characteristics these effects are even more distinct.
Beam hardening effect since the xray ct scan we are using a continuous xray, and it will continue to harden the radiation quality when the xray pass through the object. Beam hardening typically manifests itself as false density gradients in ct images of homogenous materials, termed cupping, and as streaks between highly. Sampledependent artifacts, on the other hand, are significantly more challenging as their effects can be reduced with ct techniques software corrections but are not always eliminated. Simulation of beam hardening in industrial ct with x corresponding author. Molthen department of biomedical engineering, marquette university, milwaukee, wisconsin 53201, and zablocki va medical center, milwaukee, wisconsin 53201 christopher a. Ct artifacts can be classified according to the underlying cause of the artifact. The algorithm employed a bayes classifier to identify beam hardening artifacts, followed by a partial correction of the attenuation map. The application of beam hardening correction for industrial xray computed tomography joseph j. Development and quantitative assessment of a beam hardening. Part of the biomedical engineering and bioengineering commons. Data consistency conditionbased beamhardening correction. The causal factors are the polyenergetic nature of xray beam used for imaging and the energy dependence of linear attenuation coefficient of the imaged material.
Reducing beam hardening artifacts has become an active research. Moreover, cera is designed as a flexible software platform which supports a broad range of cone beam and fan beam ct applications. With the recent development of novel reconstruction algorithms, we can not only image the object in. An introduction to ct scan image artifacts north star. Pdf the effect of beam hardening on resolution in xray. Application of a cardiacspecific beamhardening correction software algorithm is. The industry is facing new challenges in all markets, and with the continuous discovery of new vulnerabilities in more connected systems and sensors, customers need software systems to be secure, safe, and reliable outofthebox. The aim of this study was to develop a fast and accurate beam hardening correction method which can deal with beam hardening artifacts induced by multimaterials objects. A correction method for beam hardening, involving simple operations of the original polychromatic projection sinogram, is here presented based on the. Beam hardening correction with an iterative scheme using. An artifact reduction algorithm ara was developed to reduce metal artifacts in ctbased acpet.
Iterative beam hardening correction for multimaterial objects plos. In this paper, we propose an iterative beam hardening correction method that is applicable for the case with multiple materials. Those radiographs are used by a reconstruction software to obtain the. Quantitative reconstruction of cone beam xray computed tomography ct datasets requires accurate modeling of scatter, beam hardening, beam profile, and detector response. An iterative correction algorithm may be applied when images of bony regions are being reconstructed. Enabling threedimensional densitometric measurements. Hence, correction for beam hardening effect is of foremost importance and has been an active area of. Binary hardening is independent of compilers and involves the entire toolchain.
Beam hardening correction of multimaterial objects. Our equipment ranges from 50 200kv with beam powers up to 100kw. Nuclear engineering and technology programme, indian institute of technology, kanpur, india abstract. However, it is limited by the computer memory constraints in its application in multimaterial objects. Simulationaided investigation of beam hardening induced. Pdf iterative beam hardening correction for multimaterial. Bart s and the london school of dentistry, queen mary, university of london b. The scope of this paper is to present a comparative study of two methods for the correction of beam. Usa and also with the key laboratory of computer network and information. Ct artifacts are common and can occur for various reasons. This helps minimize blurring of the bonesoft tissue interface in brain scans,, fig 5 and also reduces the appearance of dark bands in nonhomogeneous cross sections,, fig 6. A modelbased image reconstruction algorithm with simultaneous. We develop and manufacture customerspecific electron beam systems for the following processes. Multimaterials beam hardening artifacts correction for.
Zhao is with the department of biomedical engineering, huazhong. When the object consists solely of a single material, the nonlinear beam hardening effect can be corrected using sinogram precorrection techniques. Yunsong zhao is employed by the shenzhen zhongke tianyue technology co. For a given sample, it may require experimenting with different kv and beam filtering combinations until adequate results are achieved. Simulation of beam hardening in industrial ct with x ray and.
The effect is conceptually similar to a highpass filter, in that only higher energy photons are left to contribute to the beam. Ara was implemented on phantom and patient 18 ffdg studies using a clinical petct scanner. Johnsonv i applied science laboratory, oe medical systems, milwaukee, wi 53201 zdepmtmcnt of diomedical engineering. These are either polynomial equations fit to an assumed background which is then removed via applying a correction factor, or are determined by automated proprietary. Beam hardening what is it and how to reduce it north.
An iterative approach to the beam hardening correction in cone beam ct jiang hsieh l, robert c. Numerous beam hardening correction methods have been developed, they include. Beam hardening is the phenomenon occurring when an xray beam comprised of polychromatic energies passes through an object, resulting in selective attenuation of lower energy photons. Asdip concrete is structural engineering software for design of concrete members. Method for beam hardening correction in quantitative computed. This software takes xray image data for a number of known samples, and fits them to a model of the beam hardening process which occurs when a broad. A simulationbased study on the influence of the xray spectrum on the performance of multimaterial beam hardening correction algorithms. Multimaterial beam hardening correctionmmbhc in computed tomography qiao yang, nicole maass, mengqiu tian, matthias elter, ingo schasiepen, andreas maier, and joachim hornegger abstractin computed tomography ct, the nonlinear attenuation characteristics of polychromatic xrays cause beam hardening artifacts in the reconstructed images.
A linearization beamhardening correction method for xray. High reproducibility and maximum productivity powerful, automated and highly digitized systems are the prerequisites for high productivity and quality in modern manufacturing processes. May 23, 2007 ct beam hardening artifacts near metal hip implants may erroneously enhance or diminish radiotracer uptake following ct attenuation correction ac of pet images. Nsis reconstruction software allow a series of sample images to be computed with a selection of beam hardening correction parameters, so you can select one with the most desired result for the full reconstruction. Manufacturers minimize beam hardening by using filtration, calibration correction, and beam hardening correction software. In this paper, we propose an iterative beam hardening correction method that is. Abstractbeam hardening is a well known effect in ct scanners that is cause by a combination of a broad polychromatic source xray spectrum and energydependent material attenuation. During translation, the motioncontrol system of the scanner repositions the. By assuming that the materials composing scanned object are known and that they are distinguishable by their linear attenuation coefficients at some given energy, the beam hardening correction problem is converted into a nonlinear system problem, which is then solved. The use of medical computed tomography ct systems for inspecting industrial materials and components such as ceramics, which have higher mass density and electron density than one encounters in medical applications, is subject to difficulties such as beam hardening and scattering. Julie skipper faculty researcher, nuclear engineering. The term beam hardening is used both to describe the appearance of an artefact in tomographic images and to describe the underlying principles. By studying the edge of a cylindrical object a value for the spatial resolution is obtained.
Thus, the penetrating power of xray will continue to increase. Pdf xray beamhardening bh produces artefacts in tomography that cause the reconstructed image to have incorrect attenuation values. Mcbride3 1the university of southampton, united kingdom. Iterative beam hardening correction for multimaterial objects. Some methods do not require prior knowledge of the material properties, for example 7, 8. Acquired process knowledge of both technologies laser hardening and laser cladding has been considered by erlas during configuration of the system components. The reason is that soft tissue path length as well as bone path length affect the extent of beam hardening simultaneously. Since the xray ct scan we are using a continuous xray, and it will continue to harden the radiation quality when the xray pass through the object. Obtaining accurate computerized tomography ct images is particularly critical for doctor to diagnose disease. The majority of sampledependent artifacts are caused by a phenomenon called beam hardening.
Beam hardening refers to the shift in mean energy of a polychromatic beam traversing matter, due to the predominant attenuation. Typically, commercial imaging systems use fast empirical corrections that are designed to reduce visible artifacts due to incomplete modeling of the image formation process. The goal of a beam hardening correction is then to correct the measurement so that it is as if it came from a system with a monoenergetic xray tube spectrum. This paper proposes a new method to correct beam hardening artifacts caused by the presence of metal in polychromatic xray computed tomography ct without degrading the intact anatomical images. The polynomial and the table correction were incorporated into a statistical model on which an iterative reconstruction algorithm was based. Sauer, member, ieee abstractbeam hardening is a well known effect in ct scanners that is cause by a combination of a broad polychromatic source xray spectrum and energydependent material attenuation. Oct 01, 2014 after your software has passed unit tests but before its delivered, a major goal is to flush out defects remaining that havent been caught in the unit tests. Ct, dimensional metrology, beam hardening correction. These artefacts affect the metal and surrounding nonmetal regions. As a result, a variety of methods have been proposed for correction. Thus, the attempt to utilize a single ct number range to identify and quantify the extent of a particular material can become problematic. Azadbakht, department of engineering, borujerd branch, islamic azad university, borujerd, iran. A modelling approach to be am hardening correction graham davis a, nitin jain b and james elliott a a. Beam hardening correction in iterative tomographic image.
Algorithm for xray scatter, beamhardening, and beam. Development of beam hardening correction algorithms for. An iterative approach to the beam hardening correction in. The ct simulation software models a realistic ct scanner brilliance 64.
Beam hardening caused by the polychromatic spectrum is an important problem in xray computed tomography xct. Existing bhc methods can be classified into hardware methods and software methods. Beamhardening correction methods for polychromatic xray ct. Multimaterial beam hardening correctionmmbhc in computed. How to design continuous beams using asdip concrete. As manufacturers of electron beam welders and vacuum furnaces, at cambridge vacuum engineering cve we design and build process solutions. In order to improve the image quality, beam hardening correction bhc methods have been studied even since the invention of the xray ct 2, 3. Beam hardening correction with an iterative scheme using an. During beam hardening, the mean energy of the xray beam increases, and dense metal samples can cause severe beam hardening due to reasonably high atomic number as compared to soft tissues.
Beamhardening artifacts confound dynamic volume ct assessment of. Current software based scatter correction methods include monte carlo simulation 2 and statistical modeling 3. Artifacts and partialvolume effects utct university. In order to obtain the approximately optimal parameters for the method, we reconstruct images with different parameters that are distributed uniformly in a large interval, and then choose the parameters that have the best correction result. A software method is mainly linearization correction.
Fast iterative beam hardening correction based on frequency. One of the original software beamhardening correction methods, and still the most common for industrial ct systems, is to use a function that attempts to transform the polychromatic attenuation data into equivalent monochromatic data, an operation referred to as linearization herman, 1979. The most commonly encountered artifact in ct scanning is beam hardening, which. Beamhardening artefact definition of beamhardening. With increase in length of propagation of beam in the imaged object, lower energy photons in the projected beam. Cera supports the latest technology in ct reconstruction both in terms of innovative algorithms and hardware acceleration.
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