Development and quantitative assessment of a beam hardening. 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. Julie skipper faculty researcher, nuclear engineering. The phenomenon of xray beam hardening bh has significant impact on preclinical microct imaging systems. 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 artifacts are highly undesirable for a medical diagnosis, because details in the reconstructed image are severely disturbed or completely lost. Data consistency conditionbased beamhardening correction. A level set method for cupping artifact correction in cone.
The algorithm employed a bayes classifier to identify beam hardening artifacts, followed by a partial correction of the attenuation map. The ct simulation software models a realistic ct scanner brilliance 64. Pdf iterative beam hardening correction for multimaterial. What does hardening phase mean in terms of software. 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. Polychromatic ct data improvement with oneparameter power.
Characterization and correction of beamhardening artifacts during. Ct artifacts are common and can occur for various reasons. Enabling threedimensional densitometric measurements. Iterative beam hardening correction for multimaterial objects plos. Exploratory research into reduction of scatter and beam. Metal artifact reduction for polychromatic xray ct based on. The reason is that soft tissue path length as well as bone path length affect the extent of beam hardening simultaneously. We present a new method for correcting beam hardening artifacts in polychromatic xray ct data.
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. 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. Electron beam systems for welding, drilling and hardening. Beam hardening correction of multimaterial objects. Molthen department of biomedical engineering, marquette university, milwaukee, wisconsin 53201, and zablocki va medical center, milwaukee, wisconsin 53201 christopher a. The effect is conceptually similar to a highpass filter, in t.
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. 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. We derive the polynomial beam hardening correction, a method described in more detail elsewhere. An iterative correction algorithm may be applied when images of bony regions are being reconstructed. Additionally, form errors hinder dimensional evaluation. 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. 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. 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. 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.
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. 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. 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 typically manifests itself as false density gradients in ct images of homogenous materials, termed cupping, and as streaks between highly. Pdf the effect of beam hardening on resolution in xray. A correction method for beam hardening, involving simple operations of the original polychromatic projection sinogram, is here presented based on the. As a result, a variety of methods have been proposed for correction. Beam hardening correction and its influence on the. An iterative approach to the beam hardening correction in cone beam ct jiang hsieh l, robert c. Artifacts and partialvolume effects utct university. Reducing beam hardening artifacts has become an active research. High reproducibility and maximum productivity powerful, automated and highly digitized systems are the prerequisites for high productivity and quality in modern manufacturing processes.
Analysis and artifact correction for volume correlation measurements. This is the basis for short reconstruction times and excellent image quality alike. Reducing beam hardening effects and metal artefacts using. The influence of beam hardening corrections are studied in section 6.
In this paper, we propose an iterative beam hardening correction method that is. The majority of sampledependent artifacts are caused by a phenomenon called beam hardening. Highfidelity artifact correction for conebeam ct imaging. Optical engineering 507, 076501 july 2011 data consistency conditionbased beamhardening correction shaojie tang xian university of posts and telecommunications. An iterative approach to the beam hardening correction in. Azadbakht, department of engineering, borujerd branch, islamic azad university, borujerd, iran. Part of the biomedical engineering and bioengineering commons. The brabant method compensates the hardening of xray beam by introducing two parameters in the forward projection process of the iteration. An improved beam hardening correction technique will provide qct measurements and ct images with improved accuracy. L study conceptsstudy design or data acquisition or data. Typically, commercial imaging systems use fast empirical corrections that are designed to reduce visible artifacts due to incomplete modeling of the image formation process. Multimaterials beam hardening artifacts correction for. Metal artifacts in computed tomography for radiation. Johnsonv i applied science laboratory, oe medical systems, milwaukee, wi 53201 zdepmtmcnt of diomedical engineering.
In the past, many studies have been conducted to combat image artifacts induced by beam hardening. A simulationbased study on the influence of the xray spectrum on the performance of multimaterial beam hardening correction algorithms. 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. Cera ct reconstruction and artifact reduction siemens. Nuclear engineering and technology programme, indian institute of technology, kanpur, india abstract. 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. Beamhardening artefact definition of beamhardening. Knowledge of these artifacts is important because they can mimic pathology e.
In this paper, we present an iterative beam hardening correction approach for cone beam ct. Beamhardening correction method based on original sinogram. Ct artifacts can be classified according to the underlying cause of the artifact. 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. The first proposed algorithm employs a statistical learning. These artefacts affect the metal and surrounding nonmetal regions.
The bonecorrection method has been widely adopted to compensate for beam hardening artifacts. Beam hardening correction with an iterative scheme using. 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. Beamhardening correction methods for polychromatic xray. The application of beam hardening correction for industrial x.
The term beam hardening is used both to describe the appearance of an artefact in tomographic images and to describe the underlying principles. The fast mc scatter estimation combines gpu acceleration, variance reduction, and simulation with a low number of photon histories and reduced number of projection angles sparse mc augmented by kernel denoising to yield a runtime of 4min per scan. 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. Machinelearningbased nonlinear decomposition of ct images. Those radiographs are used by a reconstruction software to obtain the. 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. 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. An introduction to ct scan image artifacts north star. For example, one binary hardening technique is to detect potential buffer overflows and to substitute the existing code with safer code. The measurement hardware and software used for all measurements reported in. 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. Development of beam hardening correction algorithms for. Nov 27, 2001 there exists a need in the art of ct imaging and qct for an improved method of beam hardening 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.
Obtaining accurate computerized tomography ct images is particularly critical for doctor to diagnose disease. Multimaterial beam hardening correctionmmbhc in computed. A modelbased image reconstruction algorithm with simultaneous. Simulationaided investigation of beam hardening induced. 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. Ct, dimensional metrology, beam hardening correction. Beam hardening what is it and how to reduce it north star.
Cera supports the latest technology in ct reconstruction both in terms of innovative algorithms and hardware acceleration. An artifact reduction algorithm ara was developed to reduce metal artifacts in ctbased acpet. In ct images of objects made of several materials with significant different attenuation characteristics these effects are even more distinct. Moreover, cera is designed as a flexible software platform which supports a broad range of cone beam and fan beam ct applications. 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. 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. Asdip concrete software includes the design of multispan continuous beams based on the latest aci 318 provisions. Some methods do not require prior knowledge of the material properties, for example 7, 8. Binary hardening is a security technique in which binary files are analyzed and modified to protect against common exploits. Accordingly, it is a primary object of the present invention to provide an improved. Numerous beam hardening correction methods have been developed, they include.
Usa and also with the key laboratory of computer network and information. Bart s and the london school of dentistry, queen mary, university of london b. Application of a cardiacspecific beamhardening correction software algorithm is. Zhao is with the department of biomedical engineering, huazhong. Beamhardening correction methods for polychromatic xray ct. 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. With the recent development of novel reconstruction algorithms, we can not only image the object in. Beam hardening refers to the shift in mean energy of a polychromatic beam traversing matter, due to the predominant attenuation. The effect is conceptually similar to a highpass filter, in that only higher energy photons are left to contribute to the beam. With more than 60 years experience, we manufacture these systems at our headquarters located in cambridge uk. Pdf xray beamhardening bh produces artefacts in tomography that cause the reconstructed image to have incorrect attenuation values.
Beam hardening correction for xray computed tomography of. Polychromatic xray beams are used by ct scanners and the lower energy photons are more easily absorbed by matter, especially the. Thus, the attempt to utilize a single ct number range to identify and quantify the extent of a particular material can become problematic. Beam hardening what is it and how to reduce it north. When the object consists solely of a single material, the nonlinear beam hardening effect can be corrected using sinogram precorrection techniques. The scope of this paper is to present a comparative study of two methods for the correction of beam. Existence of beam hardening artifact will degrade ct images, or even affects the applicability of the ct images. The polynomial and the table correction were incorporated into a statistical model on which an iterative reconstruction algorithm was based. Simulation of beam hardening in industrial ct with x ray and. Mcbride3 1the university of southampton, united kingdom. Existing bhc methods can be classified into hardware methods and software methods. In todays connected world, software application resiliency takes an increasingly predominant role. 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.
During translation, the motioncontrol system of the scanner repositions the. Hence, correction for beam hardening effect is of foremost importance and has been an active area of. Fast iterative beam hardening correction based on frequency. Method for beam hardening correction in quantitative computed. The method described in this paper allows the correction of beam hardening artifacts in multimaterial objects. By studying the edge of a cylindrical object a value for the spatial resolution is obtained. 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. Beam hardening correction with an iterative scheme using an. A linearization beamhardening correction method for xray. Yunsong zhao is employed by the shenzhen zhongke tianyue technology co. Beam hardening correction in iterative tomographic image.
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. 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. Binary hardening is independent of compilers and involves the entire toolchain. Manufacturers minimize beam hardening by using filtration, calibration correction, and beam hardening correction software. Image b is the result of a software correction of the ring artifacts in a. The application of beam hardening correction for industrial xray computed tomography joseph j. 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. Beam hardening caused by the polychromatic spectrum is an important problem in xray computed tomography xct. Beam hardening bh occurs when polychromatic radiation is. In this paper, we propose an iterative beam hardening correction method that is applicable for the case with multiple materials. Pdf software xray beam hardening correction of cylindrical.
Acquired process knowledge of both technologies laser hardening and laser cladding has been considered by erlas during configuration of the system components. Iterative beam hardening correction for multimaterial objects. 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. As a result, errors are present in the acquired line integrals or measurements of the attenuation coefficients of the scanned object. 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. 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.
We develop and manufacture customerspecific electron beam systems for the following processes. The most commonly encountered artifact in ct scanning is beam hardening, which. 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. Beam hardening effects are visible in the form of streak artefacts and cupping effects. Beam hardening can also be correctedreduced during reconstruction. Tang et al data consistency conditionbased beamhardening correction fig. Many commercially available software packages that are coupled with xray tomography systems offer a suite of options to apply prereconstruction beam hardening corrections. How to design continuous beams using asdip concrete. Metal artifact reduction for polychromatic xray ct based on a beam hardening corrector. Our equipment ranges from 50 200kv with beam powers up to 100kw.
Quantitative reconstruction of cone beam xray computed tomography ct datasets requires accurate modeling of scatter, beam hardening, beam profile, and detector response. Toward comprehensive industrial computed tomography image. Following is an overview of the steps required to design continuous beams using asdip concrete. Bouman are with the school of electrical and computer. Engineering, purdue university, west lafayette, in 479070501 usa email. A comparative study of two methods for the correction of beam. 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. Beamhardening artifacts confound dynamic volume ct assessment of. A modelling approach to be am hardening correction graham davis a, nitin jain b and james elliott a a. 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. Ara was implemented on phantom and patient 18 ffdg studies using a clinical petct scanner. This function is typically an exponential or polynomial of undetermined degree. 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.
It leads to various artifacts in reconstruction images and reduces image quality. As manufacturers of electron beam welders and vacuum furnaces, at cambridge vacuum engineering cve we design and build process solutions. However, it is limited by the computer memory constraints in its application in multimaterial objects. Simulation of beam hardening in industrial ct with x corresponding author. Thus, the penetrating power of xray will continue to. Data consistency conditionbased beamhardening correction article pdf available in optical engineering 507 july 2011 with 363 reads how we measure reads. 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. With increase in length of propagation of beam in the imaged object, lower energy photons in the projected beam. 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. Flowchart for frequency splitting accelerated iterative beam hardening correction. Current software based scatter correction methods include monte carlo simulation 2 and statistical modeling 3.
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. Asdip concrete is structural engineering software for design of concrete members. A method for simultaneous image reconstruction and beam. Algorithm for xray scatter, beamhardening, 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. A correction table with both bone and tissue dimension was then developed. This function is typically an exponential or polynomial of undetermined degree or coefficient values. However, as a consequence of the polychromatic source used in microct, beam hardening will occur which has the effect of enhancing the edges of the objects in the reconstruction images.
For a given sample, it may require experimenting with different kv and beam filtering combinations until adequate results are achieved. Artifacts and partialvolume effects utct university of texas. Thus, the penetrating power of xray will continue to increase. A software method is mainly linearization correction. In this work, we present an iterative scheme which signi. The application for electron beam hardening lies in treating surfaces with a hardening depth ranging from 0.
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