Industrial CT System Research Articles

Simulated and experimental evaluation of the accuracy of twin robotic CT systems

Conventional industrial X-Ray CT systems are limited in their movement because of their limited degrees of freedom and overall design. Equipping CT with two industrial robotic arms, e.g. for manipulating source and detector, overcomes this limitation. Industrial robots are less restricted in the positioning and orientation of their X-ray tools than comparable industrial CT systems, making them flexible manipulators. However, their absolute positioning accuracy is usually below the minimum requirement for use in computed tomography. This paper proposes a calibration method with a variable, low-cost calibration body that allows pose correction of arbitrary projection geometries. The results from a twin robotic CT system will be evaluated via simulated projection data and actual experimental computer tomographic reconstruction.

Image Enhancement in Lens-Coupled Detectors for industrial CT systems

These days, lens-coupled detectors have been taken into consideration due to their cost effectiveness, but they have some disadvantages relative to other detectors such as flat panel detectors. Meanwhile, white spot noise and light spreading due to optical distance, will result in reduction of the quality of the reconstructed object in computed tomography applications. In this paper, due to limited power of classical methods, to fix these dysfunctions, we have learned a Neural network for improvement of the images.

Development and application of high-performance cone-beam industrial X-ray CT system

Development and application of high-performance cone-beam industrial X-ray CT system

Spatial resolution measurement of industrial CT system based on equal diameter circumscribed circle phantom

Spatial resolution measurement of industrial CT system based on equal diameter circumscribed circle phantom

Shape prior metal artefact reduction algorithm for industrial 3D cone beam CT

ABSTRACT Metal artefact reduction has become a challenging issue for practical X-ray CT applications since metal artefacts severely cause contrast degradation and the misinterpretation of information about the property and structure of a scanned object. In this paper, we propose a methodology to reduce metal artefacts in a three-dimensional industrial cone beam CT system. We develop a registration technique managing the three dimensional data in order to find accurate segmentation regions needed for the proposed algorithm. Through various simulations and experiments, we verify that the proposed algorithm reduces metal artefacts successfully.

Study on Influence of Different Gamma-ray Energy on Images of an Industrial CT System

Gamma transmission computed tomography is a powerful imaging techniques that provide a cross-sectional view or a volumetric view of the interior of an object. Therefore, reveal structural information of an object as if it had been cut open for viewing. By utilizing the properties of gamma-ray attenuation, images were reconstructed from photon counting data by gamma-ray sensor. Information revealed on these images depends greatly on resolution of the reconstructed images. In this study, the effect of gamma-ray energy used on a portable CT images is studied. Lab sample of four different material densities were used with three different gamma-ray sources namely, Am-241, Ba-133 and Cs-137 to study the effect of energy on the reconstructed images. The best reconstructed image that describes the structure of the sample used in this study is from Ba-133 with energy of 356 keV. The results provide information on suitability of the energy used for the range of material density use in this study.

Beam Hardening Correction Using Cone Beam Consistency Conditions.

The polychromatic X-ray spectrum and the energy-dependent attenuation coefficient of materials cause beam hardening artifacts in CT reconstructed volumes. These artifacts appear as cupping and streak artifacts depending on the material composition and the geometry of the imaged object. CT scanners employ projection linearization to transform polychromatic attenuation to monochromatic attenuation using a polynomial model. Polynomial coefficients are computed during calibration or using prior information such as X-ray spectrum and attenuation properties of the materials. In this paper, we are presenting a novel method to correct beam hardening artifacts by enforcing cone beam consistency conditions on the projection data. We used consistency conditions derived from Grangeat's fundamental relation between cone beam projection data and 3-D Radon transform. The optimal polynomial coefficients for artifact reduction are iteratively estimated by minimizing the inconsistency of a set of projection pairs. The results from simulated and real datasets show the visible reduction of artifacts. Our studies also demonstrate the robustness of the algorithm when the projections are perturbed with other physical measurement and geometrical errors. The proposed method requires neither calibration nor prior information like X-ray spectrum, attenuation properties of the materials and detector response. The algorithm can be used for beam hardening correction in clinical, pre-clinical, and industrial CT systems.

Synchronous scanning mode of industrial computed tomography for multiple objects test

When testing small size and high density objects with a broad field-of-view (FOV) industrial CT system, multiple objects are always assembled evenly onto the turntable for detecting to improve test efficiency. However, the maximum X-ray's penetrating path through the materials increases, which means the CT system should collocate with a high energy X-ray source and wide-dynamic range detectors to complete the CT scanning. In this study, we proposed and tested a novel and efficient CT scanning method based on linear-arrangement and synchronous-rotating multi-turntables without enhancing the energy of X-ray source and wide-dynamic range of detectors for the CT system. With this modality, multiple objects are assembled onto multiple synchronous-rotating turntables respectively, and X-rays within the FOV merely penetrate one single object when scanning. The corresponding filtered back projection algorithm for image reconstruction is deduced. The computer simulation and experimental results verified the feasibility of this novel method and the scanning time was reduced to 5-8 minutes when completing the scanning of 3 to 5 group objects.

Swinging multi-source industrial CT systems for aperiodic dynamic imaging.

The goal of this paper is to develop a new architecture for industrial computed tomography (ICT) aiming at dynamically imaging an aperiodic changing object. We propose a data acquisition approach with multiple x-ray source/detector pairs targeting a continuously changeable object with corresponding timeframes. In this named swinging multi-source CT (SMCT) structure, each source and its associated detector swing forth and back within a certain angle for CT scanning. In the SMCT system design, we utilize a circular journal bearing based setup to replace the normal CT slip ring by weakening the scanning speed requirement. Inspired by the prior image constrained compressed sensing (PICCS) algorithm, we apply a modified PICCS algorithm for the SMCT (SM-PICCS). Our numerical simulation and realistic specimen experiment studies demonstrate the feasibility of the proposed approach.

Energy Spectrum Measurement of High Power and High Energy (6 and 9 MeV) Pulsed X-ray Source for Industrial Use

Background: Industrial X-ray CT system is normally applied to non-destructive testing (NDT) for industrial product made from metal. Furthermore there are some special CT systems, which have an ability to inspect nuclear fuel assemblies or rocket motors, using high power and high energy (more than 6 MeV) pulsed X-ray source. In these case, pulsed X-ray are produced by the electron linear accelerator, and a huge number of photons with a wide energy spectrum are produced within a very short period. Consequently, it is difficult to measure the X-ray energy spectrum for such accelerator-based X-ray sources using simple spectrometry. Due to this difficulty, unexpected images and artifacts which lead to incorrect density information and dimensions of specimens cannot be avoided in CT images. For getting highly precise CT images, it is important to know the precise energy spectrum of emitted X-rays. Materials and Methods: In order to realize it we investigated a new approach utilizing the Bayesian estimation method combined with an attenuation curve measurement using step shaped attenuation material. This method was validated by precise measurement of energy spectrum from a 1 MeV electron accelerator. In this study, to extend the applicable X-ray energy range we tried to measure energy spectra of X-ray sources from 6 and 9 MeV linear accelerators by using the recently developed method. Results and Discussion: In this study, an attenuation curves are measured by using a step-shaped attenuation materials of aluminum and steel individually, and the each X-ray spectrum is reconstructed from the measured attenuation curve by the spectrum type Bayesian estimation method. Conclusion: The obtained result shows good agreement with simulated spectra, and the presently developed technique is adaptable for high energy X-ray source more than 6 MeV.

A THIRD GENERATION GAMMA-RAY INDUSTRIAL COMPUTED TOMOGRAPHY SYSTEMS FOR PIPELINE INSPECTION

This paper introduces an industrial CT system of compact fan beam configuration which was designed and fabricated by Centre for Applications of Nuclear Technique in Industry (CANTI) for inspecting pipe and small scale industrial equipment. The system utilizes a Cs-137 or Se-75 isotopic source. The source is contained in a fan beam collimator made of lead. The slit size of the source collimator is 10 mm in width in the axial direction and the opening angle of the fan beam is 900. Twelve ½ inch x 1 inch NaI(Tl) scintillation detectors and multiple SCAs (Single Chanel Analyzer) are used to set up the detection system. Filtered Back Projection (FBP) and Expectation Maximization (EM) algorithms were used for reconstruction of CT images. Having compact configuration of third generation CT, the size of gantry is 900 mm which enable to scan an object with diameter of 600 mm whereas the detector arc in a conventional third generation configuration must be at least 1200mm to cover the same object.

Improve spatial resolution by Modeling Finite Focal Spot (MFFS) for industrial CT reconstruction.

The finite focal spot is one of the major limitations of the high spatial resolution CT, especially to the high-energy industrial CT system with a macro-focus x-ray source. In this paper, we propose an efficient reconstruction framework through finite focal spot size based projection modeling to improve the spatial resolution of current industrial CT system, and demonstrate the superior performance of this method. First of all, the blurred projection produced by a finite size source is modeled as the integral ideal projection of a given point source over the finite focal spot support. Under the model discretization, the approximate linear equivalence relation between the actual finite focus model and the ideal point source model is established. Then a projection recovery method with this relationship is presented to recover the projection of the finer focal spot from the blurred projection. Finally, a high-spatial resolution image can be reconstructed from the recovered projections using the standard Filtered Back-Projection (FBP) algorithm. Furthermore the noise in the reconstructed image with different model parameters is studied and a difference image based fusion method is presented for the further suppression of the noise caused by the projection analysis processing. Both numerical simulations and real experiments have shown that the proposed reconstruction framework with the outstanding performance and efficiency characteristics can significantly enhance the spatial resolutions of current high-energy industrial CT systems.

Beam hardening correction for X-ray computed tomography of heterogeneous natural materials

We present a new method for correcting beam hardening artifacts in polychromatic X-ray CT data. 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. However, determining optimal coefficients for the transform equation is not straightforward, especially if the material is not well known or characterized, as is the usual case when imaging geological materials. Our method uses an iterative optimization algorithm to find a generalized spline-interpolated transform that minimizes artifacts as defined by an expert user. This generality accesses a richer set of linearization functions that may better accommodate the effects of multiple materials in heterogeneous samples. When multiple materials are present in the scan field, there is no single optimal correction, and the solution can vary depending on which aspects of the beam-hardening and other image artifacts the user wants to minimize. For example, the correction can be optimized to maximize the fidelity of the object outline for solid model creation rather than simply to minimize variation of CT numbers within the material. We demonstrate our method on a range of specimens of varying difficulty and complexity, with consistently positive results.

A study of metal artefact reduction for industrial X-ray CT system with limited radiation energy

A study of metal artefact reduction for industrial X-ray CT system with limited radiation energy

反復的位相回復法によるMissing Cone問題における欠落データ補間法

A conical CT system was used for the industrial X-ray CT system on this paper. It is known that this system has a missing cone problem, which causes a growth of image. We used an iterative phase retrieval algorithm as a proposal to solve this problem. We confirmed that this algorithm can recover a data of low frequency such as the approximate outline of the object. In addition, we tried to make a new constrain, boundary condition, which is implemented along the boundary of the missing cone. Through this search, it was found out that this algorithm offered the access to reducing the relative-error-rate by approximate 80%.

Study & Manufacture RM of Industrial CT System

This paper introduces a method of studied and manufactured reference material for calibrating magnification of computed tomography system. The measurement procedure and certified value method of the reference material were also described. Moreover, uncertainty of measurement was evaluated in this paper, by which a state level of confidence was accompanied. Finally one example of application of the reference material was described. We thought that reference material of CT system will update its function and develop its applied field.

Measurement of the spatial resolution and the relative density resolution in an industrial cone-beam micro computed tomography system

The spatial resolution and the relative density resolution are the two most critical indicators in CT system. The method recommended in the ASTM E1695-95 and GJB 5311-2004 is only suitable to the fan-beam CT system. In this paper, for industrial cone-beam micro CT system, we will adopt the edge response function (ERF) created by the step edges of a steel ball to measure the system 3D PSF and MTF. To describe the contrast discrimination function more accurately, we will first propose to extend the two-dimensional measurement region to the three-dimensional space. Our experimental spatial resolution is (55.56±0.56) lp/mm and the relative density resolution is 1% within 300 μm×300 μm×300 μm according to the 3σ rule.

Study on CT Image Reconstruction Applications in Industry

We require high-precision measurement method in the modern industrial production. The method of measurement of industrial CT images is a good choice now. The face of some of the drawbacks of the current industrial CT images, this paper is starting from the study of industrial CT system structure and algorithm flowchart. We focus on the algorithm of Zernike moments, and on the basis of the algorithm itself, it carried out a number of improvements to improve the measurement accuracy of the industrial CT algorithm. Then design a set of industrial CT measurement method of intelligent software solutions, the specific design method and the structure model diagram will be given.

Forming Mechanism and Correction of CT Image Artifacts Caused by the Errors of Three System Parameters

We know that three system parameters, a center of X-ray source, an isocenter, and a center of linear detectors, are very difficult to be calibrated in industrial CT system. So there are often the offset of an isocenter and the deflection of linear detectors. When still using the FBP (filtered backprojection) algorithm under this condition, CT image artifacts will happen and then can seriously affect test results. In this paper, we give the appearances and forming mechanism of these artifacts and propose the reconstruction algorithm including a deflection angle of linear detectors. The numerical experiments with simulated data have validated that our propose algorithm can correct CT images artifacts without data rebinning.

Combination of Coal and Rock Uniaxial Compression Test Image Processing of CT

The use of industrial CT systems, and special loading equipment, combination of coal and rock under uniaxial compression load test real-time CT scan obtained at different loads under various stages of the CT images. Using digital image processing technology to coal combination of the CT image gray stretch and pseudo-color enhancement to improve image contrast, highlighting the cracks and pores of the edge information. To establish a combination of coal to the coal from the rock micro-crack interaction and its associated macro-deformation, further study coal - roof and floor damage and the impact of mechanical systems to the mechanism of pressure to provide experimental basis.