scholarly journals Reducing metal artifacts by restricting negative pixels

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Gengsheng L. Zeng ◽  
Megan Zeng
Keyword(s):  
Computed Tomography ◽  
Objective Function ◽  
Ct Scans ◽  
Filtered Backprojection ◽  
Beam Hardening ◽  
Metal Artifacts ◽  
X Ray ◽  
X Ray Computed ◽  
Set Up ◽  
True Values

AbstractWhen the object contains metals, its x-ray computed tomography (CT) images are normally affected by streaking artifacts. These artifacts are mainly caused by the x-ray beam hardening effects, which deviate the measurements from their true values. One interesting observation of the metal artifacts is that certain regions of the metal artifacts often appear as negative pixel values. Our novel idea in this paper is to set up an objective function that restricts the negative pixel values in the image. We must point out that the naïve idea of setting the negative pixel values in the reconstructed image to zero does not give the same result. This paper proposes an iterative algorithm to optimize this objective function, and the unknowns are the metal affected projections. Once the metal affected projections are estimated, the filtered backprojection algorithm is used to reconstruct the final image. This paper applies the proposed algorithm to some airport bag CT scans. The bags all contain unknown metallic objects. The metal artifacts are effectively reduced by the proposed algorithm.

X-RAY TOMOGRAPHY STUDIES OF PREHISTORIC CERAMIC ARTIFACTS

2014 ◽  
Vol 27 ◽  
pp. 1460135
Author(s):  
CARMEN PAVEL ◽  
FLORIN CONSTANTIN ◽  
COSMIN IOAN SUCIU ◽  
ROXANA BUGOI
Keyword(s):  
Computed Tomography ◽  
Cultural Heritage ◽  
Nuclear Physics ◽  
Structural Information ◽  
Ct Scans ◽  
Visual Examination ◽  
X Ray ◽  
X Ray Computed ◽  
Internal Configuration ◽  
Non Destructive

X-ray Computed Tomography (CT) is a powerful non-destructive technique that can yield interesting structural information not discernible through visual examination only. This paper presents the results of the CT scans of four objects belonging to the Romanian cultural heritage attributed to the Vinča, Cucuteni and Cruceni-Belegiš cultures. The study was performed with an X-ray tomographic device developed at the Department for Applied Nuclear Physics from Horia Hulubei National Institute for Nuclear Physics and Engineering in Măgurele, Romania. This apparatus was specially designed for archaeometric studies of low-Z artifacts: ceramic, wood, bone. The tomographic investigations revealed the internal configuration of the objects and provided information about the degree to which the previous manipulations affected the archaeological items. Based on the X-ray images resulting from the CT scans, hints about the techniques used in the manufacturing of the artifacts were obtained, as well as some indications useful for conservation/restoration purposes.

scholarly journals Fiber orientation quantification utilizing X-ray micro-computed tomography

2020 ◽  
pp. 002199832096255
Author(s):  
Jennifer M Sietins ◽  
Jessica C Sun ◽  
Daniel B Knorr Jr
Keyword(s):  
Computed Tomography ◽  
Fiber Orientation ◽  
Mechanical Performance ◽  
Ct Scans ◽  
Micro Computed Tomography ◽  
Orientation Data ◽  
Orientation Analysis ◽  
X Ray ◽  
Software Analysis ◽  
X Ray Computed

It is well known that the mechanical performance of composite materials is highly dependent on the fiber orientation. Several techniques have historically been used to quantify fiber orientation experimentally. Newer methods have involved 3 D X-ray computed tomography (CT) scans due to the high resolution that is now achievable within a laboratory setting. The accuracy of the analysis, however, is a function of the resulting scan image quality and the specific parameters influencing the resulting orientation analysis. This report summarizes a methodology to quantify fiber orientation from 3 D CT scans. Optimal scanning parameters are presented taking into account both the necessary resolution, geometric unsharpness, and the scan volume size. The influence of varied software analysis parameters and their effects on the resulting orientation data is discussed. The selection of software analysis parameters was independently validated with optical microscopy on a sample with only two fibers. Lastly, the orientation analysis was applied to a 0/+45/−45/90 composite to demonstrate this technique on a larger scale.

scholarly journals OBSERVATIONS ON THE PERFORMANCE OF X-RAY COMPUTED TOMOGRAPHY FOR DIMENSIONAL METROLOGY

2016 ◽  
Vol XLI-B5 ◽  
pp. 25-31
Author(s):  
H. C. Corcoran ◽  
S. B. Brown ◽  
S. Robson ◽  
R. D. Speller ◽  
M. B. McCarthy
Keyword(s):  
Computed Tomography ◽  
Reverse Engineering ◽  
X Rays ◽  
Dimensional Metrology ◽  
Beam Hardening ◽  
X Ray ◽  
Accuracy And Precision ◽  
Dimensional Measurements ◽  
X Ray Computed

X-ray computed tomography (XCT) is a rising technology within many industries and sectors with a demand for dimensional metrology, defect, void analysis and reverse engineering. There are many variables that can affect the dimensional metrology of objects imaged using XCT, this paper focusses on the effects of beam hardening due to the orientation of the workpiece, in this case a holeplate, and the volume of material the X-rays travel through. Measurements discussed include unidirectional and bidirectional dimensions, radii of cylinders, fit point deviations of the fitted shapes and cylindricity. Results indicate that accuracy and precision of these dimensional measurements are affected in varying amounts, both by the amount of material the X-rays have travelled through and the orientation of the object.

Very Low-Intensity Throughput X-Ray Computed Tomography of a Cast FeMnAl Steel Alloy

2020 ◽  
Vol 3 (4) ◽  
Author(s):  
William H. Green ◽  
Bryan A. Cheeseman ◽  
Daniel Field ◽  
Krista R. Limmer
Keyword(s):  
Computed Tomography ◽  
Detector Response ◽  
Steel Alloy ◽  
Material Technology ◽  
X Ray ◽  
Low Intensity ◽  
Combat Vehicle ◽  
X Ray Computed ◽  
Set Up ◽  
Iron Manganese

Abstract The X-ray computed tomography (XCT) technique is a widely applicable and powerful non-destructive inspection modality for evaluation and analysis of geometrical and physical characteristics of materials, especially internal structures and features. XCT is applicable to metals, ceramics, plastics, and polymer and mixed composites, as well as components and materiel. The Army Research Laboratory (ARL) and its partners are currently investigating the use of cast iron-manganese-aluminum (FeMnAl) steel alloy material in support of weight reduction initiatives in Army Development Programs. Steel alloy FeMnAl has been identified as a key enabling material technology to reduce the weight in ground combat vehicle systems. A set of FeMnAl blocks each approximately 50.8 mm (2 in.) thick by 76.2 mm (3 in.) wide by 76.2 mm (3 in.) long, which had been sectioned from an industrially cast ingot (∼12,000 lbs.), were individually scanned by XCT using a conventional 450 kV X-ray source and a solid-state flat panel detector. Mainly due to the thickness of the blocks, as well as a desire to keep geometric unsharpness relatively small which affected overall scan geometry (set up), the scans had a very low response at the detector through the FeMnAl blocks. With the calibrated detector response through air (i.e., around a block) at 85–90% the response through the block was only 5–10%. The XCT scanning parameters and overall protocol used to mitigate the very low-intensity throughput and achieve acceptable scan image results will be discussed. Image processing (IP) methods used to segment porosity features in the FeMnAl blocks will also be discussed.

X-ray computed tomography: Practical evaluation of beam hardening in iron ore samples

2019 ◽  
Vol 131 ◽  
pp. 206-215 ◽  
Author(s):  
Lunga Cleartone Bam ◽  
Jodie Ann Miller ◽  
Megan Becker ◽  
Ian James Basson
Keyword(s):  
Computed Tomography ◽  
Iron Ore ◽  
Beam Hardening ◽  
X Ray ◽  
Practical Evaluation ◽  
X Ray Computed
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