Reduction of metal artifacts: beam hardening and photon starvation effects

2014 ◽  
Author(s):  
Girijesh K. Yadava ◽  
Debashish Pal ◽  
Jiang Hsieh
Keyword(s):  
Beam Hardening ◽  
Metal Artifacts ◽  
Starvation Effects

scholarly journals Contrast Enhancement Method Based on Gray and Its Distance Double-Weighting Histogram Equalization for 3D CT Images of PCBs

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Lei Zeng ◽  
Bin Yan ◽  
Weidong Wang
Keyword(s):  
Printed Circuit Boards ◽  
Histogram Equalization ◽  
Ct Images ◽  
3D Ct ◽  
Circuit Boards ◽  
Beam Hardening ◽  
Metal Artifacts ◽  
Low Contrast ◽  
Image Histogram ◽  
Enhancement Method

Cone beam computed tomography (CBCT) is a new detection method for 3D nondestructive testing of printed circuit boards (PCBs). However, the obtained 3D image of PCBs exhibits low contrast because of several factors, such as the occurrence of metal artifacts and beam hardening, during the process of CBCT imaging. Histogram equalization (HE) algorithms cannot effectively extend the gray difference between a substrate and a metal in 3D CT images of PCBs, and the reinforcing effects are insignificant. To address this shortcoming, this study proposes an image enhancement algorithm based on gray and its distance double-weighting HE. Considering the characteristics of 3D CT images of PCBs, the proposed algorithm uses gray and its distance double-weighting strategy to change the form of the original image histogram distribution, suppresses the grayscale of a nonmetallic substrate, and expands the grayscale of wires and other metals. The proposed algorithm also enhances the gray difference between a substrate and a metal and highlights metallic materials. The proposed algorithm can enhance the gray value of wires and other metals in 3D CT images of PCBs. It applies enhancement strategies of changing gray and its distance double-weighting mechanism to adapt to this particular purpose. The flexibility and advantages of the proposed algorithm are confirmed by analyses and experimental results.

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.

Adrenalectomy eliminates both fiber-type differences and starvation effects on denervated muscle

1988 ◽  
Vol 255 (6) ◽  
pp. E850-E856 ◽  
Author(s):  
R. R. Almon ◽  
D. C. Dubois
Keyword(s):  
Muscle Mass ◽  
Extensor Digitorum Longus ◽  
Fiber Type ◽  
Sprague Dawley ◽  
Denervated Muscle ◽  
Adrenalectomized Animal ◽  
Sprague Dawley Rats ◽  
Starvation Effects ◽  
The Difference ◽  
Denervated Muscles

This report describes changes in muscle mass of innervated and denervated pairs of muscles taken from intact and adrenalectomized 250-g male Sprague-Dawley rats provided with different diets. Diets ranged from a nutritionally complete liquid diet to starvation (water only). In the intact animals, muscles with a more tonic character (soleus) are less sensitive to starvation than are muscles with a more phasic character (extensor digitorum longus), whereas the opposite is true of denervation. In the intact animals, starvation greatly increased the amount of atrophy following denervation. In the adrenalectomized animals, starvation had no effect on the amounts of atrophy following denervation. Furthermore, adrenalectomy virtually eliminated the fiber-type differences in the amount of atrophy following denervation. In addition, a comparison between denervated muscles from intact animals and adrenalectomized animals subjected to starvation demonstrates that all denervated muscles from the adrenalectomized animals atrophy less. Finally, it was observed that although an adrenalectomized animal can tolerate 6 days of starvation, an adrenalectomized-castrated animal cannot tolerate even short periods of starvation. The difference appears to be due to low amounts of corticosterone of testicular origin.

Empirical Beam Hardening and Ring Artifact Correction for X‐Ray Grating Interferometry (EBHC‐GI)

2020 ◽  
Author(s):  
Brandon J. Nelson ◽  
Shuai Leng ◽  
Elisabeth R. Shanblatt ◽  
Cynthia H. McCollough ◽  
Thomas Koenig
Keyword(s):  
Beam Hardening ◽  
Artifact Correction ◽  
X Ray ◽  
Ring Artifact

Dosimetric impacts of beam-hardening filter removal for the CyberKnife system

2021 ◽  
Vol 86 ◽  
pp. 98-105
Author(s):  
Takeshi Kamomae ◽  
Takuma Matsunaga ◽  
Junji Suzuki ◽  
Kuniyasu Okudaira ◽  
Fumitaka Kawabata ◽  
...  
Keyword(s):  
Beam Hardening

scholarly journals Metal artifacts in intraoperative O-arm CBCT scans

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Juha I. Peltonen ◽  
Touko Kaasalainen ◽  
Mika Kortesniemi
Keyword(s):  
Image Quality ◽  
Imaging Modality ◽  
Nonlinear Effects ◽  
Exposure Level ◽  
Metal Artifacts ◽  
Imaging Protocol ◽  
Metal Implants ◽  
Comprehensive Determination

Abstract Background Cone-beam computed tomography (CBCT) has become an increasingly important medical imaging modality in orthopedic operating rooms. Metal implants and related image artifacts create challenges for image quality optimization in CBCT. The purpose of this study was to develop a robust and quantitative method for the comprehensive determination of metal artifacts in novel CBCT applications. Methods The image quality of an O-arm CBCT device was assessed with an anthropomorphic pelvis phantom in the presence of metal implants. Three different kilovoltage and two different exposure settings were used to scan the phantom both with and without the presence of metal rods. Results The amount of metal artifact was related to the applied CBCT imaging protocol parameters. The size of the artifact was moderate with all imaging settings. The highest applied kilovoltage and exposure level distinctly increased artifact severity. Conclusions The developed method offers a practical and robust way to quantify metal artifacts in CBCT. Changes in imaging parameters may have nonlinear effects on image quality which are not anticipated based on physics.

scholarly journals Robust and Accurate Mandible Segmentation on Dental CBCT Scans Affected by Metal Artifacts Using a Prior Shape Model

2021 ◽  
Vol 11 (5) ◽  
pp. 364
Author(s):  
Bingjiang Qiu ◽  
Hylke van der van der Wel ◽  
Joep Kraeima ◽  
Haye Hendrik Glas ◽  
Jiapan Guo ◽  
...  
Keyword(s):  
State Of The Art ◽  
Maxillofacial Surgery ◽  
Cone Beam ◽  
Oral And Maxillofacial Surgery ◽  
Metal Artifacts ◽  
Shape Model ◽  
High Attenuation ◽  
Mandible Shape ◽  
Prior Shape ◽  
Segmentation Models

Accurate mandible segmentation is significant in the field of maxillofacial surgery to guide clinical diagnosis and treatment and develop appropriate surgical plans. In particular, cone-beam computed tomography (CBCT) images with metal parts, such as those used in oral and maxillofacial surgery (OMFS), often have susceptibilities when metal artifacts are present such as weak and blurred boundaries caused by a high-attenuation material and a low radiation dose in image acquisition. To overcome this problem, this paper proposes a novel deep learning-based approach (SASeg) for automated mandible segmentation that perceives overall mandible anatomical knowledge. SASeg utilizes a prior shape feature extractor (PSFE) module based on a mean mandible shape, and recurrent connections maintain the continuity structure of the mandible. The effectiveness of the proposed network is substantiated on a dental CBCT dataset from orthodontic treatment containing 59 patients. The experiments show that the proposed SASeg can be easily used to improve the prediction accuracy in a dental CBCT dataset corrupted by metal artifacts. In addition, the experimental results on the PDDCA dataset demonstrate that, compared with the state-of-the-art mandible segmentation models, our proposed SASeg can achieve better segmentation performance.

scholarly journals Dynamic Quantitative Iodine Myocardial Perfusion Imaging with Dual-Layer CT using a Porcine Model

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Kai Scherer ◽  
Johannes Hammel ◽  
Thorsten Sellerer ◽  
Korbinian Mechlem ◽  
Bernhard Renger ◽  
...  
Keyword(s):  
Contrast Agent ◽  
Perfusion Imaging ◽  
Porcine Model ◽  
Ct Perfusion ◽  
Dual Energy Ct ◽  
Beam Hardening ◽  
Low Contrast ◽  
Time To Peak ◽  
Coronary Ct

Abstract Ischemic heart disease is the globally leading cause of death. When using coronary CT angiography, the functional hemodynamics within the myocardium remain uncertain. In this study myocardial CT perfusion imaging using iodine contrast agent demonstrated to strongly improve the assessment of myocardial disorders. However, a retrieval of such dynamics using Hounsfield units from conventional CT poses concerns with respect to beam-hardening effects and low contrast-to-noise ratio (CNR). Dual-energy CT offers novel approaches to overcome aforementioned limitations. Quantitative peak enhancement, perfusion, time to peak and iodine volume measurements inside the myocardium were determined resulting in 0.92 mg/ml, 0.085 mg/ml/s 17.12 s and 29.89 mg/ml*s, respectively. We report on the first extensive quantitative and iodine-based analysis of myocardial dynamics in a healthy porcine model using a dual-layer spectral CT. We further elucidate on the potential of reducing the radiation dose from 135 to 18 mGy and the contrast agent volume from 60 to 30 mL by presenting a two-shot acquisition approach and measuring iodine concentrations in the myocardium in-vivo down to 1 mg/ml, respectively. We believe that dynamic quantitative iodine perfusion imaging may be a highly sensitive tool for the precise functional assessment and monitoring of early myocardial ischemia.

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