scholarly journals Narrow-Energy-Width CT Based on Multivoltage X-Ray Image Decomposition

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Jiaotong Wei ◽  
Yan Han ◽  
Ping Chen
Keyword(s):  
Computed Tomography ◽  
Low Frequency ◽  
Image Decomposition ◽  
Frequency Characteristics ◽  
Reconstructed Image ◽  
X Ray ◽  
Energy Width ◽  
Quantitative Measurements ◽  
X Ray Scattering ◽  
Ct System

A polychromatic X-ray beam causes the grey of the reconstructed image to depend on its position within a solid and the material being imaged. This factor makes quantitative measurements via computed tomography (CT) imaging very difficult. To obtain a narrow-energy-width reconstructed image, we propose a model to decompose multivoltage X-ray images into many narrow-energy-width X-ray images by utilizing the low frequency characteristics of X-ray scattering. It needs no change of hardware in the typical CT system. Solving the decomposition model, narrow-energy-width projections are obtained and it is used to reconstruct the image. A cylinder composed of aluminum and silicon is used in a verification experiment. Some of the reconstructed images could be regarded as real narrow-energy-width reconstructed images, which demonstrates the effectiveness of the proposed method.

A feasibility study of time of flight cone beam computed tomography imaging

2021 ◽  
pp. 1-14
Author(s):  
Ignacio O. Romero ◽  
Changqing Li
Keyword(s):  
Computed Tomography ◽  
Cone Beam Computed Tomography ◽  
Time Of Flight ◽  
Cone Beam ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Effects ◽  
Breast Phantom ◽  
Scatter Reduction ◽  
Strong Scattering

BACKGROUND: The time of flight (TOF) cone beam computed tomography (CBCT) was recently shown to reduce the X-ray scattering effects by 95%and improve the image CNR by 110%for large volume objects. The advancements in X-ray sources like in compact Free Electron Lasers (FEL) and advancements in detector technology show potential for the TOF method to be feasible in CBCT when imaging large objects. OBJECTIVE: To investigate feasibility and efficacy of TOF CBCT in imaging smaller objects with different targets such as bones and tumors embedded inside the background. METHODS: The TOF method used in this work was verified using a 24cm phantom. Then, the GATE software was used to simulate the CBCT imaging of an 8 cm diameter cylindrical water phantom with two bone targets using a modeled 20 keV quasi-energetic FEL source and various TOF resolutions ranging from 1 to 1000 ps. An inhomogeneous breast phantom of similar size with tumor targets was also imaged using the same system setup. RESULTS: The same results were obtained in the 24cm phantom, which validated the applied CBCT simulation approach. For the case of 8cm cylindrical phantom and bone target, a TOF resolution of 10 ps improved the image contrast-to-noise ratio (CNR) by 57%and reduced the scatter-to-primary ratio (SPR) by 8.63. For the case of breast phantom and tumor target, image CNR was enhanced by 12%and SPR was reduced by 1.35 at 5 ps temporal resolution. CONCLUSIONS: This study indicates that a TOF resolution below 10 ps is required to observe notable enhancements in the image quality and scatter reduction for small objects around 8cm in diameter. The strong scattering targets such as bone can result in substantial improvements by using TOF CBCT.

Image Quality Assessment of Low-Dose CT using Hybrid Iterative Reconstruction

2021 ◽  
Author(s):  
Qiao Zhang ◽  
Jinhua Sheng ◽  
Bin Chen
Keyword(s):  
Computed Tomography ◽  
Noise Reduction ◽  
Iterative Reconstruction ◽  
Low Dose ◽  
Low Frequency ◽  
Image Noise ◽  
Observer Performance ◽  
Human Observer ◽  
X Ray ◽  
Hybrid Iterative Reconstruction

Background: X-ray computed tomography is the first imaging technology that supports accurate nondestructive interior image reconstruction of an object from sufficient projection data. Low-dose computed tomography (LDCT) has been considered to relieve the harm to patients caused by X-ray radiation. However, LDCT images can be degraded by quantum noise and streak artifacts. Methods: The objective of the authors’ study is to evaluate the optimal level of the hybrid iterative reconstruction (HIR) that generates images with the best diagnostic quality on different dose and noise levels. HIR with optimizations is proposed to reduce image noise and provide better performance at a low dose. The Catphan R 504 phantom is employed to assess various image qualities (IQ). Results: For any given scanning protocols, there is linear noise reduction and linear increase of contrast-to- noise ratio (CNR) using optimal HIR. The evidence from various module tests demonstrates that the shape of the noise power spectrum is continuously shifted to low frequency with increasing HIR levels compared with that of filtered-back-projection (FBP). This may describe the difference between the human observer performance and features of the ideal low-contrast objects. Conclusion: Optimal HIR is clearly demonstrated to be a superior method for reducing image noise and improving CNR compared to FBP. Optimal HIR also inhibits texture change or spectrum shift compared with the pure IR method. Even though there are continuous noise reduction and CNR increase with HIR at increasing levels, the human observer performance does not seem to improve simultaneously due to coarser noise (low-frequency noise). HIR level 3 to 5 is optimal for their study. It is possible for the optimal HIR to offer equivalent diagnostic IQ at a lower dose compared with FBP at a routine dose.

scholarly journals Synchrotron and Raman Study of the Rotator Phases and Polymorphism in Tricosane Paraffin

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1341
Author(s):  
Enrique Blázquez-Blázquez ◽  
Rosa Barranco-García ◽  
María L. Cerrada ◽  
Juan C. Martínez ◽  
Ernesto Pérez
Keyword(s):  
Phase Behavior ◽  
Variable Temperature ◽  
Low Frequency ◽  
Frequency Region ◽  
Time Variable ◽  
Wide Angle ◽  
Multistage Model ◽  
X Ray ◽  
X Ray Scattering ◽  
Raman Study

A detailed study of the phase behavior of n-paraffin C23H48 has been performed by means of real-time variable-temperature experiments with synchrotron radiation. Two detectors were employed for simultaneous analysis of the small-angle (SAXS) and wide-angle X-ray-scattering (WAXS) regions. This paraffin presents a very interesting phase behavior, involving two crystal polymorphs, three rotator phases and the liquid state. The Ostwald rule of stages is invoked to find similarities of the rotator phases with the eventual transient mesomorphic structure in the multistage model of polymer crystallization. That study is complemented by variable-temperature Raman experiments covering frequencies down to 150 cm−1. It was found that the low-frequency region is the most informative regarding the phase transitions, and specifically the intensity of the first overtone. From these analyses, several parameters are evaluated as function of temperature.

scholarly journals Automated Analysis of Spatially Resolved X-ray Scattering and Micro Computed Tomography of Artificial and Natural Enamel Carious Lesions

2018 ◽  
Vol 4 (6) ◽  
pp. 81 ◽  
Author(s):  
Hans Deyhle ◽  
Shane White ◽  
Lea Botta ◽  
Marianne Liebi ◽  
Manuel Guizar-Sicairos ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Automated Analysis ◽  
Micro Computed Tomography ◽  
X Ray ◽  
Spatially Resolved ◽  
X Ray Scattering ◽  
Carious Lesions ◽  
Ray Scattering

Improving the efficiency of small-angle x-ray scattering computed tomography using the OSEM algorithm

2017 ◽  
Vol 56 (30) ◽  
pp. 8326 ◽  
Author(s):  
Tao Hu ◽  
Yudan Wang ◽  
Guohao Du ◽  
Yuzhu Wang ◽  
Wenqiang Hua ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Small Angle ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

scholarly journals Improving grazing-incidence small-angle X-ray scattering–computed tomography images by total variation minimization

2020 ◽  
Vol 53 (1) ◽  
pp. 140-147
Author(s):  
Hiroki Ogawa ◽  
Shunsuke Ono ◽  
Yukihiro Nishikawa ◽  
Akihiko Fujiwara ◽  
Taizo Kabe ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Image Quality ◽  
Total Variation ◽  
Small Angle ◽  
Grazing Incidence ◽  
Ct Images ◽  
Measurement Time ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Grazing-incidence small-angle X-ray scattering (GISAXS) coupled with computed tomography (CT) has enabled the visualization of the spatial distribution of nanostructures in thin films. 2D GISAXS images are obtained by scanning along the direction perpendicular to the X-ray beam at each rotation angle. Because the intensities at the q positions contain nanostructural information, the reconstructed CT images individually represent the spatial distributions of this information (e.g. size, shape, surface, characteristic length). These images are reconstructed from the intensities acquired at angular intervals over 180°, but the total measurement time is prolonged. This increase in the radiation dosage can cause damage to the sample. One way to reduce the overall measurement time is to perform a scanning GISAXS measurement along the direction perpendicular to the X-ray beam with a limited interval angle. Using filtered back-projection (FBP), CT images are reconstructed from sinograms with limited interval angles from 3 to 48° (FBP-CT images). However, these images are blurred and have a low image quality. In this study, to optimize the CT image quality, total variation (TV) regularization is introduced to minimize sinogram image noise and artifacts. It is proposed that the TV method can be applied to downsampling of sinograms in order to improve the CT images in comparison with the FBP-CT images.

scholarly journals Artifact removal in the contour areas of SAXS-CT images by Tikhonov-L1 minimization

2021 ◽  
Vol 54 (6) ◽  
Author(s):  
Hiroki Ogawa ◽  
Shunsuke Ono ◽  
Yuki Watanabe ◽  
Yukihiro Nishikawa ◽  
Shotaro Nishitsuji ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Incident Beam ◽  
Ct Image ◽  
Characteristic Parameters ◽  
Artifact Removal ◽  
L1 Minimization ◽  
X Ray ◽  
Nanoscale Structures ◽  
X Ray Scattering ◽  
Surface Length

Small-angle X-ray scattering (SAXS) coupled with computed tomography (CT), denoted SAXS-CT, has enabled the spatial distribution of the characteristic parameters (e.g. size, shape, surface, length) of nanoscale structures inside samples to be visualized. In this work, a new scheme with Tikhonov regularization was developed to remove the effects of artifacts caused by streak scattering originating from the reflection of the incident beam in the contour regions of the sample. The noise due to streak scattering was successfully removed from the sinogram image and hence the CT image could be reconstructed free from artifacts in the contour regions.

Quantitative Anatomy of the Thoracolumbar Epidural Space

Neurosurgery ◽  
1985 ◽  
Vol 17 (6) ◽  
pp. 905-907 ◽  
Author(s):  
Arden F. Reynolds ◽  
P. Alex Roberts ◽  
Michael Pollay ◽  
Phillip H. Stratemeier
Keyword(s):  
Computed Tomography ◽  
Chronic Pain ◽  
Epidural Space ◽  
Iodized Oil ◽  
X Ray ◽  
Quantitative Measurements ◽  
Quantitative Anatomy ◽  
Made In

Abstract Quantitative measurements of the epidural space between T-7 and L-4 were made in the sagittal and coronal planes utilizing x-ray films made after the injection of iodized oil into the epidural space in the low thoracic and upper lumbar areas. These data reveal a 1-mm ventral epidural space and a 2-mm lateral epidural space, with a sawtooth shape to the dorsal epidural space measuring between 1.1 and 2.9 mm at the rostral lamina and between 3.8 and 6.5 mm at the caudal lamina. Additionally, five patients with chronic pain were studied by computed tomography of T-8 to T-12, with confirmation of the sawtooth shape of the dorsal epidural space. Computed tomography showed the measurements of the epidural space at the rostral lamina to vary between 1.3 and 1.6 mm and those at the caudal lamina/interlaminar space to range from 6.9 to 9.1 mm.

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