scholarly journals A New Statistical Reconstruction Method for the Computed Tomography Using an X-Ray Tube with Flying Focal Spot

2021 ◽  
Vol 11 (4) ◽  
pp. 271-286
Author(s):  
Robert Cierniak ◽  
Piotr Pluta ◽  
Marek Waligóra ◽  
Zdzisław Szymański ◽  
Konrad Grzanek ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Focal Spot ◽  
Reconstruction Method ◽  
Reconstruction Procedure ◽  
X Ray ◽  
Statistical Reconstruction ◽  
Reconstruction Methods ◽  
Ct Scanners ◽  
The Impact

Abstract This paper presents a new image reconstruction method for spiral cone- beam tomography scanners in which an X-ray tube with a flying focal spot is used. The method is based on principles related to the statistical model-based iterative reconstruction (MBIR) methodology. The proposed approach is a continuous-to-continuous data model approach, and the forward model is formulated as a shift-invariant system. This allows for avoiding a nutating reconstruction-based approach, e.g. the advanced single slice rebinning methodology (ASSR) that is usually applied in computed tomography (CT) scanners with X-ray tubes with a flying focal spot. In turn, the proposed approach allows for significantly accelerating the reconstruction processing and, generally, for greatly simplifying the entire reconstruction procedure. Additionally, it improves the quality of the reconstructed images in comparison to the traditional algorithms, as confirmed by extensive simulations. It is worth noting that the main purpose of introducing statistical reconstruction methods to medical CT scanners is the reduction of the impact of measurement noise on the quality of tomography images and, consequently, the dose reduction of X-ray radiation absorbed by a patient. A series of computer simulations followed by doctor’s assessments have been performed, which indicate how great a reduction of the absorbed dose can be achieved using the reconstruction approach presented here.

scholarly journals Reconstruction of High-Resolution Computed Tomography Image in Sinogram Space

2021 ◽  
Vol 15 ◽  
pp. 84-88
Author(s):  
Osama A. Omer
Keyword(s):  
Computed Tomography ◽  
High Resolution ◽  
Image Quality ◽  
Computational Cost ◽  
Super Resolution ◽  
Reconstruction Method ◽  
High Resolution Computed Tomography ◽  
Resolution Image ◽  
Reconstruction Methods

An important part of any computed tomography (CT) system is the reconstruction method, which transforms the measured data into images. Reconstruction methods for CT can be either analytical or iterative. The analytical methods can be exact, by exact projector inversion, or non-exact based on Back projection (BP). The BP methods are attractive because of thier simplicity and low computational cost. But they produce suboptimal images with respect to artifacts, resolution, and noise. This paper deals with improve of the image quality of BP by using super-resolution technique. Super-resolution can be beneficial in improving the image quality of many medical imaging systems without the need for significant hardware alternation. In this paper, we propose to reconstruct a high-resolution image from the measured signals in Sinogram space instead of reconstructing low-resolution images and then post-process these images to get higher resolution image.

Numerical Analysis of the Feldkamp–Davis–Kress Effect on Industrial X-Ray Computed Tomography for Dimensional Metrology

2015 ◽  
Vol 15 (2) ◽  
Author(s):  
Lin Xue ◽  
Hiromasa Suzuki ◽  
Yutaka Ohtake ◽  
Hiroyuki Fujimoto ◽  
Makoto Abe ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Ct Images ◽  
Cone Beam ◽  
Reconstruction Method ◽  
Dimensional Metrology ◽  
X Ray ◽  
Computation Efficiency ◽  
X Ray Computed ◽  
Projection Images ◽  
Ct Scanners

X-ray computed tomography (CT) can nondestructively inspect an object and can clearly, accurately, and intuitively display its internal structure, composition, texture, and damage. In industry this technology was initially used for material analysis and nondestructive testing and evaluation. Recently, as an alternative to optical and tactile measurement devices, CT has entered industrial use for dimensional metrology. Unfortunately, industrial-level accuracy is very difficult to attain with CT for various reasons. In this paper we analyze one of the most serious effects, the Feldkamp–Davis–Kress (FDK) effect, which can be observed in most of the common X-ray CT scanners with a cone beam. The FDK is the reconstruction algorithm widely accepted as a standard reconstruction method for cone-beam type of CT because of its computation efficiency. However, this algorithm merely provides an approximate result. An accurate measurement result can be obtained only in the case of small cone angle. We aim at analyzing the FDK effect independently from other kinds of artifacts. In a practical CT scanning situation, various kinds of artifacts appear in the reconstruction results; thus, we apply a simulation to obtain projection images without noise (scattering, beam hardening, etc.). Then, the FDK algorithm is applied to these projection images to reconstruct CT images so that only the FDK effect can be observed in the reconstructed CT images. Based on this approach, we conducted quantitative analysis on the FDK effect using numerical phantoms of the sphere and stepped cylinders that may be adopted as ISO reference standards for dimensional metrology using X-ray CT scanners. This paper describes the evaluation workflow and discusses the cause of the FDK effect on the measurement of the sphere and the stepped cylinders. Particular attention is given to the evaluation of the error distribution feature on different spatial positions. After discussing the error feature, a method for improving measurement accuracy is proposed.

scholarly journals Mobility and Bioavailability of Metal(loid)s in a Fluvial System Affected by the Mining and Industrial Processing of Pb

Geosciences ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 167
Author(s):  
Unai Cortada ◽  
María Carmen Hidalgo ◽  
Julián Martínez ◽  
María José de la Torre
Keyword(s):  
Total Concentration ◽  
Rare Metal ◽  
Mining District ◽  
X Ray ◽  
Industrial Processing ◽  
Solids Concentration ◽  
Mobile Fraction ◽  
Type Water ◽  
The Impact

The abandoned mining district of Linares (South Spain) is marked with waste from the mining and the processing of metal ores that pose an environmental hazard to watercourses. A combined analysis of waste, sediments and water was carried out to analyse the impact of a smelter on Baños Creek. The composition of the facility waste was determined using X-ray diffractometry and scanning electron microscopy. The total contents of the metal(loid)s in the waters and sediments of the watercourse were analysed, and sequential metal(loid) extraction of solid samples was carried out. The facility wastes consisted mainly of secondary minerals, such as natropharmacosiderite and spertiniite, as well as rare metal salts, such as mopungite and NaPb2(CO3)2(OH). The leachates generated by these wastes were highly alkaline, with a pH of 10 and a total dissolved solids concentration of approximately 9 g L−1. This Na-bicarbonate-type water had an As concentration above 200 mg L−1 and elevated levels of Pb, Sb and Zn (5029 µg L−1, 841 µg L−1 and 525 µg L−1, respectively). This highly contaminated lixiviate had a significant effect on the chemical quality of the waters and the bioavailability of metal(loid)s in the creek sediments, especially in the headwaters. In this zone, the As, Pb, Sb and Zn concentrations in the most mobile fraction of the sediments reached 1035 mg kg−1, 261 mg kg−1, 45 mg kg−1 and 30 mg kg−1, respectively. By comparison, smelter slag and mining waste have a much lower impact on the waters and the mobile fraction of the sediments, while significantly increasing the total concentration of these potentially toxic elements in creek sediments.

scholarly journals Automated evaluation of the surface point quality in dimensional X-ray computed tomography

2020 ◽  
Vol 87 (2) ◽  
pp. 111-121 ◽  
Author(s):  
Andreas Michael Müller ◽  
Lorenz Butzhammer ◽  
Florian Wohlgemuth ◽  
Tino Hausotte
Keyword(s):  
Computed Tomography ◽  
Surface Point ◽  
Random Measurement Error ◽  
X Ray ◽  
Random Measurement ◽  
Automated Evaluation ◽  
Dimensional Measurements ◽  
X Ray Computed ◽  
Model Measurement

AbstractX-ray computed tomography (CT) enables dimensional measurements of numerous measurands with a single scan, including the measurement of inner structures. However, measurement artefacts complicate the applicability of the technology in some cases. This paper presents a methodology to assess the surface point quality of computed tomography measurements without the requirement of a CAD model. Measurement artefacts lowering the surface point quality can therefore automatically be detected. The correlation of quality values with the random measurement error is demonstrated. The presented method can in principle be used to weight single fit points to reduce the measurement uncertainty of CT measurements.

scholarly journals Novel Reconstruction Using Roux-en-Y Plus Antral Obstruction Following Proximal Gastrectomy: Feasibility and Quality of Life Benefits

2019 ◽  
Author(s):  
Dejun Yang ◽  
Changming Wang ◽  
Hongbing Fu ◽  
Ziran Wei ◽  
Xin Zhang ◽  
...  
Keyword(s):  
Quality Of Life ◽  
Reflux Esophagitis ◽  
Proximal Gastrectomy ◽  
Partial Gastrectomy ◽  
Incidence Rates ◽  
Reconstruction Method ◽  
Reflux Symptoms ◽  
Reconstruction Methods ◽  
Postoperative Reflux

Abstract Background and Aims Routine gastroesophagostomy has been shown to have adverse effects on the recovery of digestive functions and quality of life because patients typically experience reflux symptoms after proximal gastrectomy. This study was performed to assess the feasibility and quality of life benefits of a novel reconstruction method termed Roux-en-Y anastomosis plus antral obstruction (RYAO) following proximal partial gastrectomy. Methods A total of 73 patients who underwent proximal gastrectomy from June 2015 to June 2017 were divided into two groups according to digestive reconstruction methods [RYAO (37 patients) and conventional esophagogastric anastomosis with pyloroplasty (EGPP, 36 patients)]. Clinical data were compared between the two groups retrospectively. Results The mean operative time for digestive reconstruction was slightly longer in the RYAO group than in the EGPP group. However, the incidence of postoperative short-term complications did not differ between the RYAO and the EGPP groups. At the 6-month follow-up, the incidence rates of both reflux esophagitis and gastritis were lower in the RYAO group than in the EGPP group (P = 0.002). Additionally, body weight recovery was better in the RYAO group (P = 0.028). The scale tests indicated that compared with the patients in the EGPP group, the patients in the RYAO group had significantly reduced reflux, nausea and vomiting and reported improvements in their overall health status and quality of life (all P < 0.05). Conclusion RYAO reconstruction may be a feasible procedure to reduce postoperative reflux symptoms and the incidence of reflux esophagitis and gastritis, thus improving patient quality of life after proximal gastrectomy.

THE IMPACT OF HEAD POSITIONING ON THE IMAGE QUALITY OF MULTI-DETECTOR COMPUTED TOMOGRAPHY

2021 ◽  
pp. 2150050
Author(s):  
Yang-Ting Hsu ◽  
Jo-Chi Jao
Keyword(s):  
Computed Tomography ◽  
Image Quality ◽  
Control Group ◽  
Ct Scanner ◽  
Head Ct ◽  
Radiologic Technologists ◽  
Head Positioning ◽  
The Impact ◽  
Multi Detector Computed Tomography

Radiologic technologists face various types of patients during multi-detector computed tomography (CT) examinations. In emergency departments, it is common to have patients who cannot follow instructions for the examinations. The asymmetric axial view of the head CT might affect the correctness of the clinician’s diagnosis. This study aimed to assess the impact of head positioning on the image quality of head CT using two phantoms. All scans were performed on a 16-slice CT scanner. In the control group, the tilted angle of the phantoms was 0[Formula: see text], and no multiplanar reconstruction (MPR) was performed. In the experimental groups, the tilted angles of the phantoms were 5[Formula: see text], 10[Formula: see text] and 15[Formula: see text], respectively, and MPR was performed afterwards. The results showed that if the head was tilted during the head CT examinations, image asymmetry and artifacts appeared without MPR. After MPR, one phantom showed that there were significant differences and the other phantom showed no significant differences quantitatively in image symmetry and artifacts between experimental groups and the control group, while both phantoms showed no significant differences qualitatively in image symmetry and artifacts between experimental groups and the control group. Although MPR can correct the image asymmetry and artifacts caused by tilted head positioning to some extent, it consumes time. Therefore, technologists should position the head as exactly as possible when performing head CT examinations.

Abstract 5799: Fine-Cell Detector Computed Tomography with 0.3mm-Collimation Improves Quantitative Assessment of Coronary Artery Stenosis: Experimental Study with Coronary Phantom

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Minoru yamada ◽  
Masahiro Jinzaki ◽  
Kozo Sato ◽  
Yutaka Tanami ◽  
Akihisa Ueno ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Coronary Artery ◽  
Focal Spot ◽  
Coronary Artery Stenosis ◽  
Hounsfield Unit ◽  
Acrylonitrile Butadiene Styrene ◽  
Artery Stenosis ◽  
Data Sets ◽  
Water Tank ◽  
X Ray

The purpose of this study was to evaluate whether the prototype fine-cell detector computed tomography (FDCT) could improve smaller coronary artery stenosis measurement compared with 64-slice multidetector-row CT (MDCT). Method and Materials: We developed coronary phantoms of 2mm in diameter with 0%, 25%, 50%, 75% stenosis. Each stenotic part was made by Acrylonitrile-Butadiene-Styrene (ABS: 50 Hounsfield Unit (HU)) and lumen was filled with diluted iodine (380 HU). These coronary phantoms put into the water tank were scanned by both prototype FDCT and 64-slice MDCT. Configuration of FDCT was 32-row*0.3125mm detector collimation with 0.35mm smaller X-ray tube focal spot width, and that of 64-slice MDCT was 16-row*0.625mm detector collimation and 0.7mm X-ray focal spot. All axial images were reconstructed using Standard kernel with 96mm display field-of-view. Minimum lumen diameter and degree of stenosis in these data sets were automatically measured using the Vessel Analysis software (GE Healthcare). Results: Measured coronary lumen at 0%, 25%, 50%, 75% stenosis of 2mm-diameter phantom (corresponding to 2.0mm, 1.5mm, 1.0mm, 0.5mm) were 2.2mm, 1.8mm, 1.4mm, 0.7mm in FDCT, whereas those were 2.5mm, 2.0mm, 1.5mm, 1.4mm in 64-slice MDCT, respectively. Each degree of stenosis was calculated 21%, 38%, 69% in FDCT, while 20%, 38%, 44% in 64-slice MDCT. Measured value of 75% stenosis in FDCT was significantly improved compared with 64-slice MDCT. Conclusion: FDCT improves the accuracy of smaller coronary artery stenosis measurement compared with 64-slice MDCT. Superior spatial resolution of FDCT could be promising for more accurate assessment of the coronary artery stenosis.

scholarly journals Radiomics of high-resolution computed tomography for the differentiation between cholesteatoma and middle ear inflammation: effects of post-reconstruction methods in a dual-center study

2020 ◽  
Author(s):  
Christophe T. Arendt ◽  
Doris Leithner ◽  
Marius E. Mayerhoefer ◽  
Peter Gibbs ◽  
Christian Czerny ◽  
...  
Keyword(s):  
Computed Tomography ◽  
High Resolution ◽  
Middle Ear ◽  
Characteristic Curve ◽  
High Resolution Computed Tomography ◽  
Probability Of Error ◽  
Haar Wavelet Transform ◽  
Reconstruction Methods ◽  
The Impact ◽  
Center Study

Abstract Objectives To evaluate the performance of radiomic features extracted from high-resolution computed tomography (HRCT) for the differentiation between cholesteatoma and middle ear inflammation (MEI), and to investigate the impact of post-reconstruction harmonization and data resampling. Methods One hundred patients were included in this retrospective dual-center study: 48 with histology-proven cholesteatoma (center A: 23; center B: 25) and 52 with MEI (A: 27; B: 25). Radiomic features (co-occurrence and run-length matrix, absolute gradient, autoregressive model, Haar wavelet transform) were extracted from manually defined 2D-ROIs. The ten best features for lesion differentiation were selected using probability of error and average correlation coefficients. A multi-layer perceptron feed-forward artificial neural network (MLP-ANN) was used for radiomics-based classification, with histopathology serving as the reference standard (70% of cases for training, 30% for validation). The analysis was performed five times each on (a) unmodified data and on data that were (b) resampled to the same matrix size, and (c) corrected for acquisition protocol differences using ComBat harmonization. Results Using unmodified data, the MLP-ANN classification yielded an overall median area under the receiver operating characteristic curve (AUC) of 0.78 (0.72–0.84). Using original data from center A and resampled data from center B, an overall median AUC of 0.88 (0.82–0.99) was yielded, while using ComBat harmonized data, an overall median AUC of 0.89 (0.79–0.92) was revealed. Conclusion Radiomic features extracted from HRCT differentiate between cholesteatoma and MEI. When using multi-centric data obtained with differences in CT acquisition parameters, data resampling and ComBat post-reconstruction harmonization clearly improve radiomics-based lesion classification. Key Points • Unenhanced high-resolution CT coupled with radiomics analysis may be useful for the differentiation between cholesteatoma and middle ear inflammation. • Pooling of data extracted from inhomogeneous CT datasets does not appear meaningful without further post-processing. • When using multi-centric CT data obtained with differences in acquisition parameters, post-reconstruction harmonization and data resampling clearly improve radiomics-based soft-tissue differentiation.

Optimising the Growth of Few-Layer Graphene on Silicon Carbide by Nickel Silicidation

2013 ◽  
Vol 740-742 ◽  
pp. 121-124 ◽  
Author(s):  
Enrique Escobedo-Cousin ◽  
Konstantin Vassilevski ◽  
Toby Hopf ◽  
Nick G. Wright ◽  
Anthony O’Neill ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Solid Phase ◽  
Sample Surface ◽  
Device Fabrication ◽  
Solid Phase Epitaxy ◽  
X Ray ◽  
Graphene Films ◽  
Few Layer Graphene ◽  
The Impact

Few-layers graphene films (FLG) were grown by local solid phase epitaxy on a semi-insulating 6H-SiC substrate by annealing Ni films deposited on the Si and C-terminated faces of the SiC. The impact of the annealing process on the final quality of the FLG films is studied using Raman spectroscopy. X-ray photoelectron spectroscopy was used to verify the presence of graphene on the sample surface. We also demonstrate that further device fabrication steps such as dielectric deposition can be carried out without compromising the FLG films integrity.

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