scholarly journals An Investigation of Calibration Phantoms for CT Scanners with Tube Voltage Modulation

2013 ◽  
Vol 2013 ◽  
pp. 1-8
Author(s):  
Jing Zou ◽  
Xiaodong Hu ◽  
Hanyu Lv ◽  
Xiaotang Hu
Keyword(s):  
Correction Method ◽  
Field Of View ◽  
Projection Data ◽  
Tube Voltage ◽  
Calibration Phantom ◽  
Proper Size ◽  
Geometry Parameter ◽  
Dual Material ◽  
Single Material ◽  
Material Calibration

The effects of calibration phantoms on the correction results of the empirical artifacts correction method (ECCU) for the case of tube modulation were investigated. To improve the validity of the ECCU method, the effect of the geometry parameter of a typical single-material calibration phantom (water calibration phantom) on the ECCU algorithm was investigated. Dual-material calibration phantoms (such as water-bone calibration phantom), geometry arrangement, and the area-ratio of dual-material calibration phantoms were also studied. Preliminary results implied that, to assure the effectiveness of the ECCU algorithm, the polychromatic projections of calibration phantoms must cover the polychromatic projection data of the scanning object. However, the projection range of a water calibration phantom is limited by the scan field of view (SFOV), thus leading to methodological limitations. A dual-material phantom of a proper size and material can overcome the limitations of a single-material phantom and achieve good correction effects.

STUDY OF DUAL-MATERIAL GATE (DMG) FinFET USING THREE-DIMENSIONAL NUMERICAL SIMULATION

2006 ◽  
Vol 05 (04n05) ◽  
pp. 541-545 ◽  
Author(s):  
DNAYNESH S. HAVALDAR ◽  
AMITAVA DASGUPTA ◽  
NANDITA DASGUPTA
Keyword(s):  
Carrier Transport ◽  
Three Dimensional ◽  
The Novel ◽  
Short Channel Effects ◽  
Short Channel ◽  
Transport Efficiency ◽  
Channel Effects ◽  
Dual Material ◽  
Single Material ◽  
Numerical Simulator

In this work, the novel characteristics of a FinFET with dual-material gate (DMG) are explored theoretically using a 3D numerical simulator and compared with those of a single material gate (SMG) FinFET in terms of threshold voltage roll off, drain induced barrier lowering (DIBL) and the ratio of transconductance (gm) to drain conductance (gd). Our studies show that the DMG structure achieves simultaneous suppression of short channel effects (SCEs), enhancement in carrier transport efficiency and transconductance. Also, these features can be controlled by engineering the work function and length of gate material.

scholarly journals Quantitative dual-energy CT material decomposition of holmium microspheres: local concentration determination evaluated in phantoms and a rabbit tumor model

2020 ◽  
Vol 31 (1) ◽  
pp. 139-148
Author(s):  
Ralf Gutjahr ◽  
Robbert C. Bakker ◽  
Feiko Tiessens ◽  
Sebastiaan A. van Nimwegen ◽  
Bernhard Schmidt ◽  
...  
Keyword(s):  
Tumor Model ◽  
Dual Energy ◽  
Dual Energy Ct ◽  
Local Concentration ◽  
Third Generation ◽  
Ct Scanner ◽  
Material Decomposition ◽  
Tube Voltage ◽  
Calibration Phantom ◽  
Ct System

Abstract Objectives The purpose of this study was to assess the feasibility of dual-energy CT-based material decomposition using dual-X-ray spectra information to determine local concentrations of holmium microspheres in phantoms and in an animal model. Materials and methods A spectral calibration phantom with a solution containing 10 mg/mL holmium and various tube settings was scanned using a third-generation dual-energy CT scanner to depict an energy-dependent and material-dependent enhancement vectors. A serial dilution of holmium (microspheres) was quantified by spectral material decomposition and compared with known holmium concentrations. Subsequently, the feasibility of the spectral material decomposition was demonstrated in situ in three euthanized rabbits with injected (radioactive) holmium microspheres. Results The measured CT values of the holmium solutions scale linearly to all measured concentrations and tube settings (R2 = 1.00). Material decomposition based on CT acquisitions using the tube voltage combinations of 80/150 Sn kV or 100/150 Sn kV allow the most accurate quantifications for concentrations down to 0.125 mg/mL holmium. Conclusion Dual-energy CT facilitates image-based material decomposition to detect and quantify holmium microspheres in phantoms and rabbits. Key Points • Quantification of holmium concentrations based on dual-energy CT is obtained with good accuracy. • The optimal tube-voltage pairs for quantifying holmium were 80/150 Sn kV and 100/150 Sn kV using a third-generation dual-source CT system. • Quantification of accumulated holmium facilitates the assessment of local dosimetry for radiation therapies.

scholarly journals Kinect-Based Correction of Overexposure Artifacts in Knee Imaging with C-Arm CT Systems

2016 ◽  
Vol 2016 ◽  
pp. 1-15 ◽  
Author(s):  
Johannes Rausch ◽  
Andreas Maier ◽  
Rebecca Fahrig ◽  
Jang-Hwan Choi ◽  
Waldo Hinshaw ◽  
...  
Keyword(s):  
Weight Bearing ◽  
Calibration Procedure ◽  
Correction Method ◽  
Projection Data ◽  
Near Surface ◽  
Depth Cameras ◽  
Kinect Camera ◽  
Novel Approach ◽  
Knee Imaging ◽  
Cross Calibration

Objective.To demonstrate a novel approach of compensating overexposure artifacts in CT scans of the knees without attaching any supporting appliances to the patient. C-Arm CT systems offer the opportunity to perform weight-bearing knee scans on standing patients to diagnose diseases like osteoarthritis. However, one serious issue is overexposure of the detector in regions close to the patella, which can not be tackled with common techniques.Methods.A Kinect camera is used to algorithmically remove overexposure artifacts close to the knee surface. Overexposed near-surface knee regions are corrected by extrapolating the absorption values from more reliable projection data. To achieve this, we develop a cross-calibration procedure to transform surface points from the Kinect to CT voxel coordinates.Results.Artifacts at both knee phantoms are reduced significantly in the reconstructed data and a major part of the truncated regions is restored.Conclusion.The results emphasize the feasibility of the proposed approach. The accuracy of the cross-calibration procedure can be increased to further improve correction results.Significance.The correction method can be extended to a multi-Kinect setup for use in real-world scenarios. Using depth cameras does not require prior scans and offers the possibility of a temporally synchronized correction of overexposure artifacts. To achieve this, we develop a cross-calibration procedure to transform surface points from the Kinect to CT voxel coordinates.

Three-dimensional printing of dual thermoplastic materials with different layer combinations: Tensile, flexural, and fractured surface investigations

2020 ◽  
pp. 089270572092512 ◽  
Author(s):  
Sudhir Kumar ◽  
Rupinder Singh ◽  
TP Singh ◽  
Ajay Batish ◽  
Akshay Kumar
Keyword(s):  
Fused Deposition Modeling ◽  
Mechanical Performance ◽  
Three Dimensional ◽  
Acrylonitrile Butadiene Styrene ◽  
Thermoplastic Material ◽  
Fused Deposition ◽  
Multiple Materials ◽  
Dual Material ◽  
Single Material ◽  
Fractured Surface

The three-dimensional (3-D) printing with deposition of dual/multiple materials on alternative layers has been explored by some researchers for various engineering applications. But, hitherto, little has been reported on failure mechanism of dual/multiple materials 3-D printed parts in tensile and flexural testing. In this work, investigations were made to explore the tensile, flexural, morphological, and thermal properties of dual thermoplastic material (acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA))-based 3-D printing of functional prototypes with low-cost fused deposition modeling process. The results of the study suggest that for mechanical properties of 3-D printed parts, the number of conversions, the number of negative conversions for selecting particular layer of thermoplastic material, and the number of layers (while selecting the alternative layer’s material) have significant effect. The maximum peak strength of 55.98 MPa (while tensile testing) was observed for combination of four consecutive layers of PLA and two layers of ABS, which is 15.81% higher than the ABS (48.34 MPa) and at par with the PLA-based 3-D printed functional prototype. Also, it has been ascertained that the deposition of ABS on PLA has better compatibility than PLA deposition on ABS platform. In case of flexural strength, single material-based 3-D printed parts have better properties. From fractured surface analysis, it has been observed that dual material-based 3-D printed prototypes have relatively large number of voids/porosity holes in comparison to single material-based 3-D printed prototypes, thus ultimately resulting in poor mechanical performance.

scholarly journals Exploring field-of-view non-uniformities produced by a hand-held spectroradiometer

2011 ◽  
Author(s):  
Tamir Caras ◽  
Arnon Karnieli ◽  
John Hedley
Keyword(s):  
Correction Method ◽  
Linear Displacement ◽  
Accurate Prediction ◽  
Field Of View ◽  
Spectral Measurements ◽  
Spatial Sensitivity ◽  
Other Hand ◽  
Laser Guide ◽  
The Relationship ◽  
The Way

The shape of a spectroradiometer’s field of view (FOV) affects the way spectral measurements are acquired. Knowing this property is a prerequisite for the correct use of the spectrometer. If the substrate is heterogeneous, the ability to accurately know what is being measured depends on knowing the FOV location, shape, spectral and spatial sensitivity. The GER1500 is a hand-held spectrometer with a fixed lens light entry slit and has a laser guide that allows control over the target by positioning the entire unit. In the current study, the FOV of the GER1500 was mapped and analysed. The spectral and spatial non-uniformities of the FOV were examined and were found to be spectrally independent. The relationship between the FOV and the built-in laser guide was tested and found to have a linear displacement dependent on the distance to the target. This allows an accurate prediction of the actual FOV position.  A correction method to improve the agreement between the expected and measured reflectance over heterogeneous targets was developed and validated. The methods described are applicable and may be of use with other hand-held spectroradiometers.

scholarly journals Detection of wakes in the inflow of turbines using nacelle lidars

2019 ◽  
Author(s):  
Dominique P. Held ◽  
Jakob Mann
Keyword(s):  
Wind Direction ◽  
Empirical Relationship ◽  
Correction Method ◽  
Detection Algorithm ◽  
Field Of View ◽  
Doppler Spectrum ◽  
Small Scale ◽  
Ambient Flow ◽  
The Difference ◽  
Scale Turbulence

Abstract. Nacelle-mounted lidar systems offer the possibility of remotely sensing the inflow of wind turbines. Due to the limitation of line-of-sight measurements and the limited number of focus positions, assumptions are necessary to derive useful inflow characteristics. Typically, horizontally homogeneous inflow is assumed which is well satisfied in flat, homogeneous terrain and over sufficiently large time averages. However, it is violated if a wake impinges the field of view of one of the beams. In such situations, the turbine yaw misalignment measurements show large biases which require the detection and correction of these observations. Here, a detection algorithm is proposed based on the spectral broadening of the Doppler spectrum due to turbulence within the probe volume. The small-scale turbulence generated within wake flows will typically lead to a significantly larger broadening than in the ambient flow. Thus, by comparing the spectral widths at several locations, situations, where a wake is impinging the field of view of one or more beams can be identified. The correction method is based on an empirical relationship between the difference in turbulence levels at distinct beams and the difference in wind direction derived from the lidar and the real wind direction. The performance of the algorithm is evaluated in a field experiment identifying all wake situations, and thus, correcting the lidar derived wind direction.

scholarly journals A metal artifact reduction method for small field of view CT imaging

2019 ◽  
Author(s):  
Seungwon Choi ◽  
Seunghyuk Moon ◽  
Jongduk Baek
Keyword(s):  
Mean Squared Error ◽  
Main Idea ◽  
Previous Method ◽  
Field Of View ◽  
Projection Data ◽  
Artifact Reduction ◽  
Metal Artifact ◽  
Metal Artifact Reduction ◽  
Metal Artifacts ◽  
Data Truncation

AbstractTo reduce metal artifacts, several sinogram inpainting-based metal artifact reduction (MAR) methods have been proposed where projection data within the metal trace region of the sinogram are treated as missing and subsequently estimated. However, these methods generally assume data truncation does not occur and all metal objects reside inside the field-of-view (FOV). For small FOV imaging, these assumptions are violated, and thus existing inpainting-based MAR methods would not be effective. In this paper, we propose a new MAR method to reduce metal artifacts effectively in the presence of data truncation. The main idea behind the proposed method is the synthesis of a sinogram, which is treated as the originally measured sinogram. First, an initial reconstruction step is performed to remove truncation artifacts. The next step consists of a forward projection of the small FOV image, replacing the original sinogram with the synthesized sinogram. The final step is the application of sinogram inpainting based MAR methods using the synthesized sinogram. Verification of the proposed method was performed for three situations: extended cardiac-torso (XCAT) simulation, clinical data, and experimental data. The proposed method was applied with linear MAR (LMAR) and normalized MAR (NMAR), and the performance of the proposed method was compared with that of the previous method. For quantitative evaluation, normalized mean squared error (NMSE) and structure similarity (SSIM) were used. The results show the effectiveness of the proposed method to reduce residual metal artifacts, which are present in the results obtained with the previous method. The evaluation results using NMSE and SSIM also indicate that the proposed method is more effective than the previous method.

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