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.

scholarly journals Shearlet-based regularized reconstruction in region-of-interest computed tomography

2018 ◽  
Vol 13 (4) ◽  
pp. 34
Author(s):  
T.A. Bubba ◽  
D. Labate ◽  
G. Zanghirati ◽  
S. Bonettini
Keyword(s):  
Optimization Problem ◽  
Ad Hoc ◽  
Iterative Scheme ◽  
Tomographic Reconstruction ◽  
Region Of Interest ◽  
Projection Data ◽  
Reconstruction Problem ◽  
Convex Optimization Problem ◽  
Scanning Time ◽  
Novel Approach

Region of interest (ROI) tomography has gained increasing attention in recent years due to its potential to reducing radiation exposure and shortening the scanning time. However, tomographic reconstruction from ROI-focused illumination involves truncated projection data and typically results in higher numerical instability even when the reconstruction problem has unique solution. To address this problem, bothad hocanalytic formulas and iterative numerical schemes have been proposed in the literature. In this paper, we introduce a novel approach for ROI tomographic reconstruction, formulated as a convex optimization problem with a regularized term based on shearlets. Our numerical implementation consists of an iterative scheme based on the scaled gradient projection method and it is tested in the context of fan-beam CT. Our results show that our approach is essentially insensitive to the location of the ROI and remains very stable also when the ROI size is rather small.

scholarly journals Practical example for use of the supervised vicarious calibration (SVC) method on multisource hyperspectral imagery data – ValCalHyp airborne hyperspectral campaign under the EUFAR framework

2014 ◽  
Vol XL-7 ◽  
pp. 51-53
Author(s):  
A. Brook ◽  
E. Ben Dor
Keyword(s):  
Atmospheric Correction ◽  
Ground Truth ◽  
Critical Issue ◽  
Radiometric Calibration ◽  
Vicarious Calibration ◽  
Flight Direction ◽  
Novel Approach ◽  
Novel Method ◽  
General Goal ◽  
Cross Calibration

A novel approach for radiometric calibration and atmospheric correction of airborne hyperspectral (HRS) data, termed supervised vicarious calibration (SVC) was proposed by Brook and Ben-Dor in 2010. The present study was aimed at validating this SVC approach by simultaneously using several different airborne HSR sensors that acquired HSR data over several selected sites at the same time. The general goal of this study was to apply a cross-calibration approach to examine the capability and stability of the SVC method and to examine its validity. This paper reports the result of the multi sensors campaign took place over Salon de Provenance, France on behalf of the ValCalHyp project took place in 2011. The SVC method enabled the rectification of the radiometric drift of each sensor and improves their performance significantly. The flight direction of the SVC targets was found to be a critical issue for such correction and recommendations have been set for future utilization of this novel method. The results of the SVC method were examined by comparing ground-truth spectra of several selected validation targets with the image spectra as well as by comparing the classified water quality images generated from all sensors over selected water bodies.

Correlation between near-surface electromagnetic soil parameters and early-time GPR signals: An experimental study

Geophysics ◽  
2007 ◽  
Vol 72 (2) ◽  
pp. A25-A28 ◽  
Author(s):  
Elena Pettinelli ◽  
Giuliano Vannaroni ◽  
Barbara Di Pasquo ◽  
Elisabetta Mattei ◽  
Andrea Di Matteo ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Early Time ◽  
Test Site ◽  
Time Domain Reflectometry ◽  
Soil Parameters ◽  
Time Interval ◽  
Near Surface ◽  
Novel Approach ◽  
Natural Test ◽  
Ground Penetrating

We explore a new approach to evaluate the effect of soil electromagnetic parameters on early-time ground-penetrating radar (GPR) signals. The analysis is performed in a time interval which contains the direct airwaves and ground waves, propagating between transmitting and receiving antennas. To perform the measurements we have selected a natural test site characterized by very strong lateral gradient of the soil electrical properties. To evaluate the effect of the subsoil permittivity and conductivity on the radar response we compare the envelope amplitude of the GPR signals received in the first [Formula: see text] within [Formula: see text]-wide windows, with the electrical properties ([Formula: see text] and [Formula: see text]) determined using time-domain reflectometry (TDR). The results show that the constitutive soil parameters strongly influence early-time signals, suggesting a novel approach for estimating the spatial variability of water content with GPR.

Quantitative conductivity and permittivity estimation using full-waveform inversion of on-ground GPR data

Geophysics ◽  
2012 ◽  
Vol 77 (6) ◽  
pp. H79-H91 ◽  
Author(s):  
Sebastian Busch ◽  
Jan van der Kruk ◽  
Jutta Bikowski ◽  
Harry Vereecken
Keyword(s):  
Quantitative Estimation ◽  
Waveform Inversion ◽  
Measured Data ◽  
Optimization Approach ◽  
Full Waveform Inversion ◽  
Near Surface ◽  
Full Waveform ◽  
Novel Approach ◽  
Wide Range ◽  
Starting Model

Conventional ray-based techniques for analyzing common-midpoint (CMP) ground-penetrating radar (GPR) data use part of the measured data and simplified approximations of the reality to return qualitative results with limited spatial resolution. Whereas these methods can give reliable values for the permittivity of the subsurface by employing only the phase information, the far-field approximations used to estimate the conductivity of the ground are not valid for near-surface on-ground GPR, such that the estimated conductivity values are not representative for the area of investigation. Full-waveform inversion overcomes these limitations by using an accurate forward modeling and inverts significant parts of the measured data to return reliable quantitative estimates of permittivity and conductivity. Here, we developed a full-waveform inversion scheme that uses a 3D frequency-domain solution of Maxwell’s equations for a horizontally layered subsurface. Although a straightforward full-waveform inversion is relatively independent of the permittivity starting model, inaccuracies in the conductivity starting model result in erroneous effective wavelet amplitudes and therefore in erroneous inversion results, because the conductivity and wavelet amplitudes are coupled. Therefore, the permittivity and conductivity are updated together with the phase and the amplitude of the source wavelet with a gradient-free optimization approach. This novel full-waveform inversion is applied to synthetic and measured CMP data. In the case of synthetic single layered and waveguide data, where the starting model differs significantly from the true model parameter, we were able to reconstruct the obtained model properties and the effective source wavelet. For measured waveguide data, different starting values returned the same wavelet and quantitative permittivities and conductivities. This novel approach enables the quantitative estimation of permittivity and conductivity for the same sensing volume and enables an improved characterization for a wide range of applications.

A novel approach to estimating near‐surface S‐wave velocity and converted‐wave receiver statics

2009 ◽  
Author(s):  
Rishi Bansal ◽  
Warren Ross ◽  
Sunwoong Lee ◽  
Mike Matheney ◽  
Alex Martinez ◽  
...  
Keyword(s):  
Wave Velocity ◽  
S Wave ◽  
Converted Wave ◽  
Near Surface ◽  
Novel Approach

Correction Method for Ion Yield Transients in the Near Surface Region of Sims Depth Profiles

1985 ◽  
Vol 54 ◽  
Author(s):  
S. R. Bryan ◽  
R. W. Linton ◽  
D. P. Griffis
Keyword(s):  
Steady State ◽  
Secondary Ion Mass Spectrometry ◽  
High Sensitivity ◽  
Depth Resolution ◽  
Surface Region ◽  
Correction Method ◽  
Ion Concentration ◽  
Near Surface ◽  
Ion Yields ◽  
Secondary Ion

As solid state device features continue to decrease in size, it has become more important to characterize dopant concentrations within the first several hundred angstroms of the surface. Secondary ion mass spectrometry (SIMS) is the technique of choice for dopant depth profiling due to its high sensitivity and good depth resolution. In order to increase the sensitivity of SIMS, electropositive elements (e.g. oxygen) or electronegative elements (e.g. cesium) are used as primary ion species to enhance positive or negative secondary ion yields, respectively. This has the disadvantage, however, of causing secondary ion yields to vary by up to several orders of magnitude over the first few hundred angstroms of a depth profile as the implanted primary ion concentration increases [1,2]. Secondary ion yields stabilize once the primary ion reaches a steady state concentration, which occurs at a depth proportional to the range of the primary ions in the solid. This ion yield transient artifact hinders quantification of dopant concentrations until the primary ion concentration reaches steady state.

Investigation of Oxidation Process of Ultrathin Amorphous and/or Nano-Crystalline Silicon Films

2002 ◽  
Vol 727 ◽  
Author(s):  
R. Mu ◽  
M. Wu ◽  
Y.C. Liu ◽  
A. Ueda ◽  
D.O. Henderson ◽  
...  
Keyword(s):  
Oxidation Process ◽  
Crystalline Silicon ◽  
Surface Oxidation ◽  
Calibration Procedure ◽  
Temperature Cycling ◽  
Experimental Calibration ◽  
Near Surface ◽  
Nano Crystalline ◽  
Ambient Oxygen ◽  
Two Stages

AbstractA series experiments were conducted and reported here on how to employ quartz crystal microbalance (QCM) as a highly mass sensitive sensor to study a-Si film and Si nanocrystals oxidation under ambient oxygen. An experimental calibration procedure has been developed to prevent problems with QCM systems during routine study. With the help of pulsed laser deposition (PLD) technique, one can purposely deposit a thin layer of a heavy element as an insitu calibrant which can be analyzed by RBS quantitatively for QCM. The errors resulted from manufacture's sensor, non-repeatable sensor mounting and handling, temperature cycling history from run to run and so on will be effectively eliminated. Our preliminary results indicate that the oxidation process of a-Si thin films has two stages. A fast oxidation associated with surface and near surface oxidation followed by a slow oxidation. The former is depends on the oxygen vapor pressure in the chamber and the later is oxygen diffusion controlled process.

Skin Color Correction for Tissue Spectroscopy: Demonstration of a Novel Approach with Tissue-Mimicking Phantoms

2005 ◽  
Vol 59 (2) ◽  
pp. 237-244 ◽  
Author(s):  
Olusola O. Soyemi ◽  
Michelle R. Landry ◽  
Ye Yang ◽  
Patrick O. Idwasi ◽  
Babs R. Soller
Keyword(s):  
Skin Color ◽  
Near Infrared ◽  
Skin Pigmentation ◽  
Nir Spectroscopy ◽  
Bottom Layer ◽  
Correction Method ◽  
Color Variation ◽  
Absorption Properties ◽  
Novel Approach ◽  
Components Analysis

The application of partial least squares (PLS) regression to visible–near-infrared (VIS-NIR) spectroscopy for modeling important blood and tissue parameters is generally complicated by the variation in skin pigmentation (melanin) across the human population. An orthogonal correction method for removing the influence of skin pigmentation has been demonstrated in diffuse reflectance spectra from two-layer tissue-mimicking phantoms. The absorption properties of the phantoms were defined by lyophilized human hemoglobin (bottom layer) and synthetic melanin (top layer). Tissue-like scattering was simulated in both layers with intralipid™. The approach uses principal components analysis (PCA) loading vectors from a separate set of phantom spectra that encode the unwanted melanin variation to remove the effect of melanin from the test phantoms. The preprocessing of phantom spectra using this orthogonal correction method resulted in PLS models with reduced complexity and enhanced prediction performance. Preliminary results from a separate study that evaluates the feasibility of defining skin color variation in an experiment with a single human subject are also presented.

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