scholarly journals Elastography Method for Reconstruction of Nonlinear Breast Tissue Properties

2009 ◽  
Vol 2009 ◽  
pp. 1-9 ◽  
Author(s):  
Z. G. Wang ◽  
Y. Liu ◽  
G. Wang ◽  
L. Z. Sun
Keyword(s):  
Breast Tissue ◽  
Three Dimensional ◽  
Material Model ◽  
Nonlinear Material ◽  
Fatty Tissue ◽  
Nonlinear Method ◽  
Tissue Properties ◽  
Breast Cancer Study ◽  
Breast Phantom ◽  
The Difference

Elastography is developed as a quantitative approach to imaging linear elastic properties of tissues to detect suspicious tumors. In this paper a nonlinear elastography method is introduced for reconstruction of complex breast tissue properties. The elastic parameters are estimated by optimally minimizing the difference between the computed forces and experimental measures. A nonlinear adjoint method is derived to calculate the gradient of the objective function, which significantly enhances the numerical efficiency and stability. Simulations are conducted on a three-dimensional heterogeneous breast phantom extracting from real imaging including fatty tissue, glandular tissue, and tumors. An exponential-form of nonlinear material model is applied. The effect of noise is taken into account. Results demonstrate that the proposed nonlinear method opens the door toward nonlinear elastography and provides guidelines for future development and clinical application in breast cancer study.

scholarly journals Nonlinear Elasto-Mammography for Characterization of Breast Tissue Properties

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Z. G. Wang ◽  
Y. Liu ◽  
G. Wang ◽  
L. Z. Sun
Keyword(s):  
Three Dimensional ◽  
Computational Prediction ◽  
Fatty Tissue ◽  
Tissue Properties ◽  
X Ray ◽  
Mechanical Responses ◽  
Breast Phantom ◽  
The Difference ◽  
Breast Tissues

Quantification of the mechanical behavior of normal and cancerous tissues has important implication in the diagnosis of breast tumor. The present work extends the authors' nonlinear elastography framework to incorporate the conventional X-ray mammography, where the projection of displacement information is acquired instead of full three-dimensional (3D) vector. The elastic parameters of normal and cancerous breast tissues are identified by minimizing the difference between the measurement and the corresponding computational prediction. An adjoint method is derived to calculate the gradient of the objective function. Simulations are conducted on a 3D breast phantom consisting of the fatty tissue, glandular tissue, and cancerous tumor, whose mechanical responses are hyperelastic in nature. The material parameters are identified with consideration of measurement error. The results demonstrate that the projective displacements acquired in X-ray mammography provide sufficient constitutive information of the tumor and prove the usability and robustness of the proposed method and algorithm.

scholarly journals Collapse Analysis of ERW Pipe Based on Roll-Forming and Sizing Simulations

2019 ◽  
Vol 7 (11) ◽  
pp. 410 ◽  
Author(s):  
Seong-Wook Han ◽  
Yeun Chul Park ◽  
Soo-Chang Kang ◽  
Sungmoon Jung ◽  
Ho-Kyung Kim
Keyword(s):  
Residual Stress ◽  
Limit State ◽  
Three Dimensional ◽  
Material Model ◽  
Nonlinear Material ◽  
Roll Forming ◽  
Two Factors ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Api 5L X70 Steel

The demand for electric resistance welded (ERW) pipe for deep-water installation has increased, which necessitates a higher degree of accuracy in evaluating the strength of pipe in order to satisfy the design limit state, otherwise referred to as the collapse performance. Since ovality and residual stress governs the collapse performance, an accurate evaluation of these factors is needed. An analytical approach using a three-dimensional finite element method was proposed to simulate the roll-forming and sizing processes in manufacturing ERW pipe. To simulate significant plastic deformation during manufacturing, a nonlinear material model that included the Bauschinger effect was incorporated. The manufacturing of ERW pipe made of API 5L X70 steel was simulated and analyzed for collapse performance. Controlling the ovality of the pipe significantly decreased the amount of pressure that would cause a collapse, whereas the effect of residual stress was minor. These two factors could be improved via the use of a proper sizing ratio.

scholarly journals In-Silico study of microwave ablation applicators of different size for breast cancer treatment

2020 ◽  
Vol 21 (3) ◽  
pp. 1-13
Author(s):  
José Irving Hernández Jacquez ◽  
Mario Francisco Jesús Cepeda Rubio ◽  
Geshel David Guerrero López ◽  
Arturo Vera Hernández ◽  
Lorenzo Leija Salas ◽  
...  
Keyword(s):  
Breast Cancer ◽  
In Silico ◽  
Microwave Ablation ◽  
Breast Tissue ◽  
Treatment Options ◽  
Coaxial Cable ◽  
Invasive Technique ◽  
In Silico Study ◽  
Breast Phantom ◽  
The Difference

Breast cancer is one of the most common types of cancer in females around the world, surgery is the preferred treatment for this disease in early stages, however there are some emergent treatment options with less clinical and cosmetically repercussions, being one of these the microwave ablation. Microwave ablation is a minimally invasive technique used to treat tumors in different organs of the human body, mainly in liver, lung and kidney. It consist on the destruction of the tumor by rising the temperature of the cells until necrosis is achieve. In breast tumors, this technique has been rarely used in human patients. Depending on the type of tissue, an applicator must be made to be coupled to ensure that energy used is not reflected, so the standing wave ratio is closest to 1. In order to determine an appropriate design for the applicators that could be used for the treatment of breast cancer, an in-silico study of microwave ablation of breast cancer was made to show the difference between micro-coaxial applicators constructed with two different types of coaxial cable (UT-47 and UT-85) utilizing the same design in three possible scenarios breast tissue, tumor tissue and tumor surrounded by breast tissue. The simulation was realized using COMSOL Multiphysics commercial software, due to its capabilities to simulate the electromagnetics and thermals effects. A slot type applicator was selected because of its ease of manufacture and the available literature on it. The results shows a better coupling for the applicator constructed with the UT-47 cable, especially in the tumor phantom surrounded by breast phantom test.

Defocus ramp correction in spot-scan imaging

1992 ◽  
Vol 50 (1) ◽  
pp. 130-131
Author(s):  
Kenneth H. Downing
Keyword(s):  
Computer Control ◽  
Three Dimensional ◽  
Sufficient Accuracy ◽  
Objective Lens ◽  
Electron Crystallography ◽  
Contrast Transfer Function ◽  
Tilt Axis ◽  
Specimen Height ◽  
The Difference ◽  
Envelope Functions

Three-dimensional structures of a number of samples have been determined by electron crystallography. The procedures used in this work include recording images of fairly large areas of a specimen at high tilt angles. There is then a large defocus ramp across the image, and parts of the image are far out of focus. In the regions where the defocus is large, the contrast transfer function (CTF) varies rapidly across the image, especially at high resolution. Not only is the CTF then difficult to determine with sufficient accuracy to correct properly, but the image contrast is reduced by envelope functions which tend toward a low value at high defocus.We have combined computer control of the electron microscope with spot-scan imaging in order to eliminate most of the defocus ramp and its effects in the images of tilted specimens. In recording the spot-scan image, the beam is scanned along rows that are parallel to the tilt axis, so that along each row of spots the focus is constant. Between scan rows, the objective lens current is changed to correct for the difference in specimen height from one scan to the next.

The iron content of iron superoxide dismutase: determination by anomalous scattering

1983 ◽  
Vol 218 (1210) ◽  
pp. 119-126 ◽  
Keyword(s):  
Superoxide Dismutase ◽  
Iron Content ◽  
Three Dimensional ◽  
Anomalous Scattering ◽  
Total Iron Content ◽  
Iron Site ◽  
Iron Superoxide Dismutase ◽  
Density Map ◽  
The Difference ◽  
Electron Density Map

The number of iron atoms in the dimeric iron-containing superoxide dismutase from Pseudomonas ovalis and their atomic positions have been determined directly from anomalous scattering measurements on crystals of the native enzyme. To resolve the long-standing question of the total amount of iron per molecule for this class of dismutase, the occupancy of each site was refined against the measured Bijvoet differences. The enzyme is a symmetrical dimer with one iron site in each subunit. The iron position is 9 ņ from the intersubunit interface. The total iron content of the dimer is 1.2±0.2 moles per mole of protein. This is divided between the subunits in the ratio 0.65:0.55; the difference between them is probably not significant. Since each subunit contains, on average, slightly more than half an iron atom we conclude that the normal state of this enzyme is two iron atoms per dimer but that some of the metal is lost during purification of the protein. Although the crystals are obviously a mixture of holo- and apo-enzymes, the 2.9 Å electron density map is uniformly clean, even at the iron site. We conclude that the three-dimensional structures of the iron-bound enzyme and the apoenzyme are identical.

scholarly journals SPECTRAL CORRELATIONS IN DISORDERED MESOSCOPIC METALS AND THEIR RELEVANCE FOR PERSISTENT CURRENTS

1996 ◽  
Vol 10 (28) ◽  
pp. 1397-1406 ◽  
Author(s):  
AXEL VÖLKER ◽  
PETER KOPIETZ
Keyword(s):  
Energy Levels ◽  
Three Dimensional ◽  
Average Density ◽  
Electron Interaction ◽  
Energy Window ◽  
Persistent Currents ◽  
Dependent Part ◽  
The Difference ◽  
Aharonov Bohm ◽  
Grand Canonical

We use the Lanczos method to calculate the variance σ2(E, ϕ) of the number of energy levels in an energy window of width E below the Fermi energy for noninteracting disordered electrons on a thin three-dimensional ring threaded by an Aharonov–Bohm flux ϕ. We confirm numerically that for small E the flux-dependent part of σ2(E, ϕ) is well described by the Altshuler–Shklovskii-diagram involving two Cooperons. However, in the absence of electron–electron interactions this result cannot be extrapolated to energies E where the energy-dependence of the average density of states becomes significant. We discuss consequences for persistent currents and argue that for the calculation of the difference between the canonical- and grand canonical current it is crucial to take the electron–electron interaction into account.

Stresses in Ultrasonically Assisted Turning

2006 ◽  
Vol 5-6 ◽  
pp. 351-358 ◽  
Author(s):  
N. Ahmed ◽  
A.V. Mitrofanov ◽  
Vladimir I. Babitsky ◽  
Vadim V. Silberschmidt
Keyword(s):  
Ultrasonic Vibration ◽  
Vibration Frequency ◽  
Cutting Forces ◽  
Plastic Material ◽  
Process Zone ◽  
Three Dimensional ◽  
Rate Sensitivity ◽  
High Strength ◽  
Material Model ◽  
Shear Stresses

Ultrasonically assisted turning (UAT) is a novel material-processing technology, where high frequency vibration (frequency f ≈ 20kHz, amplitude a ≈15μm) is superimposed on the movement of the cutting tool. Advantages of UAT have been demonstrated for a broad spectrum of applications. Compared to conventional turning (CT), this technique allows significant improvements in processing intractable materials, such as high-strength aerospace alloys, composites and ceramics. Superimposed ultrasonic vibration yields a noticeable decrease in cutting forces, as well as a superior surface finish. A vibro-impact interaction between the tool and workpiece in UAT in the process of continuous chip formation leads to a dynamically changing stress distribution in the process zone as compared to the quasistatic one in CT. The paper presents a three-dimensional, fully thermomechanically coupled computational model of UAT incorporating a non-linear elasto-plastic material model with strain-rate sensitivity and contact interaction with friction at the chip–tool interface. 3D stress distributions in the cutting region are analysed for a representative cycle of ultrasonic vibration. The dependence of various process parameters, such as shear stresses and cutting forces on vibration frequency and amplitude is also studied.

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