Specialised Image Capture Systems for a DIET Breast Cancer Screening System

Digital Image-based Elasto-Tomography (DIET) is an emerging technology for non-invasive breast cancer screening. This technology actuates breast tissue and measures the surface motion using digital imaging technology. The internal distribution of stiffness is then reconstructed using Boundary Element or Finite Element Methods (FEM or BEM). However, obtaining accurate imaging at high frequency and high resolution in terms of numbers of pixels is challenging if enough accuracy is to be obtained in the motion sensing to deliver a useful result. The overall focus of such mechatronic and digitally centred systems is on providing a low-cost, radiation dose-free and portable screening system capable of screening numerous patients per day – in direct contrast to current low throughput, non-portable and high cost x-ray and MRI based approaches. Thus, DIET technology relies on obtaining high resolution images of a breasts surface under high frequency actuation, typically in the range of 50-100Hz. Off-the-shelf digital cameras and imaging elements are unable to capture images directly at these speeds. A method is presented for obtaining the required high speed image capture at a resolution of 1280x1024 pixels and actuation frequency of 100Hz. The prototype apparatus presented uses two imaging sensors in combination with frame grabbers and a dSpace™ control system, to produce an automated image capture system. The system integrates a precision controlled strobe lighting system to selectively capture sinusoids at different points in the sinusoidal cycle of response. The final working system produced images that enabled effective 3D motion tracking of the surface of a silicon phantom actuated at 100Hz. The surface of the phantom was strobed at pre-selected phases from 0 to 360 degrees, and an image was captured for each phase. The times at which image capture occurred were calculated for a phase lag increment of 10 degrees resulting in an image effectively every 0.00028s for the actuator cycle of 0.01s. The comparison of the actual trigger times and pre-selected ideal trigger times gave a mean absolute error of 1.4%, thus demonstrating the accuracy of the final system. Final validation is performed using this system to track motion in a silicon gel phantom. The motion is tracked accurately using a novel Euclidean Invariant signature method. Both cameras delivered similar results with over 90% of points tracked to within 1-2%. This level of accuracy confirms the ability to effectively accurately reconstruct the stiffness as validated in other related studies

Expanding and Collapsing Scalar Field Thin Shell

This paper deals with the dynamics of scalar field thin shell in the Reissner-Nordstr$\ddot{o}$m geometry. The Israel junction conditions between Reissner-Nordstr$\ddot{o}$m spacetimes are derived, which lead to the equation of motion of scalar field shell and Klien-Gordon equation. These equations are solved numerically by taking scalar field model with the quadratic scalar potential. It is found that solution represents the expanding and collapsing scalar field shell. For the better understanding of this problem, we investigate the case of massless scalar field (by taking the scalar field potential zero). Also, we evaluate the scalar field potential when $p$ is an explicit function of $R$. We conclude that both massless as well as massive scalar field shell can expand to infinity at constant rate or collapse to zero size forming a curvature singularity or bounce under suitable conditions.Comment: 15 pages, 11 figure

The Theory of Brown Dwarfs and Extrasolar Giant Planets

Straddling the traditional realms of the planets and the stars, objects below the edge of the main sequence have such unique properties, and are being discovered in such quantities, that one can rightly claim that a new field at the interface of planetary science and and astronomy is being born. In this review, we explore the essential elements of the theory of brown dwarfs and giant planets, as well as of the new spectroscopic classes L and T. To this end, we describe their evolution, spectra, atmospheric compositions, chemistry, physics, and nuclear phases and explain the basic systematics of substellar-mass objects across three orders of magnitude in both mass and age and a factor of 30 in effective temperature. Moreover, we discuss the distinctive features of those extrasolar giant planets that are irradiated by a central primary, in particular their reflection spectra, albedos, and transits. Aspects of the latest theory of Jupiter and Saturn are also presented. Throughout, we highlight the effects of condensates, clouds, molecular abundances, and molecular/atomic opacities in brown dwarf and giant planet atmospheres and summarize the resulting spectral diagnostics. Where possible, the theory is put in its current observational context.Comment: 67 pages (including 36 figures), RMP RevTeX LaTeX, accepted for publication in the Reviews of Modern Physics. 30 figures are color. Most of the figures are in GIF format to reduce the overall size. The full version with figures can also be found at: http://jupiter.as.arizona.edu/~burrows/papers/rm

Advanced Semi-Active Resetable Devices and Device Modeling Including Non-Linearities

Resetable devices are a novel semi-active approach to managing structural response energy. Recently developed devices allow independent control of each chamber enabling unique approaches to sculpting the structural hysteresis loops and behaviour. This paper creates a non-linear model of experimental prototypes that is fully generalisable, and does so in a step-by-step fashion adding each non-linear affect individually. Non-linearities that can significantly affect performance, including valve size, mass flow rate and friction are characterised experimentally and modeled. The results are validated against experimental data for cases of all forms of device control, as well as for several experimental cases utilizing external pressurized sources to enhance the force capacity. Force capacity, using a pressurised reservoir and/or accumulator increased force capacity of these devices from 100-600%, increasing the potential of these designs and approach to seismic energy dissipation. Final model results have less than 5% error compared to nonlinear experimental data. There is a strong correlation between the fundamental nonlinear dynamics modelled and the experimental results, validating the overall model and approach. The overall results and approach are fully general for application to the design or analysis of similar device systems

Application of Sensing & Actuation for Online Hybrid Testing of Structural Control Devices

On-line hybrid tests couple virtual structures under dynamic loading with physical sub-structures or devices in a dynamic test rig. The use of sensors and actuators in a closed-loop feedback system maintains the dynamic equilibrium of the overall system comprising the physical test article and virtual modelled structure. This research presents simple, cost-effective and robust hybrid test system by cleverly melding the sensors and actuators with virtual model. It outlines solutions to the major issues faced in developing any hybrid system. The overall approach is centred on the dSpaceTM real-time control system development tool

Strobe Imaging System for Digital Image-based Elasto-Tomography Breast Cancer Screening

Digital Image-based Elasto-Tomography (DIET) technology relies on obtaining high resolution images of a breasts surface under high frequency actuation, typically in the range of 50-100Hz. Off-the-shelf digital cameras and imaging elements are unable to capture images directly at these speeds. A method based on strobe imaging is presented for obtaining the required high speed image capture at a resolution of 1280x1024 pixels and actuation frequency of 100 Hz. The final working system produced images that enabled effective 3D motion tracking of the surface of a silicon phantom. The motion is tracked accurately using a novel Euclidean Invariant signature method

Digital image-based elasto-tomography: first experiments in surface based mechanical property estimation of gelatine phantoms

Invited special edition on Bio-EngineeringDigital Image-based Elasto-Tomography (DIET) is a novel surface-based elasticity reconstruction method for determining the elastic property distribution within the breast. Following on from proof of concept simulation studies, this research considers the motion evaluation and stiffness reconstruction of a soft tissue approximating gelatine phantom. This initial phantom work provides an intermediate stage between prior simulation studies more detailed phantom studies to follow. Reference points on the surface of a cylindrical phantom were successfully tracked and converted into a steady-state motion description. Motion error based mechanical property reconstruction allowed an estimation of the stiffness of the gelatine when actuated at 50 Hz. The reconstructed stiffness compared favorably with independently measured stiffness properties of the gelatine material when experimental assumptions were considered. An experimental noise estimate of 50% was confirmed accurate by comparing experimental motions to simulated motion data with added noise

Re-Shaping Hysteresis: Seismic Semi-Active Control Experiments for a 1/5th Scale Structure

Semi-active resetable devices can improve seismic response. Novel 2-4 devices independently control each device chamber to customise structural hysteresis loops to reduce both displacement and base shear demands. Here, 2-4 devices are experimentally validated on a one-fifth scale test structure weighing 35kN with a natural period of 0.6 seconds. Four seismic inputs over a wide range of intensity levels are use in 27 tests. Results for resetable semi-active devices that modify hysteretic behaviour using different control laws are compared to spectral response analyses that predict ~30-50% peak displacement reductions. Fully uncontrolled tests were also done for lower intensity ground motions, along with fail-safe valves-open tests. Results show 25-50% peak displacement reductions compared to the valves open case, depending on the semi-active control law used and matching spectral analysis results. Additionally, a semi-active control law designed to simultaneously reduce base shear reduces it 10-20%. In contrast, 10-20% increases are seen for other approaches, as predicted. Overall, these are the first large-scale tests of this type of novel resetable devices. The results validate prior simulation and spectral analyses, and clearly show the potential. Finally, semi-active methods that re-shape hysteresis to control response and simultaneously limit base shear demand, are experimentally demonstrated for the first time

Experimental Validation of Semi-active Resetable Actuators in a 1/5th Scale Test Structure

The seismic performance of a test structure fitted with semi-active resetable devices is experimentally investigated. Shaking table tests are conducted on a 15 th scale four-storey building using 27 earthquake records at different intensity scalings. Different resetable device control laws result in unique hysteretic responses from the devices and thus the structure. This device adaptability enables manipulation or sculpting of the overall hysteresis response of the structure to address specific structural cases and types. The response metrics are presented as maximum 3rd floor acceleration and displacement, and the total base shear. The devices reduce all the response metrics compared with the uncontrolled case and a fail-safe surrogate. Cumulative probability functions allow comparison between different control laws and additionally allow tradeoffs in design to be rapidly assessed. Ease of changing the control law in real-time during an earthquake record further improves the adaptability of the system to obtain the optimum device response for the input motion and structural type. The findings are an important step to realizing full-scale structural control with customized semi-active hysteretic behaviour using these novel resetable device designs