65 research outputs found
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
A microsatellite marker for yellow rust resistance in wheat
Bulk segregant analysis (BSA) was used to identify molecular markers associated with yellow rust disease resistance in wheat (Triticum aestivum L.). DNAs isolated from the selected yellow rust tolerant and susceptible F-2 individuals derived from a cross between yellow rust resistant and susceptible wheat genotypes were used to established a "tolerant" and a "susceptible" DNA pool. The BSA was then performed on these DNA pools using 230 markers that were previously mapped onto the individual wheat chromosomes. One of the SSR markers (Xgwm382) located on chromosome group 2 (A, B, D genomes) was present in the resistant parent and the resistant bulk but not in the susceptible parent and the susceptible bulk, suggesting that this marker is linked to a yellow rust resistance gene. The presence of Xgwm382 was also tested in 108 additional wheat genotypes differing in yellow rust resistance. This analysis showed that 81% of the wheat genotypes known to be yellow rust resistant had the Xgwm382 marker, further suggesting that the presence of this marker correlates with yellow rust resistance in diverse wheat germplasm. Therefore, Xgwm382 could be useful for marker assisted selection of yellow rust resistances genotypes in wheat breeding programs
BOUT++: a framework for parallel plasma fluid simulations
A new modular code called BOUT++ is presented, which simulates 3D fluid
equations in curvilinear coordinates. Although aimed at simulating Edge
Localised Modes (ELMs) in tokamak X-point geometry, the code is able to
simulate a wide range of fluid models (magnetised and unmagnetised) involving
an arbitrary number of scalar and vector fields, in a wide range of geometries.
Time evolution is fully implicit, and 3rd-order WENO schemes are implemented.
Benchmarks are presented for linear and non-linear problems (the Orszag-Tang
vortex) showing good agreement. Performance of the code is tested by scaling
with problem size and processor number, showing efficient scaling to thousands
of processors.
Linear initial-value simulations of ELMs using reduced ideal MHD are
presented, and the results compared to the ELITE linear MHD eigenvalue code.
The resulting mode-structures and growth-rate are found to be in good agreement
(BOUT++ = 0.245, ELITE = 0.239). To our knowledge, this is the first time
dissipationless, initial-value simulations of ELMs have been successfully
demonstrated.Comment: Submitted to Computer Physics Communications. Revised to reduce page
count. 18 pages, 16 figure
Evidence of psi(3770) non-DD-bar Decay to J/psi pi+pi-
Evidence of decays to a non- final state is
observed. A total of \psi(3770) \to \PPJP events are
obtained from a data sample of 27.7 taken at center-of-mass
energies around 3.773 GeV using the BES-II detector at the BEPC. The branching
fraction is determined to be BF(\psi(3770) \to \PPJP)=(0.34\pm 0.14 \pm
0.09)%, corresponding to the partial width of \Gamma(\psi(3770) \to \PPJP) =
(80 \pm 33 \pm 23) keV.Comment: 8 pages, 7 figures, Submitted to Physics Letters
Vision-based 3D Surface Motion Capture for the DIET Breast Cancer Screening System
Breast cancer is one of the most prevalent forms
of cancer in the world today. The search for effective treatment and screening methods is a highly active area of research. The Digital Image-based ElastoTomography (DIET) project is a new
breast cancer screening system under development, where surface motion from the mechanically actuated breast is measured in
3D, and used as input to an inverse problem solving for breast elasticity. Cancerous lesions appear as high contrast features,
being an order of magnitude stiffer than healthy tissue. The 3D motion capture is measured by an array of digital cameras using computer vision techniques. This paper presents
a computer vision imaging system for the capture of 3D breast surface motion for the DIET system, including the image acquisition
system, camera calibration, and 3D surface and motion reconstruction. Results are presented for experiments performed with silicone gel phantoms, with conditions designed to replicate the clinical procedure. Full 3D surface motion is successfully captured using an array of 5 cameras. Some successful results from the DIET inverse problem are also presented to demonstrate the viability of the system in practice
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
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