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Oxford, United Kingdom

Tromans C.,University of Oxford | Cocker M.,University of Oxford | Brady S.M.,Old Road Campus Research Building
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012

Digital x-ray acquisition allows the sophisticated processing of acquired images before display to the reader, making possible such operations as the removal in software of the systematic blurring effect of scatter. A method for analysing scatter removal is presented. The scatter model incorporated within the Standard Attenuation Rate (SAR) is used, which is a method for calculating a normalised image of tissue radiodensity. The model builds on the fundamental physical relations underlying Monte Carlo techniques; but through optimal information sampling and interpolation is able to execute in a clinically realistic time. The scatter kernel arising around each primary ray is calculated, and these are superimposed to give the scatter image. An iterative refinement procedure is used to calculate the radiodensity and scatter at each ray/pixel, cyclically feeding back to each other, to yield the scatter field. Image sharpness and contrast-to-noise (CNR) analysis is presented for two tissue equivalent phantoms. The algorithm is found to be able to match image sharpness without the grid, to that with the grid present, confirmed by residual analysis using autocorrelation plots which show the difference is almost white noise within a 95% C.I. The increased fluence in the absence of the grid is shown to allow dose to be reduced by 37-49%, whilst delivering equivalent contrast and CNR. © 2012 Springer-Verlag Berlin Heidelberg. Source


Tromans C.,University of Oxford | Brady S.M.,Old Road Campus Research Building
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012

Breast density is a key component of risk assessment for personalised screening, necessitating robust, repeatable measures. The Standard Attenuation Rate (SAR) enables the quantification of breast tissue radiodensity at each pixel, relative to the attenuation of a reference material, so may be used as a measure of volumetric breast density. A major complication is quantification of tissue in the periphery of the breast, the (often substantial) region between the skin boundary and the point at which the breast occupies the entire distance between the plates, since the thickness is governed by the shape of the compressed breast, rather than the separation of the plates. We present a method to measure the compressed shape from the image, hence the thickness at each point in the periphery. The method exploits the vastly different attenuation of the various breast tissues from that of air, and uses spatial smoothing to glean a signal estimating solely the underlying thickness. An iterative refinement procedure allows for variation in scatter in the periphery arising from the air boundary edge effects. The outcome of the inclusion of the periphery in breast density quantified by this method is analysed, and the importance of this region's inclusion illustrated. © 2012 Springer-Verlag Berlin Heidelberg. Source


Tromans C.E.,University of Oxford | Cocker M.R.,University of Oxford | Brady S.M.,Old Road Campus Research Building
Physics in Medicine and Biology | Year: 2012

We present an efficient method to calculate the primary and scattered x-ray photon fluence component of a mammographic image. This can be used for a range of clinically important purposes, including estimation of breast density, personalized image display, and quantitative mammogram analysis. The method is based on models of: the x-ray tube; the digital detector; and a novel ray tracer which models the diverging beam emanating from the focal spot. The tube model includes consideration of the anode heel effect, and empirical corrections for wear and manufacturing tolerances. The detector model is empirical, being based on a family of transfer functions that cover the range of beam qualities and compressed breast thicknesses which are encountered clinically. The scatter estimation utilizes optimal information sampling and interpolation (to yield a clinical usable computation time) of scatter calculated using fundamental physics relations. A scatter kernel arising around each primary ray is calculated, and these are summed by superposition to form the scatter image. Beam quality, spatial position in the field (in particular that arising at the air-boundary due to the depletion of scatter contribution fromthe surroundings), and the possible presence of a grid, are considered, as is tissue composition using an iterative refinement procedure. We present numerous validation results that use a purpose designed tissue equivalent step wedge phantom. The average differences between actual acquisitions and modelled pixel intensities observed across the adipose to fibroglandular attenuation range vary between 5% and 7%, depending on beam quality and, for a single beam quality are 2.09% and 3.36% respectively with and without a grid. © 2012 Institute of Physics and Engineering in Medicine. Source


Tromans C.E.,University of Oxford | Cocker M.R.,University of Oxford | Brady S.M.,Old Road Campus Research Building
Physics in Medicine and Biology | Year: 2012

The analysis of (x-ray) mammograms remains qualitative, relying on the judgement of clinicians. We present a novel method to compute a quantitative, normalized measure of tissue radiodensity traversed by the primary beam incident on each pixel of a mammogram, a measure we term the standard attenuation rate (SAR). SAR enables: the estimation of breast density which is linked to cancer risk; direct comparison between images; the full potential of computer aided diagnosis to be utilized; and a basis for digital breast tomosynthesis reconstruction. It does this by removing the effects of the imaging conditions under which the mammogram is acquired. First, the x-ray spectrum incident upon the breast is calculated, and from this, the energy exiting the breast is calculated. The contribution of scattered radiation is calculated and subtracted. The SAR measure is the scaling factor that must be applied to the reference material in order to match the primary attenuation of the breast. Specifically, this is the scaled reference material attenuation which when traversed by an identical beam to that traversing the breast, and when subsequently detected, results in the primary component of the pixel intensity observed in the breast image. We present results using two tissue equivalent phantoms, as well as a sensitivity analysis to detector response changes over time and possible errors in compressed thickness measurement. © 2012 Institute of Physics and Engineering in Medicine. Source


Morley A.D.,University of Dundee | Pugliese A.,Beatson Institute for Cancer Research | Birchall K.,Medical Research Council Technology | Bower J.,Beatson Institute for Cancer Research | And 12 more authors.
Drug Discovery Today | Year: 2013

The identification of high-quality hits during the early phases of drug discovery is essential if projects are to have a realistic chance of progressing into clinical development and delivering marketed drugs. As the pharmaceutical industry goes through unprecedented change, there are increasing opportunities to collaborate via pre-competitive networks to marshal multifunctional resources and knowledge to drive impactful, innovative science. The 3D Fragment Consortium is developing fragment-screening libraries with enhanced 3D characteristics and evaluating their effect on the quality of fragment-based hit identification (FBHI) projects. © 2013 Elsevier Ltd. All rights reserved. Source

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