Browsing by Author "Healy, Matthew J. F."
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Item Open Access 3D-printed coded apertures for x-ray backscatter radiography(SPIE, 2017-09-07) Munoz, Andre Arelius Marcus; Vella, Anna; Healy, Matthew J. F.; Lane, David W.; Jupp, Ian; Lockley, D.Many different mask patterns can be used for X-ray backscatter imaging using coded apertures, which can find application in the medical, industrial and security sectors. While some of these patterns may be considered to have a self-supporting structure, this is not the case for some of the most frequently used patterns such as uniformly redundant arrays or any pattern with a high open fraction. This makes mask construction difficult and usually requires a compromise in its design by drilling holes or adopting a no two holes touching version of the original pattern. In this study, this compromise was avoided by 3D printing a support structure that was then filled with a radiopaque material to create the completed mask. The coded masks were manufactured using two different methods, hot cast and cold cast. Hot casting involved casting a bismuth alloy at 80°C into the 3D printed acrylonitrile butadiene styrene mould which produced an absorber with density of 8.6 g cm-3. Cold casting was undertaken at room temperature, when a tungsten/epoxy composite was cast into a 3D printed polylactic acid mould. The cold cast procedure offered a greater density of around 9.6 to 10 g cm-3 and consequently greater X-ray attenuation. It was also found to be much easier to manufacture and more cost effective. A critical review of the manufacturing procedure is presented along with some typical images. In both cases the 3D printing process allowed square apertures to be created avoiding their approximation by circular holes when conventional drilling is used.Item Open Access An artificial X-ray wire test emitter and calculations on the resolution and field of view of X-ray pinhole optics by simulation(Elsevier, 2018-07-23) Vella, Anna; Munoz, Andre Arelius Marcus; Healy, Matthew J. F.; Lane, David W.; Lockley, DavidThe PENELOPE Monte Carlo simulation code was used to evaluate pinhole mask parameters for X-ray backscatter imaging in a security application. This work makes four major contributions: it describes a convenient efficient test object for evaluating X-ray optics, it converts the PENELOPE output into a simulated CCD image, it compactly outlines how image characteristics can be simply and reproducibly quantified, and it gives guidance on suitable materials and geometries for pinhole masks for X-ray imaging that could be applied to more complicated X-ray optics, such as coded masks. A novel test object X-ray emitter with the shape of a thin wire was specifically designed to explore the effect of mask material thickness and pinhole aperture diameter on image quality. Setting the test object to be the X-ray emitter rather than being a passive scatterer increases computational speed. The photon energy distribution of the artificial test object was set flat between selected energy limits to avoid the model being specific to any particular X-ray source technology. The modelled detector is an array of 1040 x 1392 pixels’ area detector inside a lead-lined camera housing. The pixelated detector was modelled by digitising the surface area represented by the PENELOPE phase space file and integrating the energies of the photons impacting each pixel with MATLAB code. The pinhole must be wide enough for sufficient field of view, whilst narrow enough for sufficient spatial resolution and the mask material needs to be thick enough to absorb most X-rays. When the mask material was too thick and the aperture too narrow, a collimation effect occurred. The consequence of excess collimation in a coded aperture is partial coding giving poor image reconstruction. Pure tungsten appears the most versatile material tested, where a 2 mm thickness and 2 mm aperture gives the most appropriate image characteristics for X-ray security imaging.Item Open Access Cost-effective approach to lung cancer risk for a radiological dispersal device (RDD) scenario(De Gruyter Open, 2019-12-11) Costa, Karolina P. S.; Lima, Sergio X.; Brum, Tercio; Lima, Zelmo R.; Amorim, Jose C. C.; Healy, Matthew J. F.; Vital, Helio C.; Prah, Matjaž; Andrade, Edson R.A release of radioactive material into the environment can lead to hazardous exposure of the population and serious future concerns about health issues such as an increased incidence of cancer. In this context, a practical methodology capable of providing useful basic information from the scenario can be valuable for immediate decisions and future risk assessment. For this work, the simulation of a radiological dispersal device (RDD) filled with americium-241 was considered. The radiation dose simulated by the HotSpot code was used as an input to the epidemiological equations from BEIR V producing the data used to assess the risk of lung cancer development. The methodology could be useful in providing training for responders aimed to the initial support addressed to decision-making for emergency response at the early phase of an RDD scenario. The results from the simulation allow estimating (a) the size of the potentially affected population, (b) the type of protection action considering gender and location of the individuals, (c) the absorbed doses, (d) the matrix of lung cancer incidence predictions over a period of 5 years, and (e) the cost-effectiveness in the initial decision environment.Item Open Access Derivation of a methodology to compare C,B and R detection capability in urban events(2016-08-10) Siong, R E T; Healy, Matthew J. F.Many comparisons have been made between Chemical detectors (C), between Biological (B) detectors, and between Radiological detectors (R), providing insights to the best C, B and R equipment for a given purpose. However, no comparison has been made between C, B and R systems to appraise how C, B and R detectors perform against each other and where capability gaps lie. The dissertation generates a method to achieve an inter-comparison between C, B and R detection capabilities and identifies where to invest resources to achieve a more effective overall CBR detection architecture. The inter-comparison methodology is based on an operational analysis tool (SMARTS). The overall CBR detection architecture is illustrated through detect to warn and detect to treat mechanisms across the timeline of a realistic scenario. The scenario has been created to be non-prejudicial to C, B or R incidents, deconstructed into four frames to accommodate SMARTS. The most suitable deconstruction is into early warning, personnel security screening, initial response and definitive identification frames. The most suitable detector Key Performance Characteristics (KPCs) are identified for each frame. SMARTS is performed by analysing the current performance of the C, B and R detection systems drawn from the literature and the target requirements determined by defensible logic. The desire to improve each capability from its current state to target requirement is subjectively determined by the author. A sensitivity analysis is applied to mitigate the effect of a limited pool of opinion. Applying the methodology to published CBR detection capability data and the author’s appraisal of the target requirement reveals that B detection requires the greatest development and R the least, and that detection in the security screening and initial response frames falls short of capability compared to early warning and definitive identification frames. Selectivity is a challenge across a broad range of frames and agents. This work provides a methodology that is modular and transparent so that it can be repopulated should new data or alternative perception arises.Item Open Access The development of x-ray backscatter imaging systema through simulation(2018-12) Vella, A.; Healy, Matthew J. F.X-ray backscatter has applications in defence and security, medical imaging, astrophysics and industry. The development and testing of X-ray backscatter imaging systems can be achieved not only by experiment, but also by using Monte-Carlo modelling. The PENELOPE simulation package was chosen for its versatility and transparency. However, PENELOPE is a radiation transport package that is not user-friendly, is not inherently compatible with parallel processing, and is not equipped with the facility to process output data in a way that replicates the output from imaging plates or energy dispersive detectors. Tools called PENMAT and PAXI were written in MATLAB to extend the capability of PENELOPE and so enable the efficient exploration of X-ray backscatter imaging which is the focus of this study. The enhanced PENELOPE suite was used to model a real thermionic source to validate the process by comparison with experiment, and model virtual sources suitable for exploring fundamental principles of backscatter. Virtual sources were conceived and designed to efficiently characterise various imaging system features. These include mono-directional and mono-energetic sources (to isolate energy dependant scattering cross sections), flat spectrum sources (to objectively characterise transmission through mask materials) and thin ‘wire form’ sources (to simultaneously characterise the spatial resolution and field of view of X-ray optics). A process of using virtual detectors to feed the input of virtual sources was used to shortcut the repeated computationally expensive modelling of a thermionic tube. With this efficient process and parallel computing, various combinations of pinhole and Coded Aperture optics could be efficiently tested and compared. To enable systematic comparisons the image quality metrics of signal, noise, contrast, resolution, field of view etc. are identified and procedures developed to extract them from images. ii For the experimental energy range of likely practical use, it was found that pure tungsten masks were superior to other alloys studied and that a 2mm pinhole gave the most generally suitable resolution/signal compromise. The results were consistent with physical experiment. A range of Coded Apertures were also modelled and compared favourably to experiment. The pinhole work on field of view informs the envelope within which coded apertures could avoid partial coding. The HEXITEC energy dispersive image plate was used to collect experimental images from a multi material quadrant. The image was simulated accurately using PAXI. Further, modelling with PAXI allowed the distinct interaction processes giving rise to image characteristics to be isolated. This concept was extended with a unique and innovative 2π hemispherical detector, which efficiently captured backscatter X-rays from carbon, copper, manganese dioxide, and lead when shielded and unshielded. This process allowed the brightness of materials to be studied, as governed by the complex combination of attenuation and cross section with angle. Further, the relative contributions from Compton, elastic and fluorescent processes to image brightness and spectral features could be isolated and compared with angle. This was conducted with/without shielding. This cannot be achieved by experiment, and pilots how modelling can inform the best beam energies and detector angles where the backscatter X-rays contain the right information to characterise materials and structures. This work includes significant use of simulation and also a strong supporting element of physical experimentation. The development of modelling techniques and their exploitation can give information that physical experiment cannot, whilst experimentation has been shown to validate the use of simulation and identify some limitationsItem Open Access Estimating and visualising imprecision in radiological emergency response assessments(2011-09-09) Haywood, S. M.; Healy, Matthew J. F.; Rogers, KeithAfter an accidental release of radioactivity to atmosphere, modelling assessments are needed to predict what the contamination levels are likely to be and what measures need to be taken to protect human health. These predictions will be imprecise due to lack of knowledge about the nature of the release and the weather, and also due to measurement inaccuracy. This thesis describes work to investigate this imprecision and to find better ways of including it in assessments and representing it in results. It starts by reviewing exposure pathways and the basic dose calculations in an emergency response assessment. The possible variability of key parameters in emergency dose calculations is considered, and ranges are developed for each. The imprecision typically associated with calculational endpoints is explored through a sensitivity study. This has been done using both a simple Gaussian atmospheric dispersion model and also real-time weather data in combination with a complex atmospheric dispersion model. The key parameters influencing assessment imprecision are identified. These are demonstrated to be factors relating to the release, arising from inevitable lack of knowledge in the early stages of an accident, and factors relating to meteorology and dispersion. An alternative improved approach to emergency response assessments is then outlined, which retains a simple and transparent assessment capability but which also indicates the imprecision associated with the results through incomplete knowledge. This tool uses input from real-time atmospheric dispersion and weather prediction tools. A prototype version of the tool has been created and this has been used to produce example results. The final stage of the thesis describes the use of the new tool to develop ways in which imprecise or uncertain information can be presented to decision makers. Alternative presentational techniques are demonstrated using example results.Item Open Access A fast and reliable approach to simulating the output from an x-ray tube used for developing security backscatter imaging(SPIE, 2017-08-10) Vella, Anna; Munoz, Andre Arelius Marcus; Healy, Matthew J. F.; Lane, David W.; Lockley, D.; Zhou, J. G.The PENELOPE Monte Carlo simulation code was used alongside the SpekCalc code to simulate X-ray energy spectra from a VJ Technologies’ X-ray generator at a range of anode voltages. The PENELOPE code is often utilised in medicine but is here applied to develop coded aperture and pinhole imaging systems for security purposes. The greater computational burden of PENELOPE over SpekCalc is warranted by its greater flexibility and output information. The model was designed using the PENGEOM sub-tool and consists of a tungsten anode and five layers of window materials. The photons generated by a mono-energetic electron beam are collected by a virtual detector placed after the last window layer, and this records the spatial, angular and energy distributions which are then used as the X-ray source for subsequent simulations. The process of storing X-ray outputs and using them as a virtual photon source can then be used efficiently for exploring a range of imaging conditions as the computationally expensive electron interactions in the anode need not be repeated. The modelled spectra were validated with experimentally determined spectra collected with an Amptek X-123 Cadmium Telluride detector placed in front of the source.Item Open Access A framework for the systematic realisation of phenomena for enhanced sensing of radiological and nuclear materials, and radiation(IOP, 2015-08-13) Healy, Matthew J. F.The quest for new sensing phenomena continues because detecting, discriminating, identifying, measuring and monitoring nuclear materials and their radiation from greater range, at lower concentrations, and in a more timely fashion brings greater safety, security and efficiency. The potential phenomena are diverse, and those that have been realised can be found in disparate fields of science, engineering and medicine, which makes the full range difficult to realise and record. The framework presented here offers a means to systematically and comprehensively explore nuclear sensing phenomena. The approach is based on the fundamental concepts of matter and energy, where the sequence starts with the original nuclear material and its emissions, and progressively considers signatures arising from secondary effects and the emissions from associated materials and the environment. Concepts of operations such as active and passive interrogation, and networked sensing are considered. In this operational light, unpacking nuclear signatures forces a fresh look at the sensing concept. It also exposes how some phenomena that exist in established technology may be considered novel based on how they could be exploited rather than what they fundamentally are. This article selects phenomena purely to illustrate the framework and how it can be best used to foster creativity in the quest for novel phenomena rather than exhaustively listing, categorising or comparing any practical aspects of candidate phenomena.Item Open Access Investigating electric field induced molecular distortions in polypropylene using Raman spectroscopy(Elsevier, 2020-09-13) Vetter, Marleen; Healy, Matthew J. F.; Lane, David W.Polymeric electric insulators are an integral part of many electronic circuits and systems. Changes induced by an electric field can affect various mechanisms; including electrical polarisation and electromechanical properties. Changes in the dielectric material can be tracked using spectroscopic methods. This study has shown that analysing polypropylene under electric field stress using Raman spectroscopy in combination with principal component analysis allows small changes in the non-crystalline phase to be identified. We have observed that for polypropylene, vibrational motion and changes in conformation occur mostly within the tie molecules connecting the overall cluster network. Amorphous molecular chains in the spherulites were also found to orient and form into a smectic mesophase. These electromechanical changes at the micro- and macromolecular level were found to be generally reversible once the stress is removed. However, with increased aging, these changes may lead to adverse structural changes and thus, in the future, this information may be used to inform faults and defect detection within polymeric dielectric materials.Item Open Access Low open fraction coded masks for x-ray backscatter imaging(SPIE, 2018-09-24) Munoz, Andre Arelius Marcus; Vella, Anna; Healy, Matthew J. F.; Lane, David W.; Jupp, Ian; Lockley, DavidPrevious research has indicated that coded masks with open fractions <0.5 are optimal for imaging some types of far-field scenes. The open fraction, in this case, refers to the ratio of open elements in the mask, with values <0.5 considered as low open fraction. Research is limited by the sparsity of <0.5 open fractions masks; thus a further 94 lower open fraction arrays are calculated and presented. These include the dilute uniformly redundant array and singer set, along with information on imaging potential, array sizes, and open fractions. Signal-to-noise ratio reveals the 0.5 open fraction modified uniformly redundant array to be the optimal coded mask for near-field x-ray backscatter imaging, over the lower open fraction singer set, dilute uniformly redundant and random arrayItem Open Access Potential contribution of selected metallic restorative dentistry materials to X-ray fluorescence(Cambridge University Press, 2019-06-17) Andrade, Edson R.; Oliveira, Ana Lucia N.; Funcke, Luisa N.; Souza, Leonardo Henrique F. F.; Healy, Matthew J. F.; Vital, Helio C.Recent advances have led to the use of new materials in dental restoration which is an area of rapid growth. Applications include improving oral aesthetics and essential rehabilitation, whilst procedures range from the recovery of partial elements (inlays) to fitting dental implants. Ceramics, polymers and metallic materials have all been successfully employed in dental applications and benefit from new cost efficient manufacturing techniques. The application of radiographic techniques in dentistry and other medicine is also increasing, and the combination of new materials and radiation can lead to an elevated health risk. X-rays can interact with metallic materials producing X-ray fluorescence, which can increase the radiation dose in proximity to restorative material and increase the risk of live biological tissue becoming cancerous. The issue demands consideration so that the biological risks associated with such procedures are kept as low as possible. Comparisons of doses calculated for several materials have provided evidence that the Ti cp and NiCrTi alloys present less contribution to the increase of dose in surrounding soft tissue and the potential deleterious biological effects. On the other hand, Amalgam appears to be the most deleterious alloy.Item Open Access Radiological risk assessment by convergence methodology model in RDD scenarios(Wiley, 2016-02-19) Rother, Fagner C.; Rebello, Wilson F.; Healy, Matthew J. F.; Silva, Mauricio M.; Cabral, Paulo A. M.; Vital, Helio C.; Andrade, Edson R.A radiological dispersal device (RDD) is a simple weapon capable of causing human harm, environmental contamination, disruption, area denial, and economic cost. It can affect small, large, or long areas depending on atmospheric stability. The risk of developing a radio-induced cancer depends on exposure, and an effective response depends upon available timely guidance. This article proposes and demonstrates a convergence of three different capabilities to assess risk and support rapid safe resource efficient response. The three capabilities that are integrated are Hotspot for dispersion, RERF for epidemiological risk, and RESRAD-RDD for response guidance. The combined methodology supports decisions on risk reduction and resource allocation through work schedules, the designation and composition of response teams, and siting for operations. In the illustrative RDD scenario, the contamination area for sheltering, evacuation, and long-term public concern was greatest for calm atmospheric conditions, whilst close-quarter responders faced highest dose rates for neutral atmospheric conditions. Generally, the risks to women responders were found to be significantly greater than for men, and the risks to 20-year-old responders were three times that of their 60-year-old counterparts for similar exposure.Item Open Access Rapid prototyping-coded masks for x-ray backscatter imaging(2018-08-22) Munoz, Andre Arelius Marcus; Vella, Anna; Healy, Matthew J. F.; Lane, David W.Coded masks (CM) often lack a self-supporting structure that is difficult to manufacture without recourse to drilled holes in place of ideal square apertures, degrading imaging properties. An alternative approach is presented with three-dimensional (3-D) printed CM molds cast with a radio-opaque material that allows square elements to be retained. Two methods are presented; hot casting a bismuth alloy (density 8.6 g cm − 3) and cold casting with tungsten powder/epoxy resin (densities 9.6 and 10.6 g cm − 3). A critical review of 3-D printed-CM fabrication along with some typical x-ray backscatter images is presented. A signal-to-noise ratio from both the machined tungsten and cold cast 3-D printed mask were comparable, with the former having a slight advantage. Also, 3-D printed cold cast masks were found to be more economical and easier to rapid prototype over traditional drilled tungsten masks.Item Open Access Search and location of body deposition sites: the role of winthropping and other innovative approaches(2019-02) Conway-Grim, Tanja; Healy, Matthew J. F.; Masters, PeterHomicide is regarded as one of the gravest of all crimes, and those cases where the body is initially missing are more difficult to solve, partly due to a potential loss of forensic evidence. This research investigated the potential role of winthropping (a counter-terrorism search technique developed by the British Army in Northern Ireland), tracking, wayfinding and lowland search and rescue techniques in the search for and location of rural body deposition sites. The focus was on ‘no body’ murders due to their high impact on society, and the people left behind having to deal with the ambiguous loss of their loved ones. Appropriate search training with the police, Lowland Rescue and military trackers was undertaken. Search professionals from within the police, military, lowland rescue and search organisations were interviewed. Specific distance data (known as track offset distance) of body deposition sites and locations where missing suicidal males were found, were compared to see whether their search parameters were similar. Training differences were noted especially relating to navigation and map reading. Most interviewees were familiar with winthropping, but few had applied its principles to the search and location of body deposition sites. ‘Fault lines’ surfaced as an (unexpected) topic, specifically: communication, financial constraints, statistics, rank and tasking. Homicide was seen as rare and complex, with accurate, intelligence-led tasking being a priority. The use of outside agencies (such as man-trackers and Lowland Rescue) seemed very much dependent upon the police search professional’s personal preference and experience, rather than a consistent national evidence-based approach.Item Open Access Simulated nuclear contamination scenario, solid cancer risk assessment, and support to decision(De Gruyter Open, 2019-04-01) Lima, Sergio X.; Costa, Karolina P. S.; Lima, Zelmo R.; Rother, Fagner C.; Araujo, Olga M. O.; Vital, Helio C.; Brum, Tercio; Wilson, F.R.S; Amorim, Jose Carlos C.; Healy, Matthew J. F.; Andrade, Edson R.The detonation of an (hypothetical) improvised nuclear device (IND) can generate atmospheric release of radioactive material in the form of particles and dust that ultimately contaminate the soil. In this study, the detonation of an IND in an urban area was simulated, and its effects on humans were determined. The risk of solid caner development due to radiation was calculated by taking into account prompt radiation and whole-body exposure of individuals near the detonation site up to 10 km. The excess relative risk (ERR) of developing solid cancer was evaluated by using the mathematical relationship from the Radiation Effects Research Foundation (RERF) studies and those from the HotSpot code. The methodology consists of using output data obtained from simulations performed with the HotSpot health physics code plugging in such numbers into a specific given equations used by RERF to evaluate the resulting impact. Such a preliminary procedure is expected to facilitate the decision-making process significantly.Item Open Access The use of simulation to optimize the pinhole diameter and mask thickness for an x-ray backscatter imaging system(SPIE, 2017-08-10) Vella, Anna; Munoz, Andre Arelius Marcus; Healy, Matthew J. F.; Lane, David W.; Lockley, D.The PENELOPE Monte Carlo simulation code was used to determine the optimum thickness and aperture diameter of a pinhole mask for X-ray backscatter imaging in a security application. The mask material needs to be thick enough to absorb most X-rays, and the pinhole must be wide enough for sufficient field of view whilst narrow enough for sufficient image spatial resolution. The model consisted of a fixed geometry test object, various masks with and without pinholes, and a 1040 x 1340 pixels’ area detector inside a lead lined camera housing. The photon energy distribution incident upon masks was flat up to selected energy limits. This artificial source was used to avoid the optimisation being specific to any particular X-ray source technology. The pixelated detector was modelled by digitising the surface area represented by the PENELOPE phase space file and integrating the energies of the photons impacting within each pixel; a MATLAB code was written for this. The image contrast, signal to background ratio, spatial resolution, and collimation effect were calculated at the simulated detector as a function of pinhole diameter and various thicknesses of mask made of tungsten, tungsten/epoxy composite or bismuth alloy. A process of elimination was applied to identify suitable masks for a viable X-ray backscattering security application.Item Open Access X-ray backscatter radiography with lower open fraction coded masks(SPIE, 2017-08-10) Munoz, Andre Arelius Marcus; Vella, Anna; Healy, Matthew J. F.; Lane, David W.; Jupp, Ian; Lockley, D.Single sided radiographic imaging would find great utility for medical, aerospace and security applications. While coded apertures can be used to form such an image from backscattered X-rays they suffer from near field limitations that introduce noise. Several theoretical studies have indicated that for an extended source the images signal to noise ratio may be optimised by using a low open fraction (<0.5) mask. However, few experimental results have been published for such low open fraction patterns and details of their formulation are often unavailable or are ambiguous. In this paper we address this process for two types of low open fraction mask, the dilute URA and the Singer set array. For the dilute URA the procedure for producing multiple 2D array patterns from given 1D binary sequences (Barker codes) is explained. Their point spread functions are calculated and their imaging properties are critically reviewed. These results are then compared to those from the Singer set and experimental exposures are presented for both type of pattern; their prospects for near field imaging are discussed.