Effect of CT electron density identification on Monte Carlo simulations of radiotherapeutic treatments

Introduction: The accurate identification of tissue electron densities is of great importance for Monte Carlo (MC) dose calculations. When converting patient CT data into a voxelised format suitable for MC simulations, however, it is common to simplify the assignment of electron densities so that the complex tissues existing in the human body are categorized into a few basic types. This study examines the effects that the assignment of tissue types and the calculation of densities can have on the results of MC simulations, for the particular case of a Siemen’s Sensation 4 CT scanner located in a radiotherapy centre where QA measurements are routinely made using 11 tissue types (plus air). Methods: DOSXYZnrc phantoms are generated from CT data, using the CTCREATE user code, with the relationship between Hounsfield units (HU) and density determined via linear interpolation between a series of specified points on the ‘CT-density ramp’ (see Figure 1(a)). Tissue types are assigned according to HU ranges. Each voxel in the DOSXYZnrc phantom therefore has an electron density (electrons/cm3) defined by the product of the mass density (from the HU conversion) and the intrinsic electron density (electrons /gram) (from the material assignment), in that voxel. In this study, we consider the problems of density conversion and material identification separately: the CT-density ramp is simplified by decreasing the number of points which define it from 12 down to 8, 3 and 2; and the material-type-assignment is varied by defining the materials which comprise our test phantom (a Supertech head) as two tissues and bone, two plastics and bone, water only and (as an extreme case) lead only. The effect of these parameters on radiological thickness maps derived from simulated portal images is investigated. Results & Discussion: Increasing the degree of simplification of the CT-density ramp results in an increasing effect on the resulting radiological thickness calculated for the Supertech head phantom. For instance, defining the CT-density ramp using 8 points, instead of 12, results in a maximum radiological thickness change of 0.2 cm, whereas defining the CT-density ramp using only 2 points results in a maximum radiological thickness change of 11.2 cm. Changing the definition of the materials comprising the phantom between water and plastic and tissue results in millimetre-scale changes to the resulting radiological thickness. When the entire phantom is defined as lead, this alteration changes the calculated radiological thickness by a maximum of 9.7 cm. Evidently, the simplification of the CT-density ramp has a greater effect on the resulting radiological thickness map than does the alteration of the assignment of tissue types. Conclusions: It is possible to alter the definitions of the tissue types comprising the phantom (or patient) without substantially altering the results of simulated portal images. However, these images are very sensitive to the accurate identification of the HU-density relationship. When converting data from a patient’s CT into a MC simulation phantom, therefore, all possible care should be taken to accurately reproduce the conversion between HU and mass density, for the specific CT scanner used. Acknowledgements: This work is funded by the NHMRC, through a project grant, and supported by the Queensland University of Technology (QUT) and the Royal Brisbane and Women's Hospital (RBWH), Brisbane, Australia. The authors are grateful to the staff of the RBWH, especially Darren Cassidy, for assistance in obtaining the phantom CT data used in this study. The authors also wish to thank Cathy Hargrave, of QUT, for assistance in formatting the CT data, using the Pinnacle TPS. Computational resources and services used in this work were provided by the HPC and Research Support Group, QUT, Brisbane, Australia.

Phantom Scatter and the A-SI EPID

Introduction: The use of amorphous-silicon electronic portal imaging devices (a-Si EPIDs) for dosimetry is complicated by the effects of scattered radiation. In photon radiotherapy, primary signal at the detector can be accompanied by photons scattered from linear accelerator components, detector materials, intervening air, treatment room surfaces (floor, walls, etc) and from the patient/phantom being irradiated. Consequently, EPID measurements which presume to take scatter into account are highly sensitive to the identification of these contributions. One example of this susceptibility is the process of calibrating an EPID for use as a gauge of (radiological) thickness, where specific allowance must be made for the effect of phantom-scatter on the intensity of radiation measured through different thicknesses of phantom. This is usually done via a theoretical calculation which assumes that phantom scatter is linearly related to thickness and field-size. We have, however, undertaken a more detailed study of the scattering effects of fields of different dimensions when applied to phantoms of various thicknesses in order to derive scattered-primary ratios (SPRs) directly from simulation results. This allows us to make a more-accurate calibration of the EPID, and to qualify the appositeness of the theoretical SPR calculations. Methods: This study uses a full MC model of the entire linac-phantom-detector system simulated using EGSnrc/BEAMnrc codes. The Elekta linac and EPID are modelled according to specifications from the manufacturer and the intervening phantoms are modelled as rectilinear blocks of water or plastic, with their densities set to a range of physically realistic and unrealistic values. Transmissions through these various phantoms are calculated using the dose detected in the model EPID and used in an evaluation of the field-size-dependence of SPR, in different media, applying a method suggested for experimental systems by Swindell and Evans [1]. These results are compared firstly with SPRs calculated using the theoretical, linear relationship between SPR and irradiated volume, and secondly with SPRs evaluated from our own experimental data. An alternate evaluation of the SPR in each simulated system is also made by modifying the BEAMnrc user code READPHSP, to identify and count those particles in a given plane of the system that have undergone a scattering event. In addition to these simulations, which are designed to closely replicate the experimental setup, we also used MC models to examine the effects of varying the setup in experimentally challenging ways (changing the size of the air gap between the phantom and the EPID, changing the longitudinal position of the EPID itself). Experimental measurements used in this study were made using an Elekta Precise linear accelerator, operating at 6MV, with an Elekta iView GT a-Si EPID. Results and Discussion: 1. Comparison with theory: With the Elekta iView EPID fixed at 160 cm from the photon source, the phantoms, when positioned isocentrically, are located 41 to 55 cm from the surface of the panel. At this geometry, a close but imperfect agreement (differing by up to 5%) can be identified between the results of the simulations and the theoretical calculations. However, this agreement can be totally disrupted by shifting the phantom out of the isocentric position. Evidently, the allowance made for source-phantom-detector geometry by the theoretical expression for SPR is inadequate to describe the effect that phantom proximity can have on measurements made using an (infamously low-energy sensitive) a-Si EPID. 2. Comparison with experiment: For various square field sizes and across the range of phantom thicknesses, there is good agreement between simulation data and experimental measurements of the transmissions and the derived values of the primary intensities. However, the values of SPR obtained through these simulations and measurements seem to be much more sensitive to slight differences between the simulated and real systems, leading to difficulties in producing a simulated system which adequately replicates the experimental data. (For instance, small changes to simulated phantom density make large differences to resulting SPR.) 3. Comparison with direct calculation: By developing a method for directly counting the number scattered particles reaching the detector after passing through the various isocentric phantom thicknesses, we show that the experimental method discussed above is providing a good measure of the actual degree of scattering produced by the phantom. This calculation also permits the analysis of the scattering sources/sinks within the linac and EPID, as well as the phantom and intervening air. Conclusions: This work challenges the assumption that scatter to and within an EPID can be accounted for using a simple, linear model. Simulations discussed here are intended to contribute to a fuller understanding of the contribution of scattered radiation to the EPID images that are used in dosimetry calculations. Acknowledgements: This work is funded by the NHMRC, through a project grant, and supported by the Queensland University of Technology (QUT) and the Royal Brisbane and Women's Hospital, Brisbane, Australia. The authors are also grateful to Elekta for the provision of manufacturing specifications which permitted the detailed simulation of their linear accelerators and amorphous-silicon electronic portal imaging devices. Computational resources and services used in this work were provided by the HPC and Research Support Group, QUT, Brisbane, Australia.

Learning opportunities : a partnership, connecting learning with projects

Major construction projects undertaken on university campuses are an ideal opportunity to connect learners in related disciplines to the real thing. How often do universities take that opportunity, make the connection and value add to projects being carried out? Discussion with students and academic staff will consistently generate enthusiasm for creating learning activities and resources related to projects. Some typical disciplines are project management, all fields of engineering, architecture, interior design and information technology. Some other areas that may not at first seem obvious are business, marketing, communication and public relations. The authors will provide a case study based on the new Queensland University of Technology (QUT) Science and Engineering Centre project of how the partnership between QUT and Leighton Contractors, the managing contractor, has delivered excellent learning opportunities through the design and construction phases of the Science and Engineering Centre project.

Communication choices to engage participation of rural Indonesian craftspeople in development projects

In participatory design projects, maintaining effective communication between facilitator and participant is essential. This paper describes the consideration given to the choice of communication modes to engage participation of rural Indonesian craftspeople over the course of a significant 3 year project that aims to grow their self-determination, design and business skill. We demonstrate the variety and subtlety of oral and written forms of communication used by the facilitator during the project. The culture, the communication skill and the influence of tacit knowledge affect the effectiveness of some modes of communication over the others, as well as the available infrastructure. Considerations are specific to the case of rural Indonesian craftspeople, but general lessons can be drawn.

Sharia-compliant financing in Indonesia infrastructure projects

As the adoption of project financing is gaining momentum, there is a concurrent need of innovation in project financing scheme in order to accelerate infrastructure assets provision in Indonesia. As the largest Muslim population in the world, sharia-compliant financing offers tremendous potential as a source for infrastructure financing for Indonesia. To realize this potential, there is a need of a framework to guide its adoption. Hence this paper discusses the potential implementation of Islamic finance to fund infrastructure projects in Indonesia. Through comparative analysis, this paper illustrates how Islamic principles can be incorporated into Indonesian infrastructure project financing.

YAWL4Industry : reflections on using YAWL for industry projects

The Yet Another Workflow Language (YAWL) language and environment has been used to prototype, verify, execute and analyse business processes in a wide variety of industrial domains, such as telephony, construction, supply chain, insurance services, medical environments, personnel management and the creative arts. These engagements offer the YAWL researcher community a great opportunity to validate our research findings within an industry setting, as well as discovery of possible enhancements from the end user perspective. This paper describes three such industry projects, discusses why YAWL was chosen and how it was used in each, and reacts on the insights gained along the way.

How much is that data in the window? Advertising your research data with QUT Library

Queensland University of Technology (QUT) Library offers a range of resources and services to researchers as part of their research support portfolio. This poster will present key features of two of the data management services offered by research support staff at QUT Library. The first service is QUT Research Data Finder (RDF), a product of the Australian National Data Service (ANDS) funded Metadata Stores project. RDF is a data registry (metadata repository) that aims to publicise datasets that are research outputs arising from completed QUT research projects. The second is a software and code registry, which is currently under development with the sole purpose of improving discovery of source code and software as QUT research outputs. RESEARCH DATA FINDER As an integrated metadata repository, Research Data Finder aligns with institutional sources of truth, such as QUT’s research administration system, ResearchMaster, as well as QUT’s Academic Profiles system to provide high quality data descriptions that increase awareness of, and access to, shareable research data. The repository and its workflows are designed to foster better data management practices, enhance opportunities for collaboration and research, promote cross-disciplinary research and maximise the impact of existing research data sets. SOFTWARE AND CODE REGISTRY The QUT Library software and code registry project stems from concerns amongst researchers with regards to development activities, storage, accessibility, discoverability and impact, sharing, copyright and IP ownership of software and code. As a result, the Library is developing a registry for code and software research outputs, which will use existing Research Data Finder architecture. The underpinning software for both registries is VIVO, open source software developed by Cornell University. The registry will use the Research Data Finder service instance of VIVO and will include a searchable interface, links to code/software locations and metadata feeds to Research Data Australia. Key benefits of the project include:improving the discoverability and reuse of QUT researchers’ code and software amongst QUT and the QUT research community; increasing the profile of QUT research outputs on a national level by providing a metadata feed to Research Data Australia, and; improving the metrics for access and reuse of code and software in the repository.

Improving the quality of fourth year civil engineering research projects through bibliographic instruction

Faculty and reference librarians at the Queensland University of Technology have collaborated in an attempt to improve the quality of literature reviews in civil engineering final -year research projects. This article describes the instructional program devised and the level of faculty support for the librarians' contribution, and presents survey results revealing how students could most benefit from BI and how the classroom collaboration affected student project work. The authors offer some observations about the possible impact of 81 in general, and on engineers in particular, which may provide a focus for future research.

Are we there yet? Early years reform in Queensland : stakeholder perspectives on the introduction of funded preschool programs in long day care services

Australian educators are currently engaging with wide-ranging, national early childhood reform that is reshaping early childhood education and care. The Australian reform agenda reflects many of the early childhood policy directions championed by bodies such as the Organisation for Economic Cooperation and Development and the United Nations Children's Education Fund, and is based on the dual discourse of (i) starting strong and (ii) investing in the early years. However, despite its traction in policy rhetoric and policy there is little empirical evidence of how reform is being played out. This paper reports on research undertaken in collaboration with the Queensland Office for Early Childhood Education and Care to generate sector feedback on one element of the reform agenda, the implementation of universal preschool in Queensland. The study aimed to determine the efficacy of the new policy in supporting the provision of 'approved preschool programs' within long day care services. Drawing together the views and experiences of a range of stakeholders, including peak organisations, service providers, directors, preschool teachers and government policy officers, it provides a situated case study of the implementation of universal preschool, and offers empirical evidence of how this policy is being played out at the local level. The paper identifies the opportunities and challenges in implementing universal preschool in Queensland that may have bearing on early childhood reform in Australia as well as other countries. Discussion of key findings is set within an overview of the ECEC policy agenda in Australia, with a particular focus on the commitment to universal preschool. Les éducateurs australiens s’engagent présentement dans une vaste réforme nationale de la petite enfance qui remodèle l'éducation et l’accueil de la petite enfance. Le programme de la réforme australienne reflète plusieurs des orientations en politique de la petite enfance soutenues par des organismes comme l'Organisation de coopération et de développement économiques (OCDE) et le Fonds des Nations Unies pour les enfants (UNICEF). Il s’appuie sur le double discours de (i) un bon départ et de (ii) l’investissement dans les premières années. Cependant, en dépit de son attrait en rhétorique de politique et en politique il y a peu de données empiriques sur la façon dont la réforme se déroule. Cet article rend compte de la recherche entreprise en collaboration avec le bureau de l'éducation et l’accueil à la petite enfance du Queensland afin d’obtenir une rétroaction du secteur sur un élément de la réforme, la mise sur pied du préscolaire universel dans le Queensland. L'étude visait à déterminer l'efficacité de la nouvelle politique pour soutenir la disposition «programmes préscolaires approuvés» dans les services de garde à temps plein. En regroupant les perspectives et les expériences d'une gamme d’intervenants, y compris d’importantes organisations, des prestataires de service, des directeurs, des enseignants du préscolaire et des fonctionnaires de politique gouvernementale, elle constitue une étude de cas localisée de l'exécution la mise sur pied du préscolaire universel, et fournit des données empiriques sur la façon dont cette politique se met en place au niveau local. L’article identifie les opportunités et les défis liés à l’implantation du préscolaire universel au Queensland, qui pourraient avoir une portée sur la réforme de petite enfance en Australie ainsi que dans d'autres pays. La discussion des principaux résultats est faite en lien avec un aperçu global de la politique d'éducation et d’accueil de la petite enfance en Australie, avec un accent particulier sur l'engagement envers le préscolaire universel. Los educadores australianos actualmente están involucrados en una amplia reforma de la educación temprana nacional que está revolucionando la educación preescolar y los servicios de cuidado. El programa de reforma Australiana refleja muchas de las direcciones políticas relacionadas con la infancia temprana incitadas por organismos como la Organización de Cooperación y Desarrollo Económicos y el Fondo Educacional Infantil de las Naciones Unidas, y se basa en el doble discurso de (i) empezando fuertemente e (ii) invertir en los primeros años. Sin embargo, a pesar de su política de tracción en retórica y política, hay pocos datos empíricos de cómo la reforma se está llevando a cabo. Este documento informa sobre las investigaciones llevadas a cabo en colaboración con la Oficina de Queensland de Educación tempana y cuidados, para generar comentarios del sector, sobre uno de los elementos de la agenda de reforma, la aplicación del preescolar universal en Queensland. El estudio tiene como objetivo determinar la eficacia de la nueva política para apoyar la prestación de "programas preescolares aprovados" dentro se los servicios de guardería y cuidado. Reuniendo los puntos de vista y las experiencias de una serie de interesados, entre ellos algunas organizaciones cumbre, proveedores de servicios, los directores, los maestros preescolares y oficiales de política y gobierno, se logra un estudio simulado de la implementación del preescolar universal, y ofrece evidencia empírica de cómo esta política se está llevando a cabo en el plano local. El documento identifica las oportunidades y desafíos en la implementación del preescolar universal en Queensland, que puede repercutir en la reforma de la indancia temprana en Australia, así como en otros países. La discusión de los resultados claves se encuentra en el interior de una visión de la agenda política de ECEC en Australia, con un enfoque particular en el compromiso con el preescolar universal.

Community college faculty's teaching social networks and their implications for librarians

Collaboration between faculty and librarians is an important topic of discussion and research among academic librarians. These partnerships between faculty and librarians are vital for enabling students to become lifelong learners through their information literacy education. This research developed an understanding of academic collaborators by analyzing a community college faculty's teaching social networks. A teaching social network, an original term generated in this study, is comprised of communications that influence faculty when they design and deliver their courses. The communication may be formal (e.g., through scholarly journals and professional development activities) and informal (e.g., through personal communication) through their network elements. Examples of the elements of a teaching social network may be department faculty, administration, librarians, professional development, and students. This research asked 'What is the nature of faculty's teaching social networks and what are the implications for librarians?' This study moves forward the existing research on collaboration, information literacy, and social network analysis. It provides both faculty and librarians with added insight into their existing and potential relationships. This research was undertaken using mixed methods. Social network analysis was the quantitative data collection methodology and the interview method was the qualitative technique. For the social network analysis data, a survey was sent to full-time faculty at Las Positas College, a community college, in California. The survey gathered the data and described the teaching social networks for faculty with respect to their teaching methods and content taught. Semi-structured interviews were conducted following the survey with a sub-set of survey respondents to understand why specific elements were included in their teaching social networks and to learn of ways for librarians to become an integral part of the teaching social networks. The majority of the faculty respondents were moderately influenced by the elements of their network except the majority of the potentials were weakly influenced by the elements in their network in their content taught. The elements with the most influence on both teaching methods and content taught were students, department faculty, professional development, and former graduate professors and coursework. The elements with the least influence on both aspects were public or academic librarians, and social media. The most popular roles for the elements were conversations about teaching, sharing ideas, tips for teaching, insights into teaching, suggestions for ways of teaching, and how to engage students. Librarians' weakly influenced faculty in their teaching methods and their content taught. The motivating factors for collaboration with librarians were that students learned how to research, students' research projects improved, faculty saved time by having librarians provide the instruction to students, and faculty built strong working relationships with librarians. The challenges of collaborating with librarians were inadequate teaching techniques used when librarians taught research orientations and lack of time. Ways librarians can be more integral in faculty's teaching social networks included: more workshops for faculty, more proactive interaction with faculty, and more one-on-one training sessions for faculty. Some of the recommendations for the librarians from this study were develop a strong rapport with faculty, librarians should build their services in information literacy from the point of view of the faculty instead of from the librarian perspective, use staff development funding to attend conferences and workshops to improve their teaching, develop more training sessions for faculty, increase marketing efforts of the librarian's instructional services, and seek grant opportunities to increase funding for the library. In addition, librarians and faculty should review the definitions of information literacy and move from a skills based interpretation to a learning process.

Contracting for infrastructure projects as credence goods

Large infrastructure projects are a major responsibility of urban and regional governments, who usually lack expertise to fully specify the demanded projects. Contractors, typically experts on such projects due to experience with similar projects elsewhere, advise of the needed design in their bids. Producing the right design is nevertheless costly. We model such infrastructure projects taking into account their credence goods feature and the costly design effort they require and examine the performance of commonly used contracting methods. We show that when building costs are homogeneous and public information, multi-stage competitive bidding involving shortlisting of two contractors and contingent compensation of both contractors on design efforts outperforms sequential search and the traditional Design-and-Build approach. If building costs are private information of the contractors and are revealed to them after design cost is sunk, sequential search may be superior to the other two methods.

The challenges of managing complexity in projects : an Australian perspective

Project Management (PM) as an academic field is relatively new in Australian universities. Moreover, the field is distributed across four main areas: business (management), built environment and construction, engineering and more recently ICT (information systems). At an institutional level, with notable exceptions, there is little engagement between researchers working in those individual areas. Consequently, an initiative was launched in 2009 to create a network of PM researchers to build a disciplinary base for PM in Australia. The initiative took the form of a bi-annual forum. The first forum established the constituency and spread of PM research in Australia (Sense et al., 2011). This special issue of IJPM arose out of the second forum, held in 2012, that explored the notion of an Australian perspective on PM. At the forum, researchers were invited to collaborate to explore issues, methodological approaches, and theoretical positions underpinning their research and to answer the question: is there a distinctly Australian research agenda which responds to the current challenges of large and complex projects in our region? From a research point of view, it was abundantly clear at the forum that many of the issues facing Australian researchers are shared around the world. However, what emerged from the forum as the Australian perspective was a set of themes and research issues that dominate the Australia research agenda.

Changing times, persistent paradigms : women and men at work in projects

The Australian economy is currently supported by a resources boom and work opportunities in traditionally male dominated fields of construction and engineering and information technology are at a premium. Yet despite more than 25 years of anti discrimination and equal employment opportunity legislation these industries still employ few women in operational or management roles. This paper investigates the issue of the low representation of women in project management and their different work and career experiences through interviews with male and female project managers.

Sustainability in post disaster road infrastructure recovery projects in Queensland, Australia

Between mid 2010 and early 2013, Queensland road related infrastructures were devastated by flood and cyclone related natural disasters. Responding to these recent events and in preparing for more regular and intense climate-change induced events in future, the Queensland Government is now reviewing how post-disaster road infrastructure recovery projects are planned and delivered. In particular, there is awareness that rebuilding such infrastructure need sustainable strategies across economic, environmental and social dimensions. A comprehensive sustainability assessment framework for pre and post disaster situations can minimize negative impact on our communities, economy and environment. This research is underway to develop a comprehensive sustainability element frame work for post disaster management in road infrastructures in Queensland, Australia. Analyzing the implications of disruption to transport network and associated services is an important part of preparing local and regional responses to the impacts of natural disasters. This research can contribute to strategic planning, management leading to safe, efficient and integrated transport system that supports sustainable economic, social and environmental outcomes in Queensland. Within this context, this paper provides an overview of the qualitative mixed-method research approach involving literature reviews and case studies to explore and evaluate a number of sustainability elements with a view to develop operational strategies for disaster recovery road projects.