Prospective Estimation of Radiation Dose and Image Quality for Optimized CT Performance

X-ray computed tomography (CT) is a non-invasive medical imaging technique that generates cross-sectional images by acquiring attenuation-based projection measurements at multiple angles. Since its first introduction in the 1970s, substantial technical improvements have led to the expanding use of CT in clinical examinations. CT has become an indispensable imaging modality for the diagnosis of a wide array of diseases in both pediatric and adult populations [1, 2]. Currently, approximately 272 million CT examinations are performed annually worldwide, with nearly 85 million of these in the United States alone [3]. Although this trend has decelerated in recent years, CT usage is still expected to increase mainly due to advanced technologies such as multi-energy [4], photon counting [5], and cone-beam CT [6].

Despite the significant clinical benefits, concerns have been raised regarding the population-based radiation dose associated with CT examinations [7]. From 1980 to 2006, the effective dose from medical diagnostic procedures rose six-fold, with CT contributing to almost half of the total dose from medical exposure [8]. For each patient, the risk associated with a single CT examination is likely to be minimal. However, the relatively large population-based radiation level has led to enormous efforts among the community to manage and optimize the CT dose.

As promoted by the international campaigns Image Gently and Image Wisely, exposure to CT radiation should be appropriate and safe [9, 10]. It is thus a responsibility to optimize the amount of radiation dose for CT examinations. The key for dose optimization is to determine the minimum amount of radiation dose that achieves the targeted image quality [11]. Based on such principle, dose optimization would significantly benefit from effective metrics to characterize radiation dose and image quality for a CT exam. Moreover, if accurate predictions of the radiation dose and image quality were possible before the initiation of the exam, it would be feasible to personalize it by adjusting the scanning parameters to achieve a desired level of image quality. The purpose of this thesis is to design and validate models to quantify patient-specific radiation dose prospectively and task-based image quality. The dual aim of the study is to implement the theoretical models into clinical practice by developing an organ-based dose monitoring system and an image-based noise addition software for protocol optimization.

More specifically, Chapter 3 aims to develop an organ dose-prediction method for CT examinations of the body under constant tube current condition. The study effectively modeled the anatomical diversity and complexity using a large number of patient models with representative age, size, and gender distribution. The dependence of organ dose coefficients on patient size and scanner models was further evaluated. Distinct from prior work, these studies use the largest number of patient models to date with representative age, weight percentile, and body mass index (BMI) range.

With effective quantification of organ dose under constant tube current condition, Chapter 4 aims to extend the organ dose prediction system to tube current modulated (TCM) CT examinations. The prediction, applied to chest and abdominopelvic exams, was achieved by combining a convolution-based estimation technique that quantifies the radiation field, a TCM scheme that emulates modulation profiles from major CT vendors, and a library of computational phantoms with representative sizes, ages, and genders. The prospective quantification model is validated by comparing the predicted organ dose with the dose estimated based on Monte Carlo simulations with TCM function explicitly modeled.

Chapter 5 aims to implement the organ dose-estimation framework in clinical practice to develop an organ dose-monitoring program based on a commercial software (Dose Watch, GE Healthcare, Waukesha, WI). In the first phase of the study we focused on body CT examinations, and so the patient’s major body landmark information was extracted from the patient scout image in order to match clinical patients against a computational phantom in the library. The organ dose coefficients were estimated based on CT protocol and patient size as reported in Chapter 3. The exam CTDIvol, DLP, and TCM profiles were extracted and used to quantify the radiation field using the convolution technique proposed in Chapter 4.

With effective methods to predict and monitor organ dose, Chapters 6 aims to develop and validate improved measurement techniques for image quality assessment. Chapter 6 outlines the method that was developed to assess and predict quantum noise in clinical body CT images. Compared with previous phantom-based studies, this study accurately assessed the quantum noise in clinical images and further validated the correspondence between phantom-based measurements and the expected clinical image quality as a function of patient size and scanner attributes.

Chapter 7 aims to develop a practical strategy to generate hybrid CT images and assess the impact of dose reduction on diagnostic confidence for the diagnosis of acute pancreatitis. The general strategy is (1) to simulate synthetic CT images at multiple reduced-dose levels from clinical datasets using an image-based noise addition technique; (2) to develop quantitative and observer-based methods to validate the realism of simulated low-dose images; (3) to perform multi-reader observer studies on the low-dose image series to assess the impact of dose reduction on the diagnostic confidence for multiple diagnostic tasks; and (4) to determine the dose operating point for clinical CT examinations based on the minimum diagnostic performance to achieve protocol optimization.

Chapter 8 concludes the thesis with a summary of accomplished work and a discussion about future research.

Symptom burden and its relationship to functional performance in patients with chronic obstructive pulmonary disease

The aim of this study was to explore symptom burden and its relationship to functional performance in patients with COPD. A descriptive, cross-sectional, correlational survey design was used and a sample of 214 patients with COPD. The sample was recruited from patients attending one of the major teaching hospitals in Dublin. Symptom burden was measured using the Memorial Symptom Assessment Scale (MSAS), and the functional performance was measured using the Functional Performance Inventory-Short Form (FPISF). Findings revealed that participants experienced a median of 13 symptoms. The most burdensome symptoms were shortness of breath, lack of energy, difficulty sleeping, worrying, dry mouth, feeling nervous, feeling irritable, and feeling sad. Participants with very severe COPD had the greatest symptom burden, followed by those with severe COPD, moderate COPD, and mild COPD. Symptom burden was higher for the psychological symptoms compared to the physical symptoms. Participants with mild COPD had the highest functional performance, followed by those with moderate COPD, very severe COPD, and severe COPD. Twenty symptoms were negatively correlated with overall functional performance, indicating that high symptom burden for those symptoms was associated with low overall functional performance. Moderate, negative, statistically significant correlations were found between the total symptom burden and overall functional performance, physical symptom burden and overall functional performance and psychological symptom burden and overall functional performance. A negative linear relationship was found between total symptom burden and overall functional performance among all stages of COPD except the mild group. No relationship was found between total symptom burden and overall functional performance for the moderate group. Healthcare professionals need to broaden the clinical and research assessment of physical and psychological symptoms in COPD; alleviating the burden of these symptoms may promote improved functional performance.

The Validity of Broad and Narrow Personality Traits For Predicting Job Performance: The Differential Effects of Time

Research into the dynamicity of job performance criteria has found evidence suggesting the presence of rank-order changes to job performance scores across time as well as intraindividual trajectories in job performance scores across time. These findings have influenced a large body of research into (a) the dynamicity of validities of individual differences predictors of job performance and (b) the relationship between individual differences predictors of job performance and intraindividual trajectories of job performance. In the present dissertation, I addressed these issues within the context of the Five Factor Model of personality. The Five Factor Model is arranged hierarchically, with five broad higher-order factors subsuming a number of more narrowly tailored personality facets. Research has debated the relative merits of broad versus narrow traits for predicting job performance, but the entire body of research has addressed the issue from a static perspective -- by examining the relative magnitude of validities of global factors versus their facets. While research along these lines has been enlightening, theoretical perspectives suggest that the validities of global factors versus their facets may differ in their stability across time. Thus, research is needed to not only compare the relative magnitude of validities of global factors versus their facets at a single point in time, but also to compare the relative stability of validities of global factors versus their facets across time. Also necessary to advance cumulative knowledge concerning intraindividual performance trajectories is research into broad vs. narrow traits for predicting such trajectories. In the present dissertation, I addressed these issues using a four-year longitudinal design. The results indicated that the validities of global conscientiousness were stable across time, while the validities of conscientiousness facets were more likely to fluctuate. However, the validities of emotional stability and extraversion facets were no more likely to fluctuate across time than those of the factors. Finally, while some personality factors and facets predicted performance intercepts (i.e., performance at the first measurement occasion), my results failed to indicate a significant effect of any personality variable on performance growth. Implications for research and practice are discussed.

The Effects of Advanced Practice Nurses (APNs) as Intensivists in a Surgical Intensive Care Unit (SICU) on Patient Outcomes, Healthcare Charges, and APN Intensivist Services in the SICU

Intensive Care Units (ICUs) account for over 10 percent of all US hospital beds, have over 4.4 million patient admissions yearly, approximately 360,000 deaths, and account for close to 30% of acute care hospital costs. The need for critical care services has increased due to an aging population and medical advances that extend life. The result is efforts to improve patient outcomes, optimize financial performance, and implement models of ICU care that enhance quality of care and reduce health care costs. This retrospective chart review study examined the dose effect of APN Intensivists in a surgical intensive care unit (SICU) on differences in patient outcomes, healthcare charges, SICU length of stay, charges for APN intensivist services, and frequency of APNs special initiatives when the SICU was staffed by differing levels of APN Intensivist staffing over four time periods (T1-T4) between 2009 and 2011. The sample consisted of 816 randomly selected (204 per T1-T4) patient chart data. Study findings indicated reported ventilator associated pneumonia (VAP) rates, ventilator days, catheter days and catheter associated urinary tract infection (CAUTI) rates increased at T4 (when there was the lowest number of APN Intensivists), and there was increased pressure ulcer incidence in first two quarters of T4. There was no statistically significant difference in post-surgical glycemic control (M = 142.84, SD= 40.00), t (223) = 1.40, p = .17, and no statistically significant difference in the SICU length of stay among the time-periods (M= 3.27, SD = 3.32), t (202) = 1.02, p= .31. Charges for APN services increased over the 4 time periods from $11,268 at T1 to $51,727 at T4 when a system to capture APN billing was put into place. The number of new APN initiatives declined in T4 as the number of APN Intensivists declined. Study results suggest a dose effect of APN Intensivists on important patient health outcomes and on the number of APNs initiatives to prevent health complications in the SICU.

ISSP Position Stand: To Sample or to Specialize? Seven Postulates About Youth Sport Activities that Lead to Continued Participation and Elite Performance

A comprehensive approach to sport expertise should consider the entire situation that is comprised of the person, the task, the environment, and the complex interplay of these components (Hackfort, 1986). Accordingly, the Developmental Model of Sport Participation (Côté, Baker, & Abernethy, 2007; Côté & Fraser-Thomas, 2007) provides a comprehensive framework for sport expertise that outlines different pathways of involvement in sport. In pathways one and two, early sampling serves as the foundation for both elite and recreational sport participation. Early sampling is based on two main elements of childhood sport participation: 1) involvement in various sports and 2) participation in deliberate play. In contrast, pathway three shows the course to elite performance through early specialization in one sport. Early specialization implies a focused involvement on one sport and a large number of deliberate practice activities with the goal of improving sport skills and performance during childhood. This paper proposes seven postulates regarding the role that sampling and deliberate play, as opposed to specialization and deliberate practice, can have during childhood in promoting continued participation and elite performance in sport.

IMPROVING THE PERFORMANCE OF DATABASE-CENTRIC APPLICATIONS THROUGH PROGRAM ANALYSIS

Modern software applications are becoming more dependent on database management systems (DBMSs). DBMSs are usually used as black boxes by software developers. For example, Object-Relational Mapping (ORM) is one of the most popular database abstraction approaches that developers use nowadays. Using ORM, objects in Object-Oriented languages are mapped to records in the database, and object manipulations are automatically translated to SQL queries. As a result of such conceptual abstraction, developers do not need deep knowledge of databases; however, all too often this abstraction leads to inefficient and incorrect database access code. Thus, this thesis proposes a series of approaches to improve the performance of database-centric software applications that are implemented using ORM. Our approaches focus on troubleshooting and detecting inefficient (i.e., performance problems) database accesses in the source code, and we rank the detected problems based on their severity. We first conduct an empirical study on the maintenance of ORM code in both open source and industrial applications. We find that ORM performance-related configurations are rarely tuned in practice, and there is a need for tools that can help improve/tune the performance of ORM-based applications. Thus, we propose approaches along two dimensions to help developers improve the performance of ORM-based applications: 1) helping developers write more performant ORM code; and 2) helping developers configure ORM configurations. To provide tooling support to developers, we first propose static analysis approaches to detect performance anti-patterns in the source code. We automatically rank the detected anti-pattern instances according to their performance impacts. Our study finds that by resolving the detected anti-patterns, the application performance can be improved by 34% on average. We then discuss our experience and lessons learned when integrating our anti-pattern detection tool into industrial practice. We hope our experience can help improve the industrial adoption of future research tools. However, as static analysis approaches are prone to false positives and lack runtime information, we also propose dynamic analysis approaches to further help developers improve the performance of their database access code. We propose automated approaches to detect redundant data access anti-patterns in the database access code, and our study finds that resolving such redundant data access anti-patterns can improve application performance by an average of 17%. Finally, we propose an automated approach to tune performance-related ORM configurations using both static and dynamic analysis. Our study shows that our approach can help improve application throughput by 27--138%. Through our case studies on real-world applications, we show that all of our proposed approaches can provide valuable support to developers and help improve application performance significantly.

Developing an engineering approach for migrating from prescriptive to performance-based specification for concrete

The integral variability of raw materials, lack of awareness and appreciation of the technologies for achieving quality control and lack of appreciation of the micro and macro environmental conditions that the structures will be subjected, makes modern day concreting a challenge. This also makes Designers and Engineers adhere more closely to prescriptive standards developed for relatively less aggressive environments. The data from exposure sites and real structures prove, categorically, that the prescriptive specifications are inadequate for chloride environments. In light of this shortcoming, a more pragmatic approach would be to adopt performance-based specifications which are familiar to industry in the form of specification for mechanical strength. A recently completed RILEM technical committee made significant advances in making such an approach feasible.
Furthering a performance-based specification requires establishment of reliable laboratory and on-site test methods, as well as easy to perform service-life models. This article highlights both laboratory and on-site test methods for chloride diffusivity/electrical resistivity and the relationship between these tests for a range of concretes. Further, a performance-based approach using an on-site diffusivity test is outlined that can provide an easier to apply/adopt practice for Engineers and asset managers for specifying/testing concrete structures.

Influence of Forecasting, Planning and Controlling on the performance of Small and Medium Enterprises

Production Planning and Control (PPC) systems have grown and changed because of the developments in planning tools and models as well as the use of computers and information systems in this area. Though so much is available in research journals, practice of PPC is lagging behind and does not use much from published research. The practices of PPC in SMEs lag behind because of many reasons, which need to be explored. This research work deals with the effect of identified variables such as forecasting, planning and control methods adopted, demographics of the key person, standardization practices followed, effect of training, learning and IT usage on firm performance. A model and framework has been developed based on literature. Empirical testing of the model has been done after collecting data using a questionnaire schedule administered among the selected respondents from Small and Medium Enterprises (SMEs) in India. Final data included 382 responses. Hypotheses linking SME performance with the use of forecasting, planning and controlling were formed and tested. Exploratory factor analysis was used for data reduction and for identifying the factor structure. High and low performing firms were classified using a Logistic Regression model. A confirmatory factor analysis was used to study the structural relationship between firm performance and dependent variables.

Wearing Eye Tracking Technology During Batting Practice: Assessing the Experiences of Professional Baseball Athletes

Utilizing wearable technology in sport allows for the collection of motor behavior data during task engagement. This data can be assessed in real-time or retrospectively. Although enriching the scope of performance data, the consequences of wearable technology on the athlete-user, specifically the cognitive effects, has not been fully investigated, hence the purpose of this study. This qualitative study examines the cognitions of 57 professional baseball players who wore eye tracking technology whilst engaged in batting practice. Their verbal self-reports were framed by temporal context: before-during-after task. Three themes emerged during the pre-task segment: social appearance anxiety, claimed self-handicapping, and curiosity. During the task of batting, verbal behavior contained motivational and instructional overt self-talk while claimed self-handicapping was sustained. The final, post-performance segment was marked by the re-emergence of curiosity from the pre-task period as well as self-evaluation/appraisal. Given the participants were professional athletes, their performance has greater career implications than amateur competitors. Nonetheless, the verbal behavior elicited while wearing eye tracking technology indicates an awareness of the equipment by the user. This study found cognitive effects from wearable technology; more research is required to under-stand the scope and nature of those effects on cognitive and motor behaviors.

Blurred Lines: Performance Enhancement, Common Mental Disorders and Referral in the U.K. Athletic Population

Through the awareness-raising efforts of several high-profile current and former athletes, the issue of common mental disorders (CMD) in this population is gaining increasing attention from researchers and practitioners alike. Yet the prevalence is unclear and most likely, under-reported. Whilst the characteristics of the sporting environment may generate CMD within the athletic population, it also may exacerbate pre-existing conditions, and hence it is not surprising that sport psychology and sport science practitioners are anecdotally reporting increased incidences of athletes seeking support for CMDs. In a population where there are many barriers to reporting and seeking help for CMD, due in part to the culture of the high performance sporting environment, anecdotal reports suggest that those athletes asking for help are approaching personnel who they are most comfortable talking to. In some cases, this may be a sport scientist, the sport psychologist or sport psychology consultant. Among personnel in the sporting domain, there is a perception that the sport psychologist or sport psychology consultant is best placed to assist athletes seeking assistance for CMD. However, sport psychology as a profession is split by two competing philosophical perspectives; one of which suggests that sport psychologists should work exclusively with athletes on performance enhancement, and the other views the athlete more holistically and accepts that their welfare may directly impact on their performance. To add further complication, the development of the profession of sport psychology varies widely between countries, meaning that practice in this field is not always clearly defined. This article examines case studies that illustrate the blurred lines in applied sport psychology practice, highlighting challenges with the process of referral in the U.K. athletic population. The article concludes with suggestions for ensuring the field of applied sport psychology is continually evolving and reconfiguring to ensure that it continues to meet the demands of its clients.

Professional Practice in Learning and Development: How to Design and Deliver Plans for the Workplace

Introduction The world is changing! It is volatile, uncertain, complex and ambiguous. As cliché as it may sound the evidence of such dynamism in the external environment is growing. Business-as-usual is more of the exception than the norm. Organizational change is the rule; be it to accommodate and adapt to change, or instigate and lead change. A constantly changing environment is a situation that all organizations have to live with. What makes some organizations however, able to thrive better than others? Many scholars and practitioners believe that this is due to the ability to learn. Therefore, this book on developing Learning and Development (L&D) professionals is timely as it explores and discusses trends and practices that impact organizations, the workforce and L&D professionals. Being able to learn and develop effectively is the cornerstone of motivation as it helps to address people’s need to be competent and to be autonomous (Deci & Ryan, 2002; Loon & Casimir, 2008; Ryan & Deci, 2000). L&D stimulates and empowers people to perform. Organizations that are better at learning at all levels; the individual, group and organizational level, will always have a better chance of surviving and performing. Given the new reality of a dynamic external environment and constant change, L&D professionals now play an even more important role in their organizations than ever before. However, L&D professionals themselves are not immune to the turbulent changes as their practices are also impacted. Therefore, the challenges that L&D professionals face are two-pronged. Firstly, in relation to helping and supporting their organization and its workforce in adapting to the change, whilst, secondly developing themselves effectively and efficiently so that they are able to be one-step ahead of the workforce that they are meant to help develop. These challenges are recognised by the CIPD, as they recently launched their new L&D qualification that has served as an inspiration for this book. L&D plays a crucial role at both strategic (e.g. organizational capability) and operational (e.g. delivery of training) levels. L&D professionals have moved from being reactive (e.g. following up action after performance appraisals) to being more proactive (e.g. shaping capability). L&D is increasingly viewed as a driver for organizational performance. The CIPD (2014) suggest that L&D is increasingly expected to not only take more responsibility but also accountability for building both individual and organizational knowledge and capability, and to nurture an organizational culture that prizes learning and development. This book is for L&D professionals. Nonetheless, it is also suited for those studying Human Resource Development HRD at intermediate level. The term ‘Human Resource Development’ (HRD) is more common in academia, and is largely synonymous with L&D (Stewart & Sambrook, 2012) Stewart (1998) defined HRD as ‘the practice of HRD is constituted by the deliberate, purposive and active interventions in the natural learning process. Such interventions can take many forms, most capable of categorising as education or training or development’ (p. 9). In fact, many parts of this book (e.g. Chapters 5 and 7) are appropriate for anyone who is involved in training and development. This may include a variety of individuals within the L&D community, such as line managers, professional trainers, training solutions vendors, instructional designers, external consultants and mentors (Mayo, 2004). The CIPD (2014) goes further as they argue that the role of L&D is broad and plays a significant role in Organizational Development (OD) and Talent Management (TM), as well as in Human Resource Management (HRM) in general. OD, TM, HRM and L&D are symbiotic in enabling the ‘people management function’ to provide organizations with the capabilities that they need.

The impact of mindfulness on the wellbeing and performance of educators: A systematic review of the empirical literature

Given the potentially demanding nature of teaching, efforts are underway to develop practices that can improve the wellbeing of educators, including interventions based on mindfulness meditation. We performed systematic review of empirical studies featuring analyses of mindfulness in teaching contexts. Databases were reviewed from the start of records to January 2016. Eligibility criteria included empirical analyses of mindfulness and wellbeing outcomes acquired in relation to practice. A total of 19 papers met the eligibility criteria and were included in the systematic review, consisting of a total 1,981 participants. Studies were principally examined for outcomes such as burnout, anxiety, depression and stress, as well as more positive wellbeing measures (e.g., life satisfaction). The systematic review revealed that mindfulness was generally associated with positive outcomes in relation to most measures. However, the quality of the studies was inconsistent, and so further research is needed, particularly involving high-quality randomised control trials.

Self-regulatory behaviours and flow dispositions in musical practice: a survey with advanced performers

Flow experience, a holistic sensation of total involvement in an activity, seems to have positive influences on musical performance activities. Although its main requirements (balance between challenges and skills, clear goals and unequivocal feedback) are inherent elements of musical practice, there is a lack of research about flow occurrences in the context of musical practice and on how specific practice behaviours affect the experience of flow and its particular dimensions. The aims of this thesis were to investigate advanced performersʼ dispositions to flow in musical practice, and to investigate whether the frequency of these experiences of holistic engagement with practice are associated with self-regulatory practice behaviours. 168 advanced classicallytrained performers (male = 50.0%; female = 50.0%), ranging in age from 18 to 74 years (m = 34.41, SD = 12.39), answered a survey that included two measures: the Dispositional Short Flow Scale, assessing performersʼ flow dispositions, and the Self-Regulated Practice Behaviours Questionnaire, developed specifically for the present research. The overall results of the survey suggested that advanced musicians have high dispositions to flow in musical practice, but not associated with the participantsʼ demographic characteristics. Three of the individual flow indicators were less experienced, suggesting that the most intense flow experiences are rare in musical practice. However, the results point to the existence of another relevant experience, named optimal practice experience. Practice engagement levels were positively associated with knowledge of oneʼs own personal resources and a capacity for practice organization, but not with inclusion/use of external resources. A capacity for setting optimal practice goals was related to self-regulation and to immersion aspects of flow. Current findings offer new clues about the assessment of flow dispositions in performers, helping to clarify how daily practice can heighten positive affective responses in musicians who are vulnerable to the requirements and difficulties of deliberate practice, as well as to other negative practice outcomes. The current research questions issues pertaining to the optimization and sustaining of flow in daily practice, suggesting future directions in the study of the affective subjective functioning of engagement with deliberate practice.

Creative communities: shaping process through performance and play

This paper studies the use of play as a method to unlock creativity and innovation within a community of practice (a group of individuals who share a common interest and who see value in interaction to enhance their understanding). An analysis of communities of practice and the value of play informs evaluation of two case studies exploring the development of communities of practice, one within the discipline of videogames and one which bridges performing arts and videogames. The case studies provide qualitative data from which the potential of play as a method to inspire creativity and support the development of a potential community of practice is recognised. Establishing trust, disruption of process through play and reflection are key steps proposed in a ‘context provider’s framework’ for individuals or organisations to utilise in the design of activities to support creative process and innovation within a potential community of practice.

Performance of protective factors assessment in risk prediction for adults: systematic review and meta-analysis

Protective factors are neglected in risk assessment in adult psychiatric and criminal justice populations. This review investigated the predictive efficacy of selected tools that assess protective factors. Five databases were searched using comprehensive terms for records up to June 2014, resulting in 17 studies (n = 2,198). Results were combined in a multilevel meta-analysis using the R (R Core Team, R: A Language and Environment for Statistical Computing, Vienna, Austria: R Foundation for Statistical Computing, 2015) metafor package (Viechtbauer, Journal of Statistical Software, 2010, 36, 1). Prediction of outcomes was poor relative to a reference category of violent offending, with the exception of prediction of discharge from secure units. There were no significant differences between the predictive efficacy of risk scales, protective scales, and summary judgments. Protective factor assessment may be clinically useful, but more development is required. Claims that use of these tools is therapeutically beneficial require testing.