Computer aided detection of natural reference markers in serial radiographs of growing bone

This thesis describes the theoretical and experimental development and testing of a computer-based image processing system for the detection of stable structural features in serial radiographs of growing bone. The study is divided into three parts. First, a simple theoretical model for the detection of stable structures in a radiographic sequence was developed together with a more detailed statistical model of the processes which hinder detection. Analysis of the models indicated that the processing procedures needed to perform the detection were those described by the so-called "matched filter equation". Secondly, the assumptions of the model were tested in a series of experiments using serial radiographs of 24 children with implanted tantalum markers, drawn from the files of the University of Washington, USA. Information gained from these experiments prompted changes to the detection method to allow the radiographic data to comply with these assumptions and provide robustness against image noise. The method was implemented as a semi-automatic image processing system on a Sun 3/160 computer. The system was tested in a further series of experiments using a second sample of radiographs of 28 children with implanted markers and with radiographs of dried human skulls. The results of these experiments indicated that the system could detect persistent structural features whose positions were consistent with the stable tantalum markers and that the system was robust against minor changes in projection between radiographs. Finally, the detection system was applied to the investigation of mandibular incisor eruption from intra-alveolar to pubertal eruption stages using serial lateral cephalometric radiographs of 11 children. This investigation revealed two new features of incisor eruption: first, the eruption paths deviated lingually at, or just prior to, alveolar emergence; and second, post-emergence eruption was characterised by a labio-lingual oscillation of the crowns of the incisors

The Enron/Andersen Collapse: Ongoing Implications for Executive M.B.A. Programs

[This article is based on David Springate’s presentation at the 2002 E.M.B.A. Council meeting in Keystone, Colorado, USA.] The premise of this article is that we can help develop leadership among the business men and women that are our executive students and, at the same time, serve society and the economy better if we move to modify Executive MBA programs given recent events. Given corporate and ethical lapses by some executives, our programs need some new emphasis, courses and exposures. Parts of our existing programs need tweaking. Further there is need for increased emphasis on judgment formation. I offer below some suggestions for doing this and, also, results of a quick look for changes recently instituted in Executive MBA programs

An investigation of growth rotations of jaws

This thesis describes an investigation into the origin and mechanism of growth rotations of the jaws. The materials comprised serial lateral, frontal and oblique cephalometric radiographs of 11 untreated children (5 males and 6 females) with tantalum markers in the mandible and both maxillae. The radiographs were recorded annually over an average period of 9.6 years (mean age at initial records 7.21 years) and were drawn from the archives of the Mathews Longitudinal Growth Study of the University of California, USA. The investigation comprised two separate but related studies: (i) an initial survey examining the correlations between growth rotations of the jaws and growth changes at sites throughout the face; and (ii) an in-depth investigation of the patterning of the sequences of annual increments of growth employing time-series analysis to detect intra-individual co-ordination of growth. The initial survey revealed a series of associations that matched those found in previous implant studies but some exceptions. The main study extended these results and indicated that the vertical growth displacements of the ramus and anterior maxilla combined to produce growth rotation of the mandible while the horizontal to vertical distribution of maxillary growth displacement produced growth rotation of the maxilla. Growth rotations of the jaws were found to be co-ordinated with: vertical growth displacement of the ramus (p=0.030) and anterior maxilla (p=0.009); horizontal growth displacement of the mandible (p<<0.001) and maxilla (p=0.015); horizontal migration of the maxillary molars (p=0.034); changes in angulation of the maxillary molars (p=0.009); and changes in the postural height of the tongue (p=0.048). The patterning of the co-ordination between rotational and translational growth displacements of the jaws and growth related changes in the dentition suggests a linkage to postural changes in the mandible and tongue. Based on these findings an explanatory model is proposed for the origin and control of growth rotations of the jaws

Withdrawing performance indicators: retrospective analysis of general practice performance under UK Quality and Outcomes Framework

Objectives To investigate the effect of withdrawing incentives on recorded quality of care, in the context of the UK Quality and Outcomes Framework pay for performance scheme. Design Retrospective longitudinal study. Setting Data for 644 general practices, from 2004/05 to 2011/12, extracted from the Clinical Practice Research Datalink. Participants All patients registered with any of the practices over the study period—13 772 992 in total. Intervention Removal of financial incentives for aspects of care for patients with asthma, coronary heart disease, diabetes, stroke, and psychosis. Main outcome measures Performance on eight clinical quality indicators withdrawn from a national incentive scheme: influenza immunisation (asthma) and lithium treatment monitoring (psychosis), removed in April 2006; blood pressure monitoring (coronary heart disease, diabetes, stroke), cholesterol concentration monitoring (coronary heart disease, diabetes), and blood glucose monitoring (diabetes), removed in April 2011. Multilevel mixed effects multiple linear regression models were used to quantify the effect of incentive withdrawal. Results Mean levels of performance were generally stable after the removal of the incentives, in both the short and long term. For the two indicators removed in April 2006, levels in 2011/12 were very close to 2005/06 levels, although a small but statistically significant drop was estimated for influenza immunisation. For five of the six indicators withdrawn from April 2011, no significant effect on performance was seen following removal and differences between predicted and observed scores were small. Performance on related outcome indicators retained in the scheme (such as blood pressure control) was generally unaffected. Conclusions Following the removal of incentives, levels of performance across a range of clinical activities generally remained stable. This indicates that health benefits from incentive schemes can potentially be increased by periodically replacing existing indicators with new indicators relating to alternative aspects of care. However, all aspects of care investigated remained indirectly or partly incentivised in other indicators, and further work is needed to assess the generalisability of the findings when incentives are fully withdrawn

rEHR: An R package for manipulating and analysing Electronic Health Record data

Research with structured Electronic Health Records (EHRs) is expanding as data becomes more accessible; analytic methods advance; and the scientific validity of such studies is increasingly accepted. However, data science methodology to enable the rapid searching/extraction, cleaning and analysis of these large, often complex, datasets is less well developed. In addition, commonly used software is inadequate, resulting in bottlenecks in research workflows and in obstacles to increased transparency and reproducibility of the research. Preparing a research-ready dataset from EHRs is a complex and time consuming task requiring substantial data science skills, even for simple designs. In addition, certain aspects of the workflow are computationally intensive, for example extraction of longitudinal data and matching controls to a large cohort, which may take days or even weeks to run using standard software. The rEHR package simplifies and accelerates the process of extracting ready-for-analysis datasets from EHR databases. It has a simple import function to a database backend that greatly accelerates data access times. A set of generic query functions allow users to extract data efficiently without needing detailed knowledge of SQL queries. Longitudinal data extractions can also be made in a single command, making use of parallel processing. The package also contains functions for cutting data by time-varying covariates, matching controls to cases, unit conversion and construction of clinical code lists. There are also functions to synthesise dummy EHR. The package has been tested with one for the largest primary care EHRs, the Clinical Practice Research Datalink (CPRD), but allows for a common interface to other EHRs. This simplified and accelerated work flow for EHR data extraction results in simpler, cleaner scripts that are more easily debugged, shared and reproduced

Modelling Conditions and Health Care Processes in Electronic Health Records : An Application to Severe Mental Illness with the Clinical Practice Research Datalink

BACKGROUND: The use of Electronic Health Records databases for medical research has become mainstream. In the UK, increasing use of Primary Care Databases is largely driven by almost complete computerisation and uniform standards within the National Health Service. Electronic Health Records research often begins with the development of a list of clinical codes with which to identify cases with a specific condition. We present a methodology and accompanying Stata and R commands (pcdsearch/Rpcdsearch) to help researchers in this task. We present severe mental illness as an example. METHODS: We used the Clinical Practice Research Datalink, a UK Primary Care Database in which clinical information is largely organised using Read codes, a hierarchical clinical coding system. Pcdsearch is used to identify potentially relevant clinical codes and/or product codes from word-stubs and code-stubs suggested by clinicians. The returned code-lists are reviewed and codes relevant to the condition of interest are selected. The final code-list is then used to identify patients. RESULTS: We identified 270 Read codes linked to SMI and used them to identify cases in the database. We observed that our approach identified cases that would have been missed with a simpler approach using SMI registers defined within the UK Quality and Outcomes Framework. CONCLUSION: We described a framework for researchers of Electronic Health Records databases, for identifying patients with a particular condition or matching certain clinical criteria. The method is invariant to coding system or database and can be used with SNOMED CT, ICD or other medical classification code-lists

A Simulation Model for Assessing Alternate Strategies for Beef Production with Land, Energy and Economic Constraints

A computer model has been developed to analyze alternate management strategies and energy and economic constraints. Daily production of beef animals and growing crops is simulated in response to prevailing conditions and system interactions using the GASP IV simulation language. Complete inventories of plant dry matter, animal status, production resources and economic net worth are maintained over the simulation period

Ultrafast band structure control of a two-dimensional heterostructure

The electronic structure of two-dimensional (2D) semiconductors can be signicantly altered by screening effects, either from free charge carriers in the material itself, or by environmental screening from the surrounding medium. The physical properties of 2D semiconductors placed in a heterostructure with other 2D materials are therefore governed by a complex interplay of both intra- and inter-layer interactions. Here, using time- and angle-resolved photoemission, we are able to isolate both the layer-resolved band structure and, more importantly, the transient band structure evolution of a model 2D heterostructure formed of a single layer of MoS 2 on graphene. Our results reveal a pronounced renormalization of the quasiparticle gap of the MoS 2 layer. Following optical excitation, the band gap is reduced by up to ∼400 meV on femtosecond timescales due to a persistence of strong electronic interactions despite the environmental screening by the n-doped graphene. This points to a large degree of tuneability of both the electronic structure and electron dynamics for 2D semiconductors embedded in a van der Waals-bonded heterostructure.PostprintPeer reviewe