Novelty, distillation, and federation in machine learning for medical imaging

The practical application of deep learning methods in the medical domain has many challenges. Pathologies are diverse and very few examples may be available for rare cases. Where data is collected it may lie in multiple institutions and cannot be pooled for practical and ethical reasons. Deep learning is powerful for image segmentation problems but ultimately its output must be interpretable at the patient level. Although clearly not an exhaustive list, these are the three problems tackled in this thesis. To address the rarity of pathology I investigate novelty detection algorithms to find outliers from normal anatomy. The problem is structured as first finding a low-dimension embedding and then detecting outliers in that embedding space. I evaluate for speed and accuracy several unsupervised embedding and outlier detection methods. Data consist of Magnetic Resonance Imaging (MRI) for interstitial lung disease for which healthy and pathological patches are available; only the healthy patches are used in model training. I then explore the clinical interpretability of a model output. I take related work by the Canon team — a model providing voxel-level detection of acute ischemic stroke signs — and deliver the Alberta Stroke Programme Early CT Score (ASPECTS, a measure of stroke severity). The data are acute head computed tomography volumes of suspected stroke patients. I convert from the voxel level to the brain region level and then to the patient level through a series of rules. Due to the real world clinical complexity of the problem, there are at each level — voxel, region and patient — multiple sources of “truth”; I evaluate my results appropriately against these truths. Finally, federated learning is used to train a model on data that are divided between multiple institutions. I introduce a novel evolution of this algorithm — dubbed “soft federated learning” — that avoids the central coordinating authority, and takes into account domain shift (covariate shift) and dataset size. I first demonstrate the key properties of these two algorithms on a series of MNIST (handwritten digits) toy problems. Then I apply the methods to the BraTS medical dataset, which contains MRI brain glioma scans from multiple institutions, to compare these algorithms in a realistic setting

Unpacking pathways to diversified livelihoods from projects in Pacific Island coastal fisheries

Livelihood diversification has become an integral focus of policies and investments aiming to reduce poverty, vulnerability, and pressure on fishery resources in coastal communities around the globe. In this regard, coastal fisheries in the Pacific Islands have long been a sector where livelihood diversification has featured prominently. Yet, despite the widespread promotion and international investment in this strategy, the ability of externally funded livelihood diversification projects to facilitate improved resource management and rural development outcomes often remains inconsistent. We argue these inconsistencies can be attributed to a conceptual ambiguity stemming from a lack of attention and awareness to the complexity of livelihood diversification. There is still much to learn about the process of livelihood diversification, both in its theoretical conceptualizations and its practical applications. Herein, we utilize a common diversity framework to clarify some of this ambiguity by distinguishing three diversification pathways. These pathways are illustrated using an ideal–typical Pacific Island coastal household and supported by examples provided in the literature that detail livelihood diversification projects in the Pacific. Through this perspective, we seek a more nuanced understanding of what is meant within the policy and practice goal of livelihood diversification. Thereby enabling more targeted and deliberate planning for development investments that facilitates outcomes in support of sustainable livelihoods

Considerations in Building and Fielding MPDV

Author Institution: National Security Technologies, LLCSlides presented at the 6th Annual Photonic Doppler Velocimetry (PDV) Workshop held at Lawrence Livermore National Laboratory, Livermore, California, November 3-4, 2011

Effectiveness of offering tailored text message, self-help smoking cessation support to pregnant women who want information on stopping smoking: MiQuit3 randomised controlled trial and meta-analysis.

AIMS: To test the efficacy of 'MiQuit', a tailored, self-help, text message stop smoking programme for pregnancy, as an adjunct to usual care (UC) for smoking cessation in pregnancy. DESIGN: Multicentre, open, two-arm, parallel-group, superiority randomised controlled trial (RCT) and a trial sequential analysis (TSA) meta-analysis combining trial findings with two previous ones. SETTING: Twenty-four English hospital antenatal clinics. PARTICIPANTS: A total of 1002 pregnant women who were ≥16 years old, were ≤25 weeks gestation and smoked ≥1 daily cigarette and accepted information on cessation with no requirement to set quit dates. INTERVENTIONS: UC or UC plus 'MiQuit': 12 weeks of tailored, smoking cessation text messages focussed on inducing and aiding cessation. MEASUREMENTS: Primary outcome: biochemically validated cessation between 4 weeks after randomisation and late pregnancy. SECONDARY OUTCOMES: shorter and non-validated abstinence periods, pregnancy outcomes and incremental cost-effectiveness ratios. FINDINGS: RCT: cessation was 5.19% (26/501) and 4.59% (23/501) in MiQuit and UC groups (adjusted odds ratio [adj OR] for quitting with MiQuit versus UC, 95% CI = 1.15 [0.65-2.04]); other abstinence findings were similar, with higher point estimates. Primary outcome ascertainment was 61.7% (309) and 67.3% (337) in MiQuit and UC groups with 71.1% (54/76) and 69.5% (41/59) abstinence validation rates, respectively. Pregnancy outcomes were similar and the incremental cost per quality-adjusted life year was -£1118 (95% CI = -£4806-£1911). More MiQuit group women reported making at least one quit attempt (adj OR [95% CI]) for making an attempt, 1.50 (1.07-2.09). TSA meta-analysis: this found no significant difference in prolonged abstinence between MiQuit and UC (pooled OR = 1.49, adjusted 95% CI = 0.62-3.60). CONCLUSIONS: Irrespective of whether they want to try quitting, when offered a tailored, self-help, text message stop smoking programme for pregnancy (MiQuit) as an adjunct to usual care, pregnant women are not more likely to stop smoking until childbirth but they report more attempts at stopping smoking

Towards constructivism: Investigating students' perceptions and learning as a result of using an online environment

The effects of changing to an online delivery mechanism within a third year, undergraduate, module have been evaluated against the lecturing staff's intended move towards a student-centred, constructivist learning approach. It has been suggested that this type of delivery can increase critical thinking and active learning for students. In the study described in this paper, qualitative analytical techniques were used in order to explore students' experiences of online delivery. The study addressed their perceptions about online methods as well as the educational implications of their patterns of usage of online resources. The findings suggest that students were quick to overcome anxieties about online learning but generally did not develop any significant degree of discussion. It is argued that a move to online delivery needs a greater attention to design and development of facilitator skills than has been previously recognized

Vacuum current emission and initiation in an LaB6 hollow cathode

This paper presents the first investigation of pre-ignition currents and the ignition process in an LaB6 hollow cathode running on krypton propellant. Vacuum and pre-ignition currents are found to be consistent with space charge limited behaviour. A novel, low power ignition strategy with the potential to reduce insert and orifice erosion is also shown

Unpacking pathways to diversified livelihoods from projects in Pacific Island coastal fisheries

Livelihood diversification has become an integral focus of policies and investments aiming to reduce poverty, vulnerability, and pressure on fishery resources in coastal communities around the globe. In this regard, coastal fisheries in the Pacific Islands have long been a sector where livelihood diversification has featured prominently. Yet, despite the widespread promotion and international investment in this strategy, the ability of externally funded livelihood diversification projects to facilitate improved resource management and rural development outcomes often remains inconsistent. We argue these inconsistencies can be attributed to a conceptual ambiguity stemming from a lack of attention and awareness to the complexity of livelihood diversification. There is still much to learn about the process of livelihood diversification, both in its theoretical conceptualizations and its practical applications. Herein, we utilize a common diversity framework to clarify some of this ambiguity by distinguishing three diversification pathways. These pathways are illustrated using an ideal–typical Pacific Island coastal household and supported by examples provided in the literature that detail livelihood diversification projects in the Pacific. Through this perspective, we seek a more nuanced understanding of what is meant within the policy and practice goal of livelihood diversification. Thereby enabling more targeted and deliberate planning for development investments that facilitates outcomes in support of sustainable livelihoods