Demonstration of the Effect of Generic Anatomical Divisions versus Clinical Protocols on Computed Tomography Dose Estimates and Risk Burden

Objective: Choosing to undertake a CT scan relies on balancing risk versus benefit, however risks associated with CT scanning have generally been limited to broad anatomical locations, which do not provided adequate information to evaluate risk against benefit. Our study aimed to determine differences in radiation dose and risk estimates associated with modern CT scanning examinations when computed for clinical protocols compared with those using anatomical area. Methods: Technical data were extracted from a tertiary hospital Picture Archiving Communication System for random samples of 20–40 CT examinations per adult clinical CT protocol. Organ and whole body radiation dose were calculated using ImPACT Monte Carlo simulation software and cancer incidence and mortality estimated using BEIR VII age and gender specific lifetime attributable risk weights. Results: Thirty four unique CT protocols were identified by our study. When grouped according to anatomic area the radiation dose varied substantially, particularly for abdominal protocols. The total estimated number of incident cancers and cancer related deaths using the mean dose of anatomical area were 86 and 69 respectively. Using more specific protocol doses the estimates rose to 214 and 138 incident cancers and cancer related deaths, at least doubling the burden estimated. Conclusions: Modern CT scanning produces a greater diversity of effective doses than much of the literature describes; where a lack of focus on actual scanning protocols has produced estimates that do not reflect the range and complexity of modern CT practice. To allow clinicians, patients and policy makers to make informed risk versus benefit decisions the individual and population level risks associated with modern CT practices are essential

Robust Poisson Surface Reconstruction

Abstract. We propose a method to reconstruct surfaces from oriented point clouds with non-uniform sampling and noise by formulating the problem as a convex minimization that reconstructs the indicator func-tion of the surface’s interior. Compared to previous models, our recon-struction is robust to noise and outliers because it substitutes the least-squares fidelity term by a robust Huber penalty; this allows to recover sharp corners and avoids the shrinking bias of least squares. We choose an implicit parametrization to reconstruct surfaces of unknown topology and close large gaps in the point cloud. For an efficient representation, we approximate the implicit function by a hierarchy of locally supported basis elements adapted to the geometry of the surface. Unlike ad-hoc bases over an octree, our hierarchical B-splines from isogeometric analysis locally adapt the mesh and degree of the splines during reconstruction. The hi-erarchical structure of the basis speeds-up the minimization and efficiently represents clustered data. We also advocate for convex optimization, in-stead isogeometric finite-element techniques, to efficiently solve the min-imization and allow for non-differentiable functionals. Experiments show state-of-the-art performance within a more flexible framework.

Constraints on Nucleon Decay via "Invisible" Modes from the Sudbury Neutrino Observatory

Data from the Sudbury Neutrino Observatory have been used to constrain the lifetime for nucleon decay to ``invisible'' modes, such as n -> 3 nu. The analysis was based on a search for gamma-rays from the de-excitation of the residual nucleus that would result from the disappearance of either a proton or neutron from O16. A limit of tau_inv > 2 x 10^{29} years is obtained at 90% confidence for either neutron or proton decay modes. This is about an order of magnitude more stringent than previous constraints on invisible proton decay modes and 400 times more stringent than similar neutron modes.Comment: Update includes missing efficiency factor (limits change by factor of 2) Submitted to Physical Review Letter

Cardiovascular imaging 2010 in the International Journal of Cardiovascular Imaging

Cardiovascular Aspects of Radiolog

Estimation of Isolation Times of the Island Species in the Drosophila simulans Complex from Multilocus DNA Sequence Data

Background: The Drosophila simulans species complex continues to serve as an important model system for the study of new species formation. The complex is comprised of the cosmopolitan species, D. simulans, and two island endemics, D. mauritiana and D. sechellia. A substantial amount of effort has gone into reconstructing the natural history of the complex, in part to infer the context in which functional divergence among the species has arisen. In this regard, a key parameter to be estimated is the initial isolation time (t) of each island species. Loci in regions of low recombination have lower divergence within the complex than do other loci, yet divergence from D. melanogaster is similar for both classes. This might reflect gene flow of the lowrecombination loci subsequent to initial isolation, but it might also reflect differential effects of changing population size on the two recombination classes of loci when the low-recombination loci are subject to genetic hitchhiking or pseudohitchhiking Methodology/Principal Findings: New DNA sequence variation data for 17 loci corroborate the prior observation from 13 loci that DNA sequence divergence is reduced in genes of low recombination. Two models are presented to estimate t and other relevant parameters (substitution rate correction factors in lineages leading to the island species and, in the case of the 4-parameter model, the ratio of ancestral to extant effective population size) from the multilocus DNA sequence data. Conclusions/Significance: In general, it appears that both island species were isolated at about the same time, here estimated at,250,000 years ago. It also appears that the difference in divergence patterns of genes in regions of low an

Extragalactic Radio Continuum Surveys and the Transformation of Radio Astronomy

Next-generation radio surveys are about to transform radio astronomy by discovering and studying tens of millions of previously unknown radio sources. These surveys will provide new insights to understand the evolution of galaxies, measuring the evolution of the cosmic star formation rate, and rivalling traditional techniques in the measurement of fundamental cosmological parameters. By observing a new volume of observational parameter space, they are also likely to discover unexpected new phenomena. This review traces the evolution of extragalactic radio continuum surveys from the earliest days of radio astronomy to the present, and identifies the challenges that must be overcome to achieve this transformational change.Comment: To be published in Nature Astronomy 18 Sept 201

Evolutionary Breakpoints in the Gibbon Suggest Association between Cytosine Methylation and Karyotype Evolution

Gibbon species have accumulated an unusually high number of chromosomal changes since diverging from the common hominoid ancestor 15–18 million years ago. The cause of this increased rate of chromosomal rearrangements is not known, nor is it known if genome architecture has a role. To address this question, we analyzed sequences spanning 57 breaks of synteny between northern white-cheeked gibbons (Nomascus l. leucogenys) and humans. We find that the breakpoint regions are enriched in segmental duplications and repeats, with Alu elements being the most abundant. Alus located near the gibbon breakpoints (<150 bp) have a higher CpG content than other Alus. Bisulphite allelic sequencing reveals that these gibbon Alus have a lower average density of methylated cytosine that their human orthologues. The finding of higher CpG content and lower average CpG methylation suggests that the gibbon Alu elements are epigenetically distinct from their human orthologues. The association between undermethylation and chromosomal rearrangement in gibbons suggests a correlation between epigenetic state and structural genome variation in evolution

Fibromyalgia and neuropathic pain - differences and similarities. A comparison of 3057 patients with diabetic painful neuropathy and fibromyalgia

<p>Abstract</p> <p>Background</p> <p>Patients with diabetic neuropathy (DPN) and fibromyalgia differ substantially in pathogenetic factors and the spatial distribution of the perceived pain. We questioned whether, despite these obvious differences, similar abnormal sensory complaints and pain qualities exist in both entities. We hypothesized that similar sensory symptoms might be associated with similar mechanisms of pain generation. The aims were (1) to compare epidemiological features and co-morbidities and (2) to identify similarities and differences of sensory symptoms in both entities.</p> <p>Methods</p> <p>The present multi-center study compares epidemiological data and sensory symptoms of a large cohort of 1434 fibromyalgia patients and 1623 patients with painful diabetic neuropathy. Data acquisition included standard demographic questions and self-report questionnaires (MOS sleep scale, PHQ-9, Pain<it>DETECT</it>). To identify subgroups of patients with characteristic combinations of symptoms (sensory profiles) a cluster analysis was performed using all patients in both cohorts.</p> <p>Results</p> <p>Significant differences in co-morbidities (depression, sleep disturbance) were found between both disorders. Patients of both aetiologies chose very similar descriptors to characterize their sensory perceptions. Burning pain, prickling and touch-evoked allodynia were present in the same frequency. Five subgroups with distinct symptom profiles could be detected. Two of the subgroups were characteristic for fibromyalgia whereas one profile occurred predominantly in DPN patients. Two profiles were found frequently in patients of both entities (20-35%).</p> <p>Conclusions</p> <p>DPN and fibromyalgia patients experience very similar sensory phenomena. The combination of sensory symptoms - the sensory profile - is in most cases distinct and almost unique for each one of the two entities indicating aetiology-specific mechanisms of symptom generation. Beside the unique aetiology-specific sensory profiles an overlap of sensory profiles can be found in 20-35% of patients of both aetiologies.</p

Clonal Differences between Non-Typhoidal Salmonella (NTS) Recovered from Children and Animals Living in Close Contact in The Gambia

Salmonellosis is a neglected tropical disease causing serious dysentery and septicaemia particularly in young infants, elderly and immunocompromised individuals such as HIV patients and associated with substantial mortality in developing countries. Salmonellosis also constitutes a major public health problem as it is considered the most widespread bacterial zoonosis of food origin throughout the world. Many epidemiological data exist from developed countries concerning transmission of Non-Typhoidal Salmonella (NTS) but few are available from developing countries. In addition few studies in sub-Saharan Africa have considered the interface between humans and their environment in relation to animals present in the household and food hygiene. This study describes the prevalence of NTS among fourteen Gambian children and 210 domestic animals living in close proximity (household) to the children in a rural setting in The Gambia. We found that the domestic animals living in the same household as patients carried different NTS serovar and genotypes; indicating that zoonotic transmission does not occur in our setting. This study provides baseline data for future studies of transmission of NTS in rural Africa