99 research outputs found
The validity and reliability of the exposure index as a metric for estimating the radiation dose to the patient
Introduction
With the introduction of digital radiography, the feedback between image quality and over-exposure has been partly lost which in some cases has led to a steady increase in dose. Over the years the introduction of exposure index (EI) has been used to resolve this phenomenon referred to as ‘dose creep’. Even though EI is often vendor specific it is always a related of the radiation exposure to the detector. Due to the nature of this relationship EI can also be used as a patient dose indicator, however this is not widely investigated in literature.
Methods
A total of 420 dose-area-product (DAP) and EI measurements were taken whilst varying kVp, mAs and body habitus on two different anthropomorphic phantoms (pelvis and chest). Using linear regression, the correlation between EI and DAP were examined. Additionally, two separate region of interest (ROI) placements/per phantom where examined in order to research any effect on EI.
Results
When dividing the data into subsets, a strong correlation between EI and DAP was shown with all R-squared values > 0.987. Comparison between the ROI placements showed a significant difference between EIs for both placements.
Conclusion
This research shows a clear relationship between EI and radiation dose which is dependent on a wide variety of factors such as ROI placement, body habitus. In addition, pathology and manufacturer specific EI’s are likely to be of influence as well.
Implications for practice
The combination of DAP and EI might be used as a patient dose indicator. However, the influencing factors as mentioned in the conclusion should be considered and examined before implementation
Combining quantum and classical density functional theory for ion-electron mixtures
We combine techniques from quantum and from classical density functional
theory (DFT) to describe electron-ion mixtures. For homogeneous systems, we
show how to calculate ion-ion and ion-electron correlation functions within
Chihara's quantum hypernetted chain approximation, which we derive within a DFT
formulation. We also sketch out how to apply the DFT formulation to
inhomogeneous electron-ion mixtures, and use this to study the electron
distribution at the liquid-solid interface of Al.Comment: to be published in J. Non-Cryst. Solids, LAM 11 special issu
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Developmental trajectories of infants with multiplex family risk for Autism: a Baby Siblings Research Consortium Study
Importance: Autism spectrum disorder (ASD) is a neurodevelopmental disorder associated with
different genetic etiologies. Prospective examination of familial-risk infants informs
understanding of developmental trajectories preceding ASD diagnosis, potentially improving
early detection.
Objective: Compare outcomes and trajectories associated with varying familial risk for ASD
across first 3 years of life.
Design and Setting: Longitudinal, prospective observational study. Data from 11 sites in Baby
Siblings Research Consortium (BSRC) database included. Data collected between 2003-2015.
Infants followed for 3 years. Analyses conducted in 2018.
Participants: Of initial 1,008 infants from BSRC database, 573 removed due to missing
necessary data, diagnostic discrepancies, or only one older sibling. 435 younger siblings of
children with ASD included; 355 from single-incidence families (1 sibling with ASD and 1+
sibling without ASD) and 80 from multiplex families (2+ siblings with ASD). No group
differences in major demographics.
Exposure: Number of ASD-siblings.
Main Outcomes and Measures: Outcomes included ASD symptoms, cognitive abilities, and
adaptive skills. Diagnosis (ASD/no-ASD) given at 36-month outcome. No-ASD group classified
as atypical (developmental delays and/or social-communication concerns) or typical for some
analyses. Generalized linear mixed models examined developmental trajectories by ASD
outcome and familial-risk group.
Results: In the 435 analyzed participants (age range at outcome: 32-43 months; 57% male),
children from multiplex families were more likely than those from single-incidence families to
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be classified as ASD (36% vs. 16%, p<.001) and less likely as typical (33% vs. 57%, p<.001),
with similar rates of atypical classifications (31% vs. 27%, p=.49). No differences in ASD
symptoms between multiplex and single-incidence groups, after controlling for ASD outcome
(p=.18). During infancy, differences in cognitive and adaptive abilities observed based upon
ASD outcome in single-incidence group only (ps<.001-.04). At 36 months, multiplex/no-ASD
group had lower cognitive abilities than single-incidence/no-ASD group (p=.02), and multiplex
had lower adaptive abilities than single-incidence, after controlling for ASD outcome (p=.02).
Conclusions and Relevance: Infants with a multiplex family history of ASD should be
monitored early and often and referred for early intervention at the first sign of concern. Direct
examination of genetic contributions to neurodevelopmental phenotypes in infants with familial
risk for ASD is needed
A História da Alimentação: balizas historiográficas
Os M. pretenderam traçar um quadro da História da Alimentação, não como um novo ramo epistemológico da disciplina, mas como um campo em desenvolvimento de práticas e atividades especializadas, incluindo pesquisa, formação, publicações, associações, encontros acadêmicos, etc. Um breve relato das condições em que tal campo se assentou faz-se preceder de um panorama dos estudos de alimentação e temas correia tos, em geral, segundo cinco abardagens Ia biológica, a econômica, a social, a cultural e a filosófica!, assim como da identificação das contribuições mais relevantes da Antropologia, Arqueologia, Sociologia e Geografia. A fim de comentar a multiforme e volumosa bibliografia histórica, foi ela organizada segundo critérios morfológicos. A seguir, alguns tópicos importantes mereceram tratamento à parte: a fome, o alimento e o domÃnio religioso, as descobertas européias e a difusão mundial de alimentos, gosto e gastronomia. O artigo se encerra com um rápido balanço crÃtico da historiografia brasileira sobre o tema
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