890 research outputs found
Diagnosis of vertebral fractures in children: is a simplified algorithm-based qualitative technique reliable?
Background Identification of osteoporotic vertebral fractures
allows treatment opportunity reducing future risk. There is no
agreed standardised method for diagnosing paediatric vertebral
fractures.
Objective To evaluate the precision of a modified adult
algorithm-based qualitative (ABQ) technique, applicable to
children with primary or secondary osteoporosis.
Materials and methods Three radiologists independently
assessed lateral spine radiographs of 50 children with
suspected reduction in bone mineral density using a modified
ABQ scoring system and following simplification to include
only clinically relevant parameters, a simplified ABQ score. A
final consensus of all observers using simplified ABQ was
performed as a reference standard for fracture characterisation.
Kappa was calculated for interobserver agreement of the
components of both scoring systems and intraobserver agreement
of simplified ABQ based on a second read of 29 randomly
selected images.
Results Interobserver Kappa for modified ABQ scoring for
fracture detection, severity and shape ranged from 0.34 to
0.49 Kappa for abnormal endplate and position assessment
was 0.27 to 0.38. Inter- and intraobserver Kappa for simplified
ABQ scoring for fracture detection and grade ranged from
0.37 to 0.46 and 0.45 to 0.56, respectively. Inter- and
intraobserver Kappa for affected endplate ranged from 0.31
to 0.41 and 0.45 to 0.51, respectively. Subjectively, observers’
felt simplified ABQ was easier and less time-consuming.
Conclusion Observer reliability of modified and simplified
ABQ was similar, with slight to moderate agreement for fracture
detection and grade/severity. Due to subjective preference
for simplified ABQ, we suggest its use as a semi-objective
measure of diagnosing paediatric vertebral fracture
Necessary Optimality Conditions for Higher-Order Infinite Horizon Variational Problems on Time Scales
We obtain Euler-Lagrange and transversality optimality conditions for
higher-order infinite horizon variational problems on a time scale. The new
necessary optimality conditions improve the classical results both in the
continuous and discrete settings: our results seem new and interesting even in
the particular cases when the time scale is the set of real numbers or the set
of integers.Comment: This is a preprint of a paper whose final and definite form will
appear in Journal of Optimization Theory and Applications (JOTA). Paper
submitted 17-Nov-2011; revised 24-March-2012 and 10-April-2012; accepted for
publication 15-April-201
Transversality Conditions for Infinite Horizon Variational Problems on Time Scales
We consider problems of the calculus of variations on unbounded time scales.
We prove the validity of the Euler-Lagrange equation on time scales for
infinite horizon problems, and a new transversality condition.Comment: Submitted 6-October-2009; Accepted 19-March-2010 in revised form; for
publication in "Optimization Letters"
Diagnostic performance of morphometric vertebral fracture analysis (MXA) in children using a 33-point software program
Background
There is significant inter and intraobserver variability in diagnosing vertebral fractures in children.
Purpose
We aimed to evaluate the diagnostic accuracy of morphometric vertebral fracture analysis (MXA) using a 33-point software program designed for adults, on dual-energy x-ray absorptiometry (DXA) images of children.
Materials and methods
Lateral spine DXA images of 420 children aged between 5 and 18 years were retrospectively reviewed. Vertebral fracture assessment (VFA) by an expert pediatric radiologist using Genant's semiquantitative scoring system served as the gold standard. All 420 DXA scans were analyzed by a trained radiographer, using semi-automated software (33-point morphometry). VFA of a random sample of 100 DXA was performed by an experienced pediatric clinical scientist. MXA of a random sample of 30 DXA images were analyzed by three pediatric radiologists and the pediatric clinical scientist. Diagnostic accuracy and inter and intraobserver agreement (kappa statistics) were calculated.
Results
Overall sensitivity, specificity, false positive (FP) and false negative (FN) rates for the radiographer using the MXA software were 80%, 90%, 10%, and 20% respectively and for mild fractures alone were 46%, 92%, 8%, and 54% respectively. Overall sensitivity, specificity, FP, and FN rates for the four additional observers using MXA were 89%, 79%, 21%, and 11% respectively and for mild fractures alone were 36%, 86%, 14%, and 64% respectively. Agreement between two expert observers was fair to good for VFA and MXA [kappa = 0·29 to 0·76 (95% CI: 0·17–0·88) and 0·29 to 0·69 (95% CI: 0·17–0·83)] respectively.
Conclusion
MXA using a 33-point technique developed for adults is not a reliable method for the identification of mild vertebral fractures in children. A pediatric standard is required which not only incorporates specific vertebral body height ratios but also the age-related physiological changes in vertebral shape that occur throughout childhood
Data Analysis Challenges for the Einstein Telescope
The Einstein Telescope is a proposed third generation gravitational wave
detector that will operate in the region of 1 Hz to a few kHz. As well as the
inspiral of compact binaries composed of neutron stars or black holes, the
lower frequency cut-off of the detector will open the window to a number of new
sources. These will include the end stage of inspirals, plus merger and
ringdown of intermediate mass black holes, where the masses of the component
bodies are on the order of a few hundred solar masses. There is also the
possibility of observing intermediate mass ratio inspirals, where a stellar
mass compact object inspirals into a black hole which is a few hundred to a few
thousand times more massive. In this article, we investigate some of the data
analysis challenges for the Einstein Telescope such as the effects of increased
source number, the need for more accurate waveform models and the some of the
computational issues that a data analysis strategy might face.Comment: 18 pages, Invited review for Einstein Telescope special edition of
GR
The Physics of turbulent and dynamically unstable Herbig-Haro jets
The overall properties of the Herbig-Haro objects such as centerline
velocity, transversal profile of velocity, flow of mass and energy are
explained adopting two models for the turbulent jet. The complex shapes of the
Herbig-Haro objects, such as the arc in HH34 can be explained introducing the
combination of different kinematic effects such as velocity behavior along the
main direction of the jet and the velocity of the star in the interstellar
medium. The behavior of the intensity or brightness of the line of emission is
explored in three different cases : transversal 1D cut, longitudinal 1D cut and
2D map. An analytical explanation for the enhancement in intensity or
brightness such as usually modeled by the bow shock is given by a careful
analysis of the geometrical properties of the torus.Comment: 17 pages, 10 figures. Accepted for publication in Astrophysics &
Spac
Inter- and intra-observer reliability of contrast-enhanced magnetic resonance imaging parameters in children with suspected juvenile idiopathic arthritis of the hip
BACKGROUND: Previous work at our institution demonstrated discrepancies between radiologists in interpretation of contrast-enhanced magnetic resonance imaging (MRI) in suspected hip arthritis. OBJECTIVE: To assess inter- and intra-observer reliability of selected MRI parameters (effusion, marrow oedema and synovial thickness and enhancement) used in the diagnosis of juvenile idiopathic arthritis. MATERIALS AND METHODS: A retrospective cohort study was conducted of patients with confirmed or suspected juvenile idiopathic arthritis who underwent hip contrast-enhanced MRI between January 2011 and September 2014. Three pediatric musculoskeletal radiologists independently assessed all scans for effusion, marrow oedema, measurement of synovial thickness, synovial enhancement and subjective assessment of synovium. Categorical variables were analysed using the Cohen Îş, and measurement using Bland-Altman plots. RESULTS: Eighty patients were included. Interobserver reliability was moderate for effusion (Îş=0.5-0.7), marrow oedema (Îş=0.6), subjective synovial assessment (Îş=0.4-0.5) and synovial enhancement (Îş=0.1-0.5). Intra-observer reliability was highest for marrow oedema (Îş=0.6-0.8) and lowest for effusion (Îş=0.4-0.7). Intra-observer reliability for synovial enhancement (Îş= -0.7-0.8) and subjective synovial assessment (Îş=0.4-1.0) ranged from poor to excellent. For synovial thickness, intra- and interobserver Bland-Altman plots were well clustered around the mean suggesting good agreement. CONCLUSION: There were large differences across variables and only moderate agreement between observers. The most reliable parameters were presence of joint effusion and bone marrow oedema and subjective assessment of synovium
Global QCD Analysis and the CTEQ Parton Distributions
The CTEQ program for the determination of parton distributions through a
global QCD analysis of data for various hard scattering processes is fully
described. A new set of distributions, CTEQ3, incorporating several new types
of data is reported and compared to the two previous sets of CTEQ
distributions. Comparison with current data is discussed in some detail. The
remaining uncertainties in the parton distributions and methods to further
reduce them are assessed. Comparisons with the results of other global analyses
are also presented.Comment: (Change in Latex style only: 2up style removed since many don't have
it.) 35 pages, 23 figures separately submitted as uuencoded compressed
ps-file; Michigan State Report # MSU-HEP/41024 and CTEQ 40
- …