427 research outputs found
Atherosclerotic carotid plaque composition: a 3T and 7T MRI-histology correlation study
Background and Purpose
Carotid artery atherosclerotic plaque composition may influence plaque stability and risk of
thromboembolic events, and non-invasive plaque imaging may therefore permit risk
stratification for clinical management. Plaque composition was compared using non-invasive
in-vivo (3T) and ex-vivo (7T) MRI and histopathological examination.
Methods
Thirty three endarterectomy cross sections, from 13 patients, were studied. The datasets
consisted of in-vivo 3T MRI, ex-vivo 7T MRI and histopathology. Semi-automated
segmentation methods were used to measure areas of different plaque components. Bland-
Altman plots and mean difference with 95% confidence interval were carried out.
Results
There was general quantitative agreement between areas derived from semi-automated
segmentation of MRI data and histology measurements. The mean differences and 95%
confidence bounds in the relative to total plaque area between 3T versus Histology were:
fibrous tissue 4.99 % (-4.56 to 14.56), lipid-rich/necrotic core (LR/NC) with haemorrhage -
1.81% (-14.11 to 10.48), LR/NC without haemorrhage -2.43% (-13.04 to 8.17), and
calcification -3.18% (-11.55 to 5.18). The mean differences and 95% confidence bounds in
the relative to total plaque area between 7T and histology were: fibrous tissue 3.17 % (-3.17
to 9.52), LR/NC with haemorrhage -0.55% (-9.06 to 7.95), LR/NC without haemorrhage -
12.62% (-19.8 to -5.45), and calcification -2.43% (-9.97 to 4.73).
Conclusions
This study provides evidence that semi-automated segmentation of 3T/7T MRI techniques
can help to determine atherosclerotic plaque composition. In particular, the high resolution of
ex-vivo 7T data was able to highlight greater detail in the atherosclerotic plaque composition.
High field MRI may therefore have advantages for in vivo carotid plaque MR imaging
Bianchi type II,III and V diagonal Einstein metrics re-visited
We present, for both minkowskian and euclidean signatures, short derivations
of the diagonal Einstein metrics for Bianchi type II, III and V. For the first
two cases we show the integrability of the geodesic flow while for the third
case a somewhat unusual bifurcation phenomenon takes place: for minkowskian
signature elliptic functions are essential in the metric while for euclidean
signature only elementary functions appear
Synthesis of Novel Peptide Inhibitors of Thrombin-induced Platelet Activation
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65762/1/j.1747-0285.2006.00442.x.pd
Practical application of direct electron detectors to EBSD mapping in 2D and 3D
The use of a direct electron detector for the simple acquisition of 2D electron backscatter diffraction (EBSD) maps and 3D EBSD datasets with a static sample geometry has been demonstrated in a focused ion beam scanning electron microscope. The small size and flexible connection of the Medipix direct electron detector enabled the mounting of sample and detector on the same stage at the short working distance required for the FIB. Comparison of 3D EBSD datasets acquired by this means and with conventional phosphor based EBSD detectors requiring sample movement showed that the former method with a static sample gave improved slice registration. However, for this sample detector configuration, significant heating by the detector caused sample drift. This drift and ion beam reheating both necessitated the use of fiducial marks to maintain stability during data acquisition
Double-Spin Asymmetry in the Cross Section for Exclusive rho^0 Production in Lepton-Proton Scattering
Evidence for a positive longitudinal double-spin asymmetry = 0.24
+-0.11 (stat) +-0.02 (syst) in the cross section for exclusive diffractive
rho^0(770) vector meson production in polarised lepton-proton scattering was
observed by the HERMES experiment. The longitudinally polarised 27.56 GeV HERA
positron beam was scattered off a longitudinally polarised pure hydrogen gas
target. The average invariant mass of the photon-proton system has a value of
= 4.9 GeV, while the average negative squared four-momentum of the virtual
photon is = 1.7 GeV^2. The ratio of the present result to the
corresponding spin asymmetry in inclusive deep-inelastic scattering is in
agreement with an early theoretical prediction based on the generalised vector
meson dominance model.Comment: 10 pages, 4 embedded figures, LaTe
The -dependence of the generalised Gerasimov-Drell-Hearn integral for the deuteron, proton and neutron
The Gerasimov-Drell-Hearn (GDH) sum rule connects the anomalous contribution
to the magnetic moment of the target nucleus with an energy-weighted integral
of the difference of the helicity-dependent photoabsorption cross sections. The
data collected by HERMES with a deuterium target are presented together with a
re-analysis of previous measurements on the proton. This provides a measurement
of the generalised GDH integral covering simultaneously the nucleon-resonance
and the deep inelastic scattering regions. The contribution of the
nucleon-resonance region is seen to decrease rapidly with increasing . The
DIS contribution is sizeable over the full measured range, even down to the
lowest measured . As expected, at higher the data are found to be in
agreement with previous measurements of the first moment of . From data on
the deuteron and proton, the GDH integral for the neutron has been derived and
the proton--neutron difference evaluated. This difference is found to satisfy
the fundamental Bjorken sum rule at GeV.Comment: 12 pages, 10 figure
Measurement of the Proton Spin Structure Function g1p with a Pure Hydrogen Target
A measurement of the proton spin structure function g1p(x,Q^2) in
deep-inelastic scattering is presented. The data were taken with the 27.6 GeV
longitudinally polarised positron beam at HERA incident on a longitudinally
polarised pure hydrogen gas target internal to the storage ring. The kinematic
range is 0.021<x<0.85 and 0.8 GeV^2<Q^2<20 GeV^2. The integral
Int_{0.021}^{0.85} g1p(x)dx evaluated at Q0^2 of 2.5 GeV^2 is
0.122+/-0.003(stat.)+/-0.010(syst.).Comment: 7 pages, 3 figures, 1 table, RevTeX late
Subleading-twist effects in single-spin asymmetries in semi-inclusive deep-inelastic scattering on a longitudinally polarized hydrogen target
Single-spin asymmetries in the semi-inclusive production of charged pions in
deep-inelastic scattering from transversely and longitudinally polarized proton
targets are combined to evaluate the subleading-twist contribution to the
longitudinal case. This contribution is significantly positive for (\pi^+)
mesons and dominates the asymmetries on a longitudinally polarized target
previously measured by \hermes. The subleading-twist contribution for (\pi^-)
mesons is found to be small
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