Automated volumetric analysis of structural MR imaging allows quantitative assessment of brain atrophy in neurodegenerative disorders. We compared the brain segmentation performance of the AI-Rad ...Companion brain MR imaging software against an in-house FreeSurfer 7.1.1/Individual Longitudinal Participant pipeline.
T1-weighted images of 45 participants with de novo memory symptoms were selected from the OASIS-4 database and analyzed through the AI-Rad Companion brain MR imaging tool and the FreeSurfer 7.1.1/Individual Longitudinal Participant pipeline. Correlation, agreement, and consistency between the 2 tools were compared among the absolute, normalized, and standardized volumes. Final reports generated by each tool were used to compare the rates of detection of abnormality and the compatibility of radiologic impressions made using each tool, compared with the clinical diagnoses.
We observed strong correlation, moderate consistency, and poor agreement between absolute volumes of the main cortical lobes and subcortical structures measured by the AI-Rad Companion brain MR imaging tool compared with FreeSurfer. The strength of the correlations increased after normalizing the measurements to the total intracranial volume. Standardized measurements differed significantly between the 2 tools, likely owing to differences in the normative data sets used to calibrate each tool. When considering the FreeSurfer 7.1.1/Individual Longitudinal Participant pipeline as a reference standard, the AI-Rad Companion brain MR imaging tool had a specificity of 90.6%-100% and a sensitivity of 64.3%-100% in detecting volumetric abnormalities. There was no difference between the rate of compatibility of radiologic and clinical impressions when using the 2 tools.
The AI-Rad Companion brain MR imaging tool reliably detects atrophy in cortical and subcortical regions implicated in the differential diagnosis of dementia.
To characterise the corticoreticular pathway (CRP) in a case–control cohort of adolescent idiopathic scoliosis (AIS) patients using high-resolution slice-accelerated readout-segmented echo-planar ...diffusion tensor imaging (DTI) to enhance the discrimination of small brainstem nuclei in comparison to automated whole-brain volumetry and tractography and their clinical correlates.
Thirty-four participants (16 AIS patients, 18 healthy controls) underwent clinical and orthopaedic assessments and brain magnetic resonance imaging (MRI) on a 3 T MRI machine. Automated whole-brain volume-based morphometry, tract-based spatial statistics analysis, and manual CRP tractography by two independent raters were performed. Intra-rater and inter-rater agreement of DTI metrics from CRP tractography were assessed by intraclass correlation coefficient. Normalised structural brain volumes and DTI metrics were compared between groups using Student's t-tests. Linear correlation analysis between imaging parameters and clinical scores was also performed.
AIS patients demonstrated a significantly larger pons volume compared to controls (p=0.006). Significant inter-side CRP differences in mean (p=0.02) and axial diffusivity (p=0.01) were found in patients only. Asymmetry in CRP fractional anisotropy significantly correlated with the Cobb angle (p=0.03).
Relative pontine hypertrophy and asymmetry in CRP DTI metrics suggest central supranuclear inter-hemispheric imbalance in AIS, and support the role of the CRP in axial muscle tone. Longitudinal evaluation of CRP DTI metrics in the prediction of AIS progression may be clinically relevant.
•The corticoreticular pathway (CRP) controls truncal muscle tone and posture.•RESOLVE DTI enhances discrimination of small brainstem nuclei for CRP tractography.•AIS patients demonstrated a significantly larger pons volume compared to controls.•Inter-side differences in CRP mean and axial diffusivity are only found in patients.•CRP fractional anisotropy correlated with the Cobb angle in AIS patients.
MEMS frequency references and MEMS vibrating sensors, based on a resonator vibrating at its resonance frequency, offer interesting prospects in terms of miniaturization, cost and precision but their ...design optimization is difficult because multiple physical domains must be taken into account, as well as the associated nonlinearities that limit the carrier power. Once the model is set up, the simulation of the accurate phase noise that limits the sensor’s precision is also a difficult matter. In this work, a behavioural model in Verilog-A is presented, that allows multi-physic simulations : mechanical, piezoelectric, electrostatic and electrical analytic descriptions including the associated nonlinear behaviours are derived. Transient and phase noise analysis are then performed with this model through the dedicated CADENCE PSS (Periodic Steady State) and Pnoise (Periodic Noise) analysis and compared to the analytical expression of the nonlinear critical amplitude, and to the standard Leeson analytical expression for phase noise. This work is the first step to improve the performances of such MEMS oscillators.
The nature of b-quark jet hadronisation has been investigated using data taken at the Z peak by the DELPHI detector at LEP. Two complementary methods are used to reconstruct the energy of weakly ...decaying b-hadrons,
. The average value of
is measured to be 0.699±0.011. The resulting
distribution is then analysed in the framework of two choices for the perturbative contribution (parton shower and Next to Leading Log QCD calculation) in order to extract measurements of the non-perturbative contribution to be used in studies of b-hadron production in other experimental environments than LEP. In the parton shower framework, data favour the Lund model ansatz and corresponding values of its parameters have been determined within PYTHIA 6.156 from DELPHI data:
with a correlation factor
ρ
=92.2%.
Combining the data on the b-quark fragmentation distributions with those obtained at the Z peak by ALEPH, OPAL and SLD, the average value of
is found to be 0.7092±0.0025 and the non-perturbative fragmentation component is extracted. Using the combined distribution, a better determination of the Lund parameters is also obtained:
with a correlation factor
ρ
=92.6%.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A substantial part of the mineralogical and chemical heterogeneity of clay-poor sands, at the bed scale, results from tractive redistribution of the grains in the bedload. Since coarse and light ...particles are more easily entrained than denser and smaller heavy minerals, the latter commonly concentrate in grain scale lags, that alternate with sand depleted in these minerals. When sampled and analysed at the centimetre scale, this primary heterogeneity translates into nice geochemical covariations between the minor/trace elements that concentrate in some heavy minerals (Zr, Ti, P, Cr, V, Y, Ce among others). Regressing these variations allow us to derive two chemical fingerprints of the sand: one records the proportions between some heavy minerals, the other the average composition of framework grains, i.e., a sand composition corrected from the contribution of heavy minerals. Both relate to provenance and allow different sand beds to be compared in appropriate spider diagrams.
The construction of these diagrams, their potential use and their limitations are discussed using two contrasting examples. Continental channel sandstones from the Ravenscar Group (middle Jurassic, Yorkshire, UK) illustrate how these geochemical fingerprints vary from the local to the Group scales and how robust they are against diagenetic overprint. At Ravenscar, the Zr vs. Ti, V, Cr covariations record the presence of Ti oxides and magnetite together with zircon and of volcanic lithoclasts at the deposition stage, despite a high degree of diagenetic alteration. Overbank sandstones (lateral to channels) from the deep marine Grès d'Annot Formation (Eocene–Oligocene, Alps) illustrates how apatite and monazite delivered by a dominantly granitic source generate covariations between Zr and P, Y, Ce and Th contents with characteristically steep slopes.
Single photons detected by the DELPHI experiment at LEP2 in the years 1997–2000 are reanalysed to investigate the existence of a single extra dimension in a modified ADD scenario with slightly warped ...large extra dimensions. The data collected at centre-of-mass energies between 180 and 209 GeV for an integrated luminosity of ∼650 pb
−1
agree with the predictions of the Standard Model and allow a limit to be set on graviton emission in one large extra dimension. The limit obtained on the fundamental mass scale
M
D
is 1.69 TeV/
c
2
at 95% CL, with an expected limit of 1.71 TeV/
c
2
.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Performance of a Multigap RPC prototype for the LHCb Muon system Colrain, P; Corti, G; de Paula, L ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2000, Letnik:
456, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Several technologies are under consideration for the muon system of the LHCb experiment. Resistive Plate Chambers (RPCs) are one of the favourite candidates for the outer areas where the particle ...fluxes are expected to be at most some kHz/cm
2. This work describes the results obtained with a Multigap RPC prototype under various beam conditions at the CERN facilities.
Tau-pair production in the process \(\ensuremath{\mathrm{e}^ + \mathrm{e}^- \rightarrow \mathrm{e}^ + \mathrm{e}^-\tau^ + \tau^-}\) was studied using data collected by the DELPHI experiment at LEP2 ...during the years 1997 - 2000. The corresponding integrated luminosity is 650 pb-1. The values of the cross-section obtained are found to be in agreement with QED predictions. Limits on the anomalous magnetic and electric dipole moments of the tau lepton are deduced.
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