129 research outputs found
Description of regional mitral annular nonplanarity in healthy human subjects: A novel methodology
ObjectiveFinite-element analysis demonstrates that the nonplanar shape of the mitral annulus diminishes mitral leaflet stress. It has therefore been postulated that repair with annuloplasty rings that maintain the nonplanar shape of the annulus could increase repair durability. Although the global nonplanarity of the mitral annulus has been adequately characterized, design of such a ring requires a quantitative description of regional annular geometry. By using real-time 3-dimensional echocardiography in conjunction with available image processing software, we developed a methodology for describing regional annular geometry and applied it to the characterization of the normal human mitral annulus.MethodsFive healthy volunteers underwent mitral valve imaging with real-time 3-dimensional echocardiography. Regional annular height was calculated at 36 evenly spaced intervals.ResultsMaximal annular height/commissural width ratio was found to occur at the midpoint of the anterior annulus in all cases. These values averaged 26% ± 3.1%, whereas those for the midposterior annulus averaged 18% ± 3.0%. The average commissural width was 35.2 ± 6.0 mm. Although substantial spatial heterogeneity was observed, regional annular height at a given rotational position was highly conserved among subjects when normalized to commissural width.ConclusionsThese quantitative imaging and analytic techniques demonstrate that the normal human mitral annulus is regionally heterogeneous in its nonplanarity, and they establish a means of describing annular geometry at a regional level. With wider application, these techniques may be used both to characterize pathologic annular geometry and to optimize the design of mitral valve annuloplasty devices
Surgical treatment of ischemic mitral regurgitation might not influence ventricular remodeling
ObjectivesSurgical treatment for ischemic mitral regurgitation has become more aggressive. However, no clinical study has demonstrated that surgical correction of chronic ischemic mitral regurgitation improves survival. We used 4 well-developed ovine models of postinfarction left ventricular remodeling to test the hypothesis that ischemic mitral regurgitation does not significantly contribute to postinfarction left ventricular remodeling.MethodsInfarction of 21% to 24% of the left ventricular mass was induced by means of coronary ligation in 77 sheep. Infarctions varied only by anatomic location in the left ventricle: anteroapical, n = 26; anterobasal, n = 16; laterobasal, n = 9; and posterobasal, n = 20. Six additional sheep had ring annuloplasty before posterobasal infarction. End-systolic and end-diastolic left ventricular volume, end-systolic muscle-to-cavity area ratio, left ventricular sphericity, ejection fraction, and degree of ischemic mitral regurgitation, as determined by means of quantitative echocardiography, were assessed before infarction and at 2, 5, and 8 weeks after infarction.ResultsAll infarcts resulted in significant postinfarction remodeling and decreased ejection fraction. Anteroapical infarcts lead to left ventricular aneurysms. Only posterobasal infarcts caused severe and progressive ischemic mitral regurgitation. Remodeling because of posterobasal infarcts was not more severe than that caused by infarcts at other locations. Furthermore, prophylactic annuloplasty prevented the development of mitral regurgitation after posterobasal infarction but had no effect on remodeling.ConclusionThe extent of postinfarction remodeling is determined on the basis of infarct size and location. The development of ischemic mitral regurgitation might not contribute significantly to adverse remodeling. Ischemic mitral regurgitation is likely a manifestation rather than an important impetus for postinfarction remodeling
Should mechanical dyssynchrony be assessed in patients with implantable cardioverter-defibrillators?
Cardiac Dysfunction and Arrhythmia
Design and construction of the MicroBooNE Cosmic Ray Tagger system
The MicroBooNE detector utilizes a liquid argon time projection chamber
(LArTPC) with an 85 t active mass to study neutrino interactions along the
Booster Neutrino Beam (BNB) at Fermilab. With a deployment location near ground
level, the detector records many cosmic muon tracks in each beam-related
detector trigger that can be misidentified as signals of interest. To reduce
these cosmogenic backgrounds, we have designed and constructed a TPC-external
Cosmic Ray Tagger (CRT). This sub-system was developed by the Laboratory for
High Energy Physics (LHEP), Albert Einstein center for fundamental physics,
University of Bern. The system utilizes plastic scintillation modules to
provide precise time and position information for TPC-traversing particles.
Successful matching of TPC tracks and CRT data will allow us to reduce
cosmogenic background and better characterize the light collection system and
LArTPC data using cosmic muons. In this paper we describe the design and
installation of the MicroBooNE CRT system and provide an overview of a series
of tests done to verify the proper operation of the system and its components
during installation, commissioning, and physics data-taking
A Deep Neural Network for Pixel-Level Electromagnetic Particle Identification in the MicroBooNE Liquid Argon Time Projection Chamber
We have developed a convolutional neural network (CNN) that can make a
pixel-level prediction of objects in image data recorded by a liquid argon time
projection chamber (LArTPC) for the first time. We describe the network design,
training techniques, and software tools developed to train this network. The
goal of this work is to develop a complete deep neural network based data
reconstruction chain for the MicroBooNE detector. We show the first
demonstration of a network's validity on real LArTPC data using MicroBooNE
collection plane images. The demonstration is performed for stopping muon and a
charged current neutral pion data samples
Measurement of the Z/gamma* + b-jet cross section in pp collisions at 7 TeV
The production of b jets in association with a Z/gamma* boson is studied
using proton-proton collisions delivered by the LHC at a centre-of-mass energy
of 7 TeV and recorded by the CMS detector. The inclusive cross section for
Z/gamma* + b-jet production is measured in a sample corresponding to an
integrated luminosity of 2.2 inverse femtobarns. The Z/gamma* + b-jet cross
section with Z/gamma* to ll (where ll = ee or mu mu) for events with the
invariant mass 60 < M(ll) < 120 GeV, at least one b jet at the hadron level
with pT > 25 GeV and abs(eta) < 2.1, and a separation between the leptons and
the jets of Delta R > 0.5 is found to be 5.84 +/- 0.08 (stat.) +/- 0.72 (syst.)
+(0.25)/-(0.55) (theory) pb. The kinematic properties of the events are also
studied and found to be in agreement with the predictions made by the MadGraph
event generator with the parton shower and the hadronisation performed by
PYTHIA.Comment: Submitted to the Journal of High Energy Physic
Performance of the CMS Cathode Strip Chambers with Cosmic Rays
The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device
in the CMS endcaps. Their performance has been evaluated using data taken
during a cosmic ray run in fall 2008. Measured noise levels are low, with the
number of noisy channels well below 1%. Coordinate resolution was measured for
all types of chambers, and fall in the range 47 microns to 243 microns. The
efficiencies for local charged track triggers, for hit and for segments
reconstruction were measured, and are above 99%. The timing resolution per
layer is approximately 5 ns
ACC/AHA/ASNC Guidelines for the Clinical Use of Cardiac Radionuclide Imaging—Executive Summary: A Report of the American College of Cardiology/American HeartAssociation Task Force on Practice Guidelines (ACC/AHA/ASNC Committee to Revise the 1995 Guidelines for the Clinical Use of Cardiac Radionuclide Imaging)
The American College of Cardiology (ACC)/American Heart Association (AHA) Task Force on Practice Guidelines regularly reviews existing guidelines to determine when an update or full revision is needed. Guidelines for the Clinical Use of Cardiac Radionuclide Imaging were originally published in 1986 and updated in 1995. Important new developments have continued to occur since 1995, particularly in the areas of acute and chronic ischemic syndromes and heart failure. The Task Force therefore believed the topic should be revisited de novo and invited the American Society for Nuclear Cardiology (ASNC) to cosponsor the undertaking, which represents a joint effort of the 3 organizations
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