Quantitative Doppler tissue imaging as a correlate of left ventricular contractility

Doppler tissue imaging is a new noninvasive imaging modality that allows quantitation of the low intensity, high amplitude Doppler shifts in the range of myocardial tissue motion. This study was performed to test the hypothesis that Doppler tissue imaging may provide unique information reflecting left ventricular systolic function, and to test the relationship between myocardial tissue velocity and noninvasive measures of ventricular contractility. Nine patients with mild or moderate mitral insufficiency and no regional wall motion abnormality were studied during dobutamine stress echocardiography. Left ventricular ejection fraction and peak systolic velocity of the sub- endocardial left ventricular posterior wall were quantified at baseline and at peak stress and compared with estimated peak dP/dt. During dobutamine infusion, ejection fraction increased from 41.7±22.2 (range 14 to 70) % to 56.6±27.9 (range 17 to 84) % (p=0.001), peak systolic velocity increased from 22.7±4.2 (range 18 to 28) mm/sec to 35.3±10.1 (range 20 to 47) mm/sec (p=0.004), and dP/dt increased from 1050±322 (range 613 to 1574) mm Hg/sec to 1766±768 (range 936 to 3000) mm Hg/sec (p=0.01). Although there were good correlations between left ventricular dP/dt and both ejection fraction (R=0.75) and peak systolic velocity (R=0.81), the correlation between change in dP/dt and change in myocardial velocity (R=0.75) was better than that between change in dP/dt and change in ejection fraction (R=0.36). These data support the hypothesis that myocardial velocity determined with Doppler tissue imaging reflects myocardial contractility, and that catecholamine- induced alteration in contractility is better reflected by changes in myocardial velocity than by changes in ejection fraction.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42539/1/10554_2005_Article_BF01806222.pd

Testing foundations of quantum mechanics with photons

The foundational ideas of quantum mechanics continue to give rise to counterintuitive theories and physical effects that are in conflict with a classical description of Nature. Experiments with light at the single photon level have historically been at the forefront of tests of fundamental quantum theory and new developments in photonics engineering continue to enable new experiments. Here we review recent photonic experiments to test two foundational themes in quantum mechanics: wave-particle duality, central to recent complementarity and delayed-choice experiments; and Bell nonlocality where recent theoretical and technological advances have allowed all controversial loopholes to be separately addressed in different photonics experiments.Comment: 10 pages, 5 figures, published as a Nature Physics Insight review articl

The Scandinavian multicenter hemodynamic evaluation of the SJM Regent aortic valve

Background: 112 patients who received small and medium sized St.Jude Regent heart valves (19-25 mm) at 7 Scandinavian centers were studied between January 2003 and February 2005 to obtain non-invasive data regarding the hemodynamic performance at rest and during Dobutamine stress echocardiography (DSE) testing one year after surgery. Material and methods: 46 woman and 66 men, aged 61.8 +/- 9.7 (18-75) years, were operated on for aortic regurgitation (17), stenosis (65), or mixed dysfunction (30). Valve sizes were 19 mm (6), 21 mm (33), 23 mm (41), 25 mm (30). Two patients receiving size 27 valves were excluded from the hemodynamic evaluation. Pledgets were used in 100 patients, everted mattress in 66 and simple interrupted sutures in 21. Valve orientation varied and was dependent on the surgeons' choice. 34 patients (30.4%) underwent concomitant coronary artery surgery. Results: There were two early deaths (1.8%) and three late deaths, one because of pancreatic cancer. Late events during follow-up were: non structural dysfunction (1), bleeding (2), thromboembolism (2). At one year follow up 93% of the patients were in NYHA classes 1-2 versus 47.8% preoperatively. Dobutamine stress echocardiography (DSE) was performed in a total of 66 and maximal peak stress was reached in 61 patients. During DSE testing, the following statistically significant changes took place: Heart rate increased by 73.0%, cardiac output by 85.5%, left ventriclular ejection fraction by 19.6%, and maximal mean prosthetic transvalvular gradient by 133.8%, whereas the effective orifice area index did not change. Left ventricular mass fell during one year from 215 +/- 63 to 197 +/- 62 g (p < 0.05). Conclusion: The Dobutamine test induces a substantial stress, well suitable for echocardiographic assessment of prosthesis valve function and can be performed in the majority of the patients. The changes in pressure gradients add to the hemodynamic characteristics of the various valve sizes. In our patients the St. Jude Regent valve performed satisfactory at rest and under pharmacological stress situation

Deterministic diffusion fiber tracking improved by quantitative anisotropy

Diffusion MRI tractography has emerged as a useful and popular tool for mapping connections between brain regions. In this study, we examined the performance of quantitative anisotropy (QA) in facilitating deterministic fiber tracking. Two phantom studies were conducted. The first phantom study examined the susceptibility of fractional anisotropy (FA), generalized factional anisotropy (GFA), and QA to various partial volume effects. The second phantom study examined the spatial resolution of the FA-aided, GFA-aided, and QA-aided tractographies. An in vivo study was conducted to track the arcuate fasciculus, and two neurosurgeons blind to the acquisition and analysis settings were invited to identify false tracks. The performance of QA in assisting fiber tracking was compared with FA, GFA, and anatomical information from T 1-weighted images. Our first phantom study showed that QA is less sensitive to the partial volume effects of crossing fibers and free water, suggesting that it is a robust index. The second phantom study showed that the QA-aided tractography has better resolution than the FA-aided and GFA-aided tractography. Our in vivo study further showed that the QA-aided tractography outperforms the FA-aided, GFA-aided, and anatomy-aided tractographies. In the shell scheme (HARDI), the FA-aided, GFA-aided, and anatomy-aided tractographies have 30.7%, 32.6%, and 24.45% of the false tracks, respectively, while the QA-aided tractography has 16.2%. In the grid scheme (DSI), the FA-aided, GFA-aided, and anatomy-aided tractographies have 12.3%, 9.0%, and 10.93% of the false tracks, respectively, while the QA-aided tractography has 4.43%. The QA-aided deterministic fiber tracking may assist fiber tracking studies and facilitate the advancement of human connectomics. © 2013 Yeh et al

The Time Course of Segmentation and Cue-Selectivity in the Human Visual Cortex

Texture discontinuities are a fundamental cue by which the visual system segments objects from their background. The neural mechanisms supporting texture-based segmentation are therefore critical to visual perception and cognition. In the present experiment we employ an EEG source-imaging approach in order to study the time course of texture-based segmentation in the human brain. Visual Evoked Potentials were recorded to four types of stimuli in which periodic temporal modulation of a central 3° figure region could either support figure-ground segmentation, or have identical local texture modulations but not produce changes in global image segmentation. The image discontinuities were defined either by orientation or phase differences across image regions. Evoked responses to these four stimuli were analyzed both at the scalp and on the cortical surface in retinotopic and functional regions-of-interest (ROIs) defined separately using fMRI on a subject-by-subject basis. Texture segmentation (tsVEP: segmenting versus non-segmenting) and cue-specific (csVEP: orientation versus phase) responses exhibited distinctive patterns of activity. Alternations between uniform and segmented images produced highly asymmetric responses that were larger after transitions from the uniform to the segmented state. Texture modulations that signaled the appearance of a figure evoked a pattern of increased activity starting at ∼143 ms that was larger in V1 and LOC ROIs, relative to identical modulations that didn't signal figure-ground segmentation. This segmentation-related activity occurred after an initial response phase that did not depend on the global segmentation structure of the image. The two cue types evoked similar tsVEPs up to 230 ms when they differed in the V4 and LOC ROIs. The evolution of the response proceeded largely in the feed-forward direction, with only weak evidence for feedback-related activity

Safety of percutaneous aortic valve insertion. A systematic review

<p>Abstract</p> <p>Background</p> <p>The technique of percutaneous aortic valve implantation (PAVI) for the treatment of severe aortic stenosis (AS) has been introduced in 2002. Since then, many thousands such devices have worldwide been implanted in patients at high risk for conventional surgery. The procedure related mortality associated with PAVI as reported in published case series is substantial, although the intervention has never been formally compared with standard surgery. The objective of this study was to assess the safety of PAVI, and to compare it with published data reporting the risk associated with conventional aortic valve replacement in high-risk subjects.</p> <p>Methods</p> <p>Studies published in peer reviewed journals and presented at international meetings were searched in major medical databases. Further data were obtained from dedicated websites and through contacts with manufacturers. The following data were extracted: patient characteristics, success rate of valve insertion, operative risk status, early and late all-cause mortality.</p> <p>Results</p> <p>The first PAVI has been performed in 2002. Because of procedural complexity, the original transvenous approach from 2004 on has been replaced by the transarterial and transapical routes. Data originating from nearly 2700 non-transvenous PAVIs were identified. In order to reduce the impact of technical refinements and the procedural learning curve, procedure related safety data from series starting recruitment in April 2007 or later (n = 1975) were focused on. One-month mortality rates range from 6.4 to 7.4% in transfemoral (TF) and 11.6 to 18.6% in transapical (TA) series. Observational data from surgical series in patients with a comparable predicted operative risk, indicate mortality rates that are similar to those in TF PAVI but substantially lower than in TA PAVI. From all identified PAVI series, 6-month mortality rates, reflecting both procedural risk and mortality related to underlying co-morbidities, range from 10.0-25.0% in TF and 26.1-42.8% in TA series. It is not known what the survival of these patients would have been, had they been treated medically or by conventional surgery.</p> <p>Conclusion</p> <p>Safety issues and short-term survival represent a major drawback for the implementation of PAVI, especially for the TA approach. Results from an ongoing randomised controlled trial (RCT) should be awaited before further using this technique in routine clinical practice. In the meantime, both for safety concerns and for ethical reasons, patients should only be subjected to PAVI within the boundaries of such an RCT.</p

Effective Rheology of Bubbles Moving in a Capillary Tube

We calculate the average volumetric flux versus pressure drop of bubbles moving in a single capillary tube with varying diameter, finding a square-root relation from mapping the flow equations onto that of a driven overdamped pendulum. The calculation is based on a derivation of the equation of motion of a bubble train from considering the capillary forces and the entropy production associated with the viscous flow. We also calculate the configurational probability of the positions of the bubbles.Comment: 4 pages, 1 figur

Jet energy measurement with the ATLAS detector in proton-proton collisions at root s=7 TeV

The jet energy scale and its systematic uncertainty are determined for jets measured with the ATLAS detector at the LHC in proton-proton collision data at a centre-of-mass energy of √s = 7TeV corresponding to an integrated luminosity of 38 pb-1. Jets are reconstructed with the anti-kt algorithm with distance parameters R=0. 4 or R=0. 6. Jet energy and angle corrections are determined from Monte Carlo simulations to calibrate jets with transverse momenta pT≥20 GeV and pseudorapidities {pipe}η{pipe}<4. 5. The jet energy systematic uncertainty is estimated using the single isolated hadron response measured in situ and in test-beams, exploiting the transverse momentum balance between central and forward jets in events with dijet topologies and studying systematic variations in Monte Carlo simulations. The jet energy uncertainty is less than 2. 5 % in the central calorimeter region ({pipe}η{pipe}<0. 8) for jets with 60≤pT<800 GeV, and is maximally 14 % for pT<30 GeV in the most forward region 3. 2≤{pipe}η{pipe}<4. 5. The jet energy is validated for jet transverse momenta up to 1 TeV to the level of a few percent using several in situ techniques by comparing a well-known reference such as the recoiling photon pT, the sum of the transverse momenta of tracks associated to the jet, or a system of low-pT jets recoiling against a high-pT jet. More sophisticated jet calibration schemes are presented based on calorimeter cell energy density weighting or hadronic properties of jets, aiming for an improved jet energy resolution and a reduced flavour dependence of the jet response. The systematic uncertainty of the jet energy determined from a combination of in situ techniques is consistent with the one derived from single hadron response measurements over a wide kinematic range. The nominal corrections and uncertainties are derived for isolated jets in an inclusive sample of high-pT jets. Special cases such as event topologies with close-by jets, or selections of samples with an enhanced content of jets originating from light quarks, heavy quarks or gluons are also discussed and the corresponding uncertainties are determined. © 2013 CERN for the benefit of the ATLAS collaboration