Securities Regulation: Shareholder Derivative Actions Against Insiders Under Rule 10b-5

After a general examination of Rule 10b-5 in the context of its traditional application, this comment focuses on the recent developments concerning the rule\u27s function as a weapon for the enforcement of controlling insiders\u27 duties to their corporation

Three-dimensional myocardial strain estimation from volumetric ultrasound: experimental validation in an animal model

Although real-time three-dimensional echocardiography has the potential to allow for more accurate assessment of global and regional ventricular dynamics compared to the more traditional two-dimensional ultrasound examinations, it still requires rigorous testing and validation against other accepted techniques should it breakthrough as a standard examination in routine clinical practice. Very few studies have looked at a validation of regional functional indices in an in-vivo context. The aim of the present study therefore was to validate a previously proposed 3D strain estimation-method based on elastic registration of subsequent volumes on a segmental level in an animal model. Volumetric images were acquired with a GE Vivid7 ultrasound system in five open-chest sheep instrumented with ultrasonic microcrystals. Radial (epsilon(RR)), longitudinal (epsilon(LL)) and circumferential strain (epsilon(CC)) were estimated during four stages: at rest, during esmolol and dobutamine infusion, and during acute ischemia. Moderate correlations for epsilon(LL) (r=0.63; p<0.01) and epsilon(CC) (r=0.60; p=0.01) were obtained, whereas no significant radial correlation was found. These findings are comparable to the performance of the current state-of-the-art commercial 3D speckle tracking methods

Fully automatic left ventricular myocardial strain estimation in 2D short-axis tagged magnetic resonance imaging

Cardiovascular diseases are among the leading causes of death and frequently result in local myocardial dysfunction. Among the numerous imaging modalities available to detect these dysfunctional regions, cardiac deformation imaging through tagged magnetic resonance imaging (t-MRI) has been an attractive approach. Nevertheless, fully automatic analysis of these data sets is still challenging. In this work, we present a fully automatic framework to estimate left ventricular myocardial deformation from t-MRI. This strategy performs automatic myocardial segmentation based on B-spline explicit active surfaces, which are initialized using an annular model. A non-rigid image-registration technique is then used to assess myocardial deformation. Three experiments were set up to validate the proposed framework using a clinical database of 75 patients. First, automatic segmentation accuracy was evaluated by comparing against manual delineations at one specific cardiac phase. The proposed solution showed an average perpendicular distance error of 2.35 +/- 1.21 mm and 2.27 +/- 1.02 mm for the endo- and epicardium, respectively. Second, starting from either manual or automatic segmentation, myocardial tracking was performed and the resulting strain curves were compared. It is shown that the automatic segmentation adds negligible differences during the strain-estimation stage, corroborating its accuracy. Finally, segmental strain was compared with scar tissue extent determined by delay-enhanced MRI. The results proved that both strain components were able to distinguish between normal and infarct regions. Overall, the proposed framework was shown to be accurate, robust, and attractive for clinical practice, as it overcomes several limitations of a manual analysis.FCT—Fundacão para a Ciência e a Tecnologia, Portugal, and the European Social Found, European Union, for funding support through the Programa Operacional Capital Humano (POCH) in the scope of the PhD grants SFRH/BD/95438/2013 (P Morais) and SFRH/BD/93443/2013 (S Queirós). This work was supported by the projects NORTE-07-0124-FEDER-000017 and NORTE-01-0145-FEDER-000013, co-funded by Programa Operacional Regional do Norte, Quadro de Referência Estratégico Nacional, through Fundo Europeu de Desenvolvimento Regional (FEDER). The authors would also like to acknowledge the EU (FP7) framework program, for the financial support of the DOPPLER-CIP project (grant no. 223615)info:eu-repo/semantics/publishedVersio

Elastic image registration versus speckle tracking for 2-D myocardial motion estimation: a direct comparison in vivo

Despite the availability of multiple solutions for assessing myocardial strain by ultrasound, little is currently known about the relative performance of the different methods. In this study, we sought to contrast two strain estimation techniques directly (speckle tracking and elastic registration) in an in vivo setting by comparing both to a gold standard reference measurement. In five open-chest sheep instrumented with ultrasonic microcrystals, 2-D images were acquired with a GE Vivid7 ultrasound system. Radial (epsilon(RR)) , longitudinal (epsilon(LL)) , and circumferential strain (epsilon(CC)) were estimated during four inotropic stages: at rest, during esmolol and dobutamine infusion, and during acute ischemia. The correlation of the end-systolic strain values of a well-validated speckle tracking approach and an elastic registration method against sonomicrometry were comparable for epsilon(LL) (r = 0.70 versus r = 0.61, respectively; p = 0.32) and epsilon(CC) (r = 0.73 versus r = 0.80 respectively; p = 0.31). However, the elastic registration method performed considerably better for epsilon(RR) (r = 0.64 versus r = 0.85 respectively; p = 0.09). Moreover, the bias and limits of agreement with respect to the reference strain estimates were statistically significantly smaller in this direction (p < 0.001). This could be related to regularization which is imposed during the motion estimation process as opposed to an a posteriori regularization step in the speckle tracking method. Whether one method outperforms the other in detecting dysfunctional regions remains the topic of future research

Non-Rigid Image Registration for the Assessment of Myocardial Deformation from 3D Echocardiography (Niet-rigide beeldregistratie voor het bepalen van de hartspiervervorming met behulp van 3D ultrasone beelden)

Cardiovascular diseases are currently the major cause of death in the wo rld. Cardiac imaging therefore plays an essential role in the diagnosis, management and follow-up of patients with any suspected or known cardio vascular disease. Ultrasound (US) imaging is a well established imaging modality in daily clinical practice for the evaluation of cardiac morpho logy and function by measuring cardiac wall motion and deformation (i.e. strain). Several recent technological advancements have made a real-tim e assessment of the heart in three dimensions now possible, and thus off er the possibility to improve and expand on the diagnostic capabilities of the traditional two-dimensional (2D) US images. Analyzing these datas ets however is a challenging endeavor as the spatial and temporal resolu tion is currently lower than in 2D and the large amount of data makes a manual evaluation cumbersome and subjective. The focus of the present thesis was therefore the development of non-rig id image registration techniques able to cope with these demanding condi tions. We illustrate that image registration is a viable technique for r egional cardiac function estimation by validating the technique in a var iety of cardiac ultrasound imaging scenarios. An in-vitro experimental s etup was built in which tissue-mimicking phantoms could be deformed and imaged. Some phantoms contained stiff inclusions to investigate to what extent dysfunctional areas could be identified. An in-vivo animal study was also designed to acquire volumetric data in 17 open-chest sheep subj ect to conditions comparable to those encountered in clinical situations such as ischemia. New regularisation methods were proposed to improve cardiac deformation estimates. A strategy was derived to adapt the topology of the control p oint grid of the non-rigid image registration method to the anatomy of t he heart. It was shown that such a model is more suited for cardiac def ormation. Efforts were made to automate the strain estimation workflow t o facilitate its introduction in clinical practice. Finally, excellent r esults were obtained at an international challenge where the performance of the proposed method was compared against the most competitive algori thms currently available.status: publishe

Current state of 3D myocardial strain estimation using echocardiography

With the developments in ultrasound transducer technology and both hardware and software computing, real-time volumetric imaging has become widely available, accompanied by various methods of assessing three-dimensional (3D) myocardial strain, often referred to as 3D speckle-tracking echocardiographic methods. Indeed, these methods should provide cardiologists with a better view of regional myocardial mechanics, which might be important for diagnosis, prognosis, and therapy. However, currently available 3D speckle-tracking echocardiographic methods are based on different algorithms, which introduce substantial differences between them and make them not interchangeable with each other. Therefore, it is critical that each 3D speckle-tracking echocardiographic method is validated individually before being introduced into clinical practice. In this review, the authors discuss differences and similarities of the currently available 3D strain estimation approaches and provide an overview of the current status of their validation.status: publishe

RF-based motion estimation using non-rigid image registration techniques: in-silico and in-vivo feasibility

US deformation techniques can roughly be divided in block matching (BM) and non-rigid image registration (NRIR). Motion can be extracted from the radio-frequency (RF) signals, from their envelope, or from the B-mode data. RF-based BM is known to outperform B-mode tracking in a small displacement setting, whereas NRIR has only been applied to B-mode data. The aim of this study was to test the feasibility of RF-based NRIR in-silico and in-vivo. First, synthetic 2D images of a phantom with a soft inclusion undergoing an axial compression (0.25%) were simulated. Its performance was assessed by varying the inclusion thickness (range: 2–20 mm in 2 mm steps) and stiffness (resulting strain range: 0.50%–1.50% in 0.25% steps). Both RF and envelope tracking were better at identifying smaller and more subtle inclusions compared to B-mode tracking (down to 8 mm and 6 mm resp.). Furthermore, when tracking the RF instead of their envelope, inclusion borders were more sharply defined (border size 2.57 mm vs 4.88 mm, p<0.001) and strain errors in the inclusion were lower (0.08% vs 0.10%; p<0.05). Next, NRIR was used to track the septum of a healthy volunteer from high frame rate US recordings (436 Hz), and compared against a recent RF-based BM method. In-vivo trackingrevealed that RF-based BM and RF-based NRIR performed similarly, both producing physiological axial velocity and strain curves. The lateral components could only be estimated using NRIR.status: publishe

Impact of beamforming strategies and regularisation on ultrasound displacement estimation using RF-based image registration

© 2017 IEEE. In the context of ultrasound (US) deformation imaging it has been shown that lateral motion estimation can be improved by simultaneously combining transverse oscillation (TO) beamforming with dedicated motion estimators and regularisation techniques. This paper provides insights into the relative contributions of beamforming strategies (focused imaging [FOC], plane wave TO beamforming [PWTO], and PWTO after heterodyning [PWTO∗]) and regularisation (unregularised RF tracking, combined envelope/RF tracking without regularisation, and combined envelope/RF tracking with explicit regularisation) to the performance of US displacement estimation algorithms. More specifically, a non-rigid image registration technique was used to track lateral tissue motion in an in-silico and in-vitro phantom setup for all beamforming-tracking combinations. It was found that PWTO and PWTO∗ tracking benefited more from regularisation than FOC tracking, and was even a necessary requirement to warrant the use of TO beamforming over traditional FOC imaging. For example, for a range of lateral displacements (0-1000 μm), in-silico errors were 56±56 μm and 118±293 μm for the unregularized FOC and PWTO∗ scenario respectively. After regularisation, these errors remained relatively stable for the FOC case but drastically reduced for the PWTO∗ scenario: 51±45 μm versus 14±12 μm respectively.status: publishe