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Electrical wave-front propagation in the atria is determined largely by local fiber orientation. Recent study suggests that atrial fibrillation (AF) progresses with enhanced anisotropy. In this work, a 3D rabbit atrial anatomical model at 20×20×20 µm3 resolution with realistic fiber orientation was constructed based on the novel contrast-enhanced micro-CT imaging. The Fenton-Karma cellular activation...
Changes in P wave duration (PWD) following atrial fibrillation (AF) ablation have been described and may have diagnostic value. PWD is usually assessed manually from ECG. This study aimed at exploring a novel method for automated modeling of the P-wave and assessment of PWD. Moreover, it aimed at investigating the effect of hybrid procedure (HP) for AF treatment on PWD. P-wave modeling is achieved...
Spiral wave drifting and meandering are known measures for cardiac instability and arrhythmogenesis. This study was aimed to analyze spiral wave drifting due to temperature heterogeneity that is applied artificially. Our hypothesis is that spatial temperature gradients (STGs) will cause spatial excitability heterogeneity, which in turn will affect the spiral waves' dynamics. This may help to detect,...
The accurate carotid plaques segmentation (CPs-S) is essential in the ultrasound (US)-guided carotid atherosclerosis diagnosis. In this work, we propose CAPSU: a completely automated method for CPs-S in US images. The core of the method is an innovative initialization procedure that exploits carotid wall motion analysis to automatically initialize a level-set segmentation algorithm. A strain analysis...
Parameters derived from the pulse photoplethysmographic (PPG) signal, such as pulse rate, amplitude, and width variability (PRV, PAV and PWV) have been previously proposed for deriving respiratory rate, obtaining less accurate estimates for higher respiratory rates (0.5–0.6 Hz). In this work we analyze the power of respiration related oscillations in PRV, PAV and PWV as a function of respiratory rate...
The aim of this study was to evaluate changes in AV nodal properties during administration of metoprolol, using a novel ECG-based method for parameter estimation. The AV nodal parameters account for the probability of an impulse not passing through the fast pathway, the absolute refractory periods of the slow and fast pathways (aRPs and aRPf), representing the functional refractory period, and related...
Current approaches to classification of left ventricular scar rely on manual segmentation of myocardial borders and manual classification of scar tissue. In this paper, we propose an novel, semi-automatic approach to segment the left ventricular wall and classify scar tissue using a combination of modern image processing techniques. We obtained high-resolution magnetic resonance angiograms (MRA) and...
Systole and diastole are the fundamental periods of the cardiac cycle and their relative duration is used to evaluate heart function in various physiological and pathological conditions. In clinical practice, systolic-diastolic interval is generally measured using echocardiography. However, recent studies have shown that the QT and TQ intervals of the electrocardiogram (ECG) signal can be used as...
The underlying mechanisms that lead to syncope are still unclear, especially in children. In this work, we applied a novel point-process model to study time-varying heartbeat dynamics and to characterize autonomic changes that occur prior to a syncopal event. Twenty-six children with history compatible with neurocardiogenic syncope (NCS) and a positive head up tilt table test (HUT) were included in...
Introduction. Previously, we demonstrated that certain patterns of abnormal rapid beats, notably “short-long-short-short” (SLSS) patterns, tend to produce action potential block in computer models, and tend to initiate VF in in vivo canine experiments, consistent with our theory based on electrical restitution. Here we present evidence that these same patterns often precede VF in human ECG recordings...
We provide an analysis of the bidomain theory in relation to anterior subendocardial ischemia. Using the static bidomain model, this analysis explains why simulations often do not produce ST depression when the ischemia is introduced into an anisotropic model. More precisely, if the ischemic border zone is represented as a smooth surface, then almost right angles between the normal vector of the border...
Cardiac electrical imaging often requires the examination of different forward and inverse problem formulations based on mathematical and numerical approximations of the underlying source and the intervening volume conductor that can generate the associated voltages on the surface of the body. If the goal is to recover the source on the heart from body surface potentials, the solution strategy must...
A new multi-modal biometric authentication approach using gait and electrocardiogram (ECG) signals as biometric traits is proposed. The individual comparison scores derived from the gait and ECG are normalized using several methods (min-max, z-score, median absolute deviation, tangent hyperbolic) and then four fusion approaches (simple sum, user-weighting, maximum score and minimum core) are applied...
Common image features have too poor information for identification of forensic images of fingerprints, where only a small area of the finger is imaged and hence a small amount of key points are available. Noise, nonlinear deformation, and unknown rotation are additional issues that complicate identification of forensic fingerprints. We propose a feature extraction method which describes image information...
New model-reduction numerical procedure for a class of stable nonlinear systems is proposed. The proposed design is devoted to a spacial class of nonlinear systems whose nonlinearities are not necessarily Lipschitz with respect to its arguments. Additionally, the systems under consideration may contain uncertain parameters, having known lower and upper bounds. The computation of the reduced-model...
The introduction of IPv6 has opened up several questions with reference to its adaption and transition from IPv4 to IPv6 and is one of the crucial issues being frequently discussed in networking community today. IPv6 provides many seamless features that makes it far better protocol as compared to its predecessor IPv4. It is a well-known fact that IPv4 is a defacto standard at present and is currently...
Locks have been widely used as an effective synchronization mechanism among processes and threads. However, we observe that a large number of false inter-thread dependencies (i.e., unnecessary lock contentions) exist during the program execution on multicore processors, thereby incurring significant performance overhead. This paper presents a performance debugging framework, PerfPlay, to facilitate...
A practical shadowing test technique for the trimmed NURBS surface (TNS) is presented in this work. By employing an efficient Bezier patch classification algorithm, a two-level hierarchical space partitioning volume (HSPV) is built for the TNS, where the leaves of the HSPV that contains trimmed off part of the original surface are marked out, making sure the shadowing test occurs on the effective...
This work proposes a system for the analysis and the comparison of users profiles in social networks. Posts are extracted and analyzed in order to detect similar contents, like topics, sentiments and writing styles. A case study regarding the analysis of the authenticity of profiles of the Italian prime minister in different social networks is illustrated.
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