884 research outputs found

    Flow velocity mapping using contrast enhanced high-frame-rate plane wave ultrasound and image tracking: methods and initial in vitro and in vivo evaluation

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    Ultrasound imaging is the most widely used method for visualising and quantifying blood flow in medical practice, but existing techniques have various limitations in terms of imaging sensitivity, field of view, flow angle dependence, and imaging depth. In this study, we developed an ultrasound imaging velocimetry approach capable of visualising and quantifying dynamic flow, by combining high-frame-rate plane wave ultrasound imaging, microbubble contrast agents, pulse inversion contrast imaging and speckle image tracking algorithms. The system was initially evaluated in vitro on both straight and carotid-mimicking vessels with steady and pulsatile flows and in vivo in the rabbit aorta. Colour and spectral Doppler measurements were also made. Initial flow mapping results were compared with theoretical prediction and reference Doppler measurements and indicate the potential of the new system as a highly sensitive, accurate, angle-independent and full field-of-view velocity mapping tool capable of tracking and quantifying fast and dynamic flows

    Time-Scale Domain Characterization of Time-Varying Ultrawideband Infostation Channel

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    The time-scale domain geometrical-based method for the characterization of the time varying ultrawideband (UWB) channel typical of an infostation channel is presented. Compared to methods that use Doppler shift as a measure of time-variation in the channel this model provides a more reliable measure of frequency dispersion caused by terminal mobility in the UWB infostation channel. Particularly, it offers carrier frequency independent method of computing wideband channel responses and parameters which are important for ultrawideband systems. Results show that the frequency dispersion of the channel depends on the frequency and not on the choice of bandwidth. And time dispersion depends on bandwidth and not on the frequency. It is also shown that for time-varying UWB, frame length defined over the coherence time obtained with reference to the carrier frequency results in an error margin which can be reduced by using the coherence time defined with respect to the maximum frequency in a given frequency band. And the estimation of the frequency offset using the time-scale domain (wideband) model presented here (especially in the case of multiband UWB frequency synchronization) is more accurate than using frequency offset estimate obtained from narrowband models

    Relay beamforming to mitigate inter-relay interference in multi-cell scenario

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    In relay assisted Long Term Evolution-Advanced (LTE-A) network, enhanced Node B (eNB) autonomously selects different backhaul sub-frame configurations to adopt traffic variations, which might cause inter-relay interference (IRI) between relay nodes (RNs) in adjacent cells. IRI can happen due to asynchronous transmission between adjacent cells, which results in IRI from the access link to the backhaul link of adjacent relay in the downlink direction and vice versa. This causes severe loss in system capacity and introduces high outage probability. In this article, we consider the IRI problem in a multi-cell relaying system. Previous studies consider the beamforming design for cooperative relay network as a single-cell problem, without taking into account the occurrence of IRI. However, the performance of the RN assisted network is limited by the IRI from adjacent RN. A hybrid zero-forcing and singular value decomposition (ZF-SVD) beamforming technique is proposed to eliminate the IRI. Simulation results show that the proposed scheme out-performs the comparable scheme in both the ergodic capacity and outage probability

    Muscle Ultrasound Changes and Physical Function of Critically Ill Children: A Comparison of Rectus Femoris Cross-Sectional Area and Quadriceps Thickness Measurements.

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    UNLABELLED: Quadriceps thickness (QT) and rectus femoris cross-sectional area (RFCSA) are both used to evaluate muscle changes in critically ill children. However, their correlation and association with physical function has not been compared. OBJECTIVES: To compare QT with RFCSA changes, and their association with physical function in critically ill children. DESIGN SETTING AND PARTICIPANTS: Secondary analysis of a prospective cohort study of children 0-18 years old admitted to a tertiary mixed PICU between January 2015 and October 2018 with PICU stay greater than 48 hours and greater than or equal to one organ dysfunction. MAIN OUTCOMES AND MEASURES: Ultrasound QT and RFCSA were measured at PICU admission, PICU discharge, hospital discharge, and 6 months post-discharge. QT and RFCSA changes from baseline were compared with each other and with change in motor function, physical ability, and physical health-related quality of life (HRQOL). RESULTS: Two hundred thirty-seven images from 66 subjects were analyzed. RFCSA change was not significantly different from QT change at PICU (-8.07% [interquartile range (IQR), -17.11% to 4.80%] vs -4.55% [IQR, -14.32% to 4.35%]; p = 0.927) or hospital discharge (-5.62% [IQR, -15.00% to 9.42%] vs -8.81% [IQR, -18.67% to 2.39%]; p = 0.238) but was significantly greater than QT change at 6 months (32.7% [IQR, 5.74-109.76%] vs 9.66% [IQR, -8.17% to 25.70%]; p < 0.001). Motor function change at PICU discharge was significantly associated with RFCSA change (adjusted β coefficient, 0.02 [95% CI, 0.01-0.03]; p = 0.013) but not QT change (adjusted β coefficient, -0.01 [95% CI, -0.02 to 0.01]; p = 0.415). Similar results were observed for physical HRQOL changes at hospital discharge (adjusted β coefficient for RFCSA change, 0.51 [95% CI, 0.10-0.92]; p = 0.017 and adjusted β coefficient for QT change, -0.21 [-0.76 to 0.35]; p = 0.458). Physical ability was not significantly associated with RFCSA or QT changes at 6 months post-discharge. CONCLUSIONS AND RELEVANCE: Ultrasound derived RFCSA is associated with PICU motor function and hospital discharge physical HRQOL changes, unlike QT, and may be more useful for in-hospital muscle monitoring in critically ill children

    Robust multiple frequency multiple power localization schemes in the presence of multiple jamming attacks

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    Localization of the wireless sensor network is a vital area acquiring an impressive research concern and called upon to expand more with the rising of its applications. As localization is gaining prominence in wireless sensor network, it is vulnerable to jamming attacks. Jamming attacks disrupt communication opportunity among the sender and receiver and deeply impact the localization process, leading to a huge error of the estimated sensor node position. Therefore, detection and elimination of jamming influence are absolutely indispensable. Range-based techniques especially Received Signal Strength (RSS) is facing severe impact of these attacks. This paper proposes algorithms based on Combination Multiple Frequency Multiple Power Localization (C-MFMPL) and Step Function Multiple Frequency Multiple Power Localization (SF-MFMPL). The algorithms have been tested in the presence of multiple types of jamming attacks including capture and replay, random and constant jammers over a log normal shadow fading propagation model. In order to overcome the impact of random and constant jammers, the proposed method uses two sets of frequencies shared by the implemented anchor nodes to obtain the averaged RSS readings all over the transmitted frequencies successfully. In addition, three stages of filters have been used to cope with the replayed beacons caused by the capture and replay jammers. In this paper the localization performance of the proposed algorithms for the ideal case which is defined by without the existence of the jamming attack are compared with the case of jamming attacks. The main contribution of this paper is to achieve robust localization performance in the presence of multiple jamming attacks under log normal shadow fading environment with a different simulation conditions and scenarios

    Competency-based training in the supervision of relational telemental supervision

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    Supervision has long been considered essential to developing effective mental health practice, especially among COAMFTE accredited training programs. But with telemental health rapidly being accepted as a standard treatment medium for couple and family therapy, there is little guidance about how to supervise clinicians who are engaged in telemental health practice. This paper presents an important step toward increasing the effectiveness of the supervision of therapists who are delivering relational therapies online through the identification of relational competencies unique to this delivery medium. These competencies have been adopted and integrated into a COAMFTE accredited master\u27s degree program that has been providing training in telemental health since 2008. The competencies are described, and supervision strategies that can be utilized and developmentally assessed throughout the program will be detailed

    Using amplify-and-forward relay for coverage extension in indoor environments

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    Cooperative communication is a promising method for increasing the capacity and extending the coverage between a base station (BS) and a mobile user (MU) by using relays to exploit cooperative diversity. However, the existing literature mainly focuses on theoretical performance evaluation without experimental validation and, thus, fails to address the effects on real-world radio signal propagation. This research, therefore, aims to develop a prototype amplify-and-forward (AF) relay using software-defined radio (SDR) to evaluate the real-world performance of such a relay in improving coverage. The proposed relay is developed using the LabVIEW software and programmed on a National Instruments-Universal Software Radio Peripheral 2922 (NI-USRP 2922) SDR platform. The major merit of this entire communication setup is less expensive as the system uses a reprogrammable hardware. The measurements are performed indoors, and the signal strength or received power at the MU in cases with and without the relay is recorded. The results show that the received power performance and signal-to-noise ratio (SNR) at the user improve significantly when the AF relay is deployed compared to when direct link point-to-point transmission without the relay is used

    Evacuation of the Pleural Cavity With an Infant Feeding Catheter Following en Bloc Resection of Hepatocellular Carcinoma and Involved Diaphragm–an Institutional Experience

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    En bloc resection of hepatocellular carcinoma and the involved diaphragm will, towards the end of operation, require evacuation of the pleural cavity, usually with a chest drain. We describe our method and experience of evacuating the pleural cavity, at the time of diaphragmatic repair, with an infant feeding catheter without the need of a chest drain. We have found the method safe and efficacious

    Patient-Specific Prosthetic Fingers by Remote Collaboration - A Case Study

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    The concealment of amputation through prosthesis usage can shield an amputee from social stigma and help improve the emotional healing process especially at the early stages of hand or finger loss. However, the traditional techniques in prosthesis fabrication defy this as the patients need numerous visits to the clinics for measurements, fitting and follow-ups. This paper presents a method for constructing a prosthetic finger through online collaboration with the designer. The main input from the amputee comes from the Computer Tomography (CT) data in the region of the affected and the non-affected fingers. These data are sent over the internet and the prosthesis is constructed using visualization, computer-aided design and manufacturing tools. The finished product is then shipped to the patient. A case study with a single patient having an amputated ring finger at the proximal interphalangeal joint shows that the proposed method has a potential to address the patient's psychosocial concerns and minimize the exposure of the finger loss to the public.Comment: Open Access articl
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