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https://www.readbyqxmd.com/read/29100988/fast-b1-mapping-using-three-consecutive-rf-pulses-and-balanced-gradients-for-improved-bssfp-imaging
#1
Min-Oh Kim, Taehwa Hong, Dong-Hyun Kim
PURPOSE: To develop a B1(+) mapping during the transient phase of balanced steady state free precession (bSSFP) imaging which can be used for subsequent B1(+) inhomogeneity compensation. METHODS: Two images with different flip angles (FA) are acquired using single-shot spiral technique during the transient phase of bSSFP with three consecutive RF pulses and balanced gradients. Under the assumptions that the transmit (B1(+)) field varies slowly in spatial domain and T1 and T2 relaxation effects are negligible during 2·TR, B1(+) was estimated using the two magnitude images and bSSFP data was sequentially acquired...
October 31, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29092484/interferometric-method-for-quantitatively-testing-the-radoptic-effect-in-bulk-semiconductors
#2
Bo-Dong Peng, Yan Song, Dong-Wei Hei, Jun Zhao
For the quantitative investigation of MeV-photon-induced changes in the refractive indices of bulk semiconductors, a model was established to describe the evolution of the excess carrier density, including the generation and recombination processes. The two key parameters of the evolution model, namely, the summed injection intensity and the gamma intensity curve, were obtained via dose measurements and gamma pulse monitoring, respectively. An interferometric method of measuring instantaneous changes in the refractive index and obtaining real-time measurements of the excess carrier density in bulk materials was successfully implemented...
October 2017: Review of Scientific Instruments
https://www.readbyqxmd.com/read/29082751/temporal-and-spatial-distribution-of-isotopes-in-river-water-in-central-europe-50-years-experience-with-the-austrian-network-of-isotopes-in-rivers
#3
Dieter Rank, Stefan Wyhlidal, Katharina Schott, Silvia Weigand, Armin Oblin
The Austrian network of isotopes in rivers comprises about 15 sampling locations and has been operated since 1976. The Danube isotope time series goes back to 1963. The isotopic composition of river water in Central Europe is mainly governed by the isotopic composition of precipitation in the catchment area; evaporation effects play only a minor role. Short-term and long-term isotope signals in precipitation are thus transmitted through the whole catchment. The influence of climatic changes has become observable in the long-term stable isotope time series of precipitation and surface waters...
October 28, 2017: Isotopes in Environmental and Health Studies
https://www.readbyqxmd.com/read/29060063/a-miniaturized-uwb-antenna-for-implantable-data-telemetry
#4
Michael Haas, Benedikt Schweizer, Jens Anders, Maurits Ortmanns
This paper presents a miniaturized impulse radio ultra-wideband (IR-UWB) antenna which is designed for transcutaneous, short-distance data communication used in multichannel neural recording. In these systems, with the increasing number of recording channels, data rates of 10-100 Mbit/s must be transmitted with very limited power and area. Therefore, the antennas are designed as planar, ellipsoidal dipoles on a high permittivity substrate with εr = 10.2 to achieve high radiation efficiency with small physical size...
July 2017: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28991738/focus-fourier-based-coded-ultrasound
#5
Almog Lahav, Tanya Chernyakova, Yonina C Eldar
Modern imaging systems typically use single-carrier short pulses for transducer excitation. Coded signals together with pulse compression are successfully used in radar and communication to increase the amount of transmitted energy. Previous research verified significant improvement in signal-tonoise ratio (SNR) and imaging depth for ultrasound imaging with coded signals. Since pulse compression needs to be applied at each transducer element, the implementation of coded excitation (CE) in array imaging is computationally complex...
October 6, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28964085/short-pulse-method-for-acoustic-backscatter-amplitude-calibration-at-mhz-frequencies
#6
Gregory W Wilson, Alex E Hay
The short-pulse acoustic backscatter amplitude calibration technique of Dragonette, Numrich, and Frank [(1981), J. Acoust. Soc. Am. 69, 1186-1189] is evaluated for MHz frequency systems, as are used to measure environmental suspended sediment concentration. The technique involves measuring backscatter from a short transmit pulse reflected by a solid spherical target, and treating the first received reflection as equivalent to that from a perfectly rigid sphere. In this implementation, the target sphere is 16 mm diameter tungsten carbide...
September 2017: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/28951590/terahertz-spectroscopy-of-anisotropic-materials-using-beams-with-rotatable-polarization
#7
C D W Mosley, M Failla, D Prabhakaran, J Lloyd-Hughes
We introduce a polarization-resolved terahertz time-domain spectrometer with a broadband (0.3-2.5 THz), rotatable THz polarization state, and which exhibits minimal change in the electric field amplitude and polarization state upon rotation. This was achieved by rotating an interdigitated photoconductive emitter, and by detecting the orthogonal components of the generated THz pulse via electro-optic sampling. The high precision (<0.1°) and accuracy (<1.0°) of this approach is beneficial for the study of anisotropic materials without rotating the sample, which can be impractical, for instance for samples held in a cryostat...
September 26, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28946601/efficacy-analysis-of-ldpc-coded-apsk-modulated-differential-space-time-frequency-coded-for-wireless-body-area-network-using-mb-pulsed-ofdm-uwb-technology
#8
C T Manimegalai, Sabitha Gauni, K Kalimuthu
Wireless body area network (WBAN) is a breakthrough technology in healthcare areas such as hospital and telemedicine. The human body has a complex mixture of different tissues. It is expected that the nature of propagation of electromagnetic signals is distinct in each of these tissues. This forms the base for the WBAN, which is different from other environments. In this paper, the knowledge of Ultra Wide Band (UWB) channel is explored in the WBAN (IEEE 802.15.6) system. The measurements of parameters in frequency range from 3...
September 8, 2017: Technology and Health Care: Official Journal of the European Society for Engineering and Medicine
https://www.readbyqxmd.com/read/28880172/spectrum-compensation-for-time-reversal-method-on-ultrasonic-target-detection-using-pulse-compression
#9
Dai Chimura, Ryo Toh, Seiichi Motooka
This paper discusses a method of time reversal (TR) for target detection using a signal with a higher signal-to-noise ratio (SNR) and higher resolution. To acquire a signal with a higher SNR and broader spectrum, we have proposed a sensitivity-compensated (SC) signal. In this study, we propose three types of sensitivity-compensated-for-time-reversal (SC-for-TR) signals. A sensitivity-compensated-amplitude-modulated-for-time-reversal signal and a sensitivity-compensated-frequency-modulated-for-time-reversal signal are calculated using squared spectrum compensation...
September 4, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28866489/simultaneous-ultrasonic-measurement-of-thickness-and-speed-of-sound-in-elastic-plates-using-coded-excitation-signals
#10
Daniel A Kiefer, Michael Fink, Stefan J Rupitsch
Layer thickness and speed of sound are important parameters for non-destructive testing applications. If one of the parameters is known, the other one can be determined by simple time-of-flight measurement of ultrasound. However, often these parameters are both unknown. In this contribution, we examine and adapt ultrasonic imaging techniques using coded excitation signals to simultaneously measure the thickness and speed of sound in homogeneous elastic plates of unknown material. Good axial resolution is required to measure thin samples...
August 30, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28863621/rigid-and-elastic-acoustic-scattering-signal-separation-for-underwater-target
#11
Hongjian Jia, Xiukun Li, Xiangxia Meng
Underwater target elastic acoustic scattering and other acoustic scattering components are aliasing together in the time and frequency domains, and the existing signal processing methods cannot recognize the elastic scattering features under the aliasing condition because of the resolution limitation. To address this problem, this study, which is based on the target echo highlight model, analyzes the characteristics of target acoustic scattering components when the transmitted signal is a linear frequency modulation pulse...
August 2017: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/28829301/stimulation-efficiency-with-decaying-exponential-waveforms-in-a-wirelessly-powered-switched-capacitor-discharge-stimulation-system
#12
Hyung-Min Lee, Bryan Howell, Warren M Grill, Maysam Ghovanloo
The purpose of this study was to test the feasibility of using a switched-capacitor discharge stimulation (SCDS) system for electrical stimulation and subsequently determine the overall energy saved compared to a conventional stimulator. We have constructed a computational model by pairing an image-based volume conductor model of the cat head with cable models of corticospinal tract (CST) axons and quantified the theoretical stimulation efficiency of rectangular and decaying exponential waveforms, produced by conventional and SCDS systems, respectively...
August 17, 2017: IEEE Transactions on Bio-medical Engineering
https://www.readbyqxmd.com/read/28799090/prostate-cancer-detection-among-readers-with-different-degree-of-experience-using-ultra-high-b-value-diffusion-weighted-imaging-is-a-non-contrast-protocol-sufficient-to-detect-significant-cancer
#13
D Hausmann, N Aksöz, J von Hardenberg, T Martini, N Westhoff, S Buettner, S O Schoenberg, P Riffel
AIM: To evaluate the accuracy of a T2-weighted (T2w) - and a parallel transmit zoomed b = 2000 s/mm2 (b2000) - diffusion-weighted imaging sequence among three readers with different degrees of experience for prostate cancer (Pca) detection. METHODS: Ninety-three patients with suspected Pca were enrolled. For b2000 a two-dimensional spatially-selective RF pulse using an echo-planar transmit trajectory was applied, and the field of view (FOV) was reduced to one-third...
August 10, 2017: European Radiology
https://www.readbyqxmd.com/read/28764415/sparse-dictionary-for-synthetic-transmit-aperture-medical-ultrasound-imaging
#14
Ping Wang, Jin-Yang Jiang, Na Li, Han-Wu Luo, Fang Li, Shi-Gang Cui
It is possible to recover a signal below the Nyquist sampling limit using a compressive sensing technique in ultrasound imaging. However, the reconstruction enabled by common sparse transform approaches does not achieve satisfactory results. Considering the ultrasound echo signal's features of attenuation, repetition, and superposition, a sparse dictionary with the emission pulse signal is proposed. Sparse coefficients in the proposed dictionary have high sparsity. Images reconstructed with this dictionary were compared with those obtained with the three other common transforms, namely, discrete Fourier transform, discrete cosine transform, and discrete wavelet transform...
July 2017: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/28672798/a-real-time-contactless-pulse-rate-and-motion-status-monitoring-system-based-on-complexion-tracking
#15
Yu-Chen Lin, Nai-Kuan Chou, Guan-You Lin, Meng-Han Li, Yuan-Hsiang Lin
Subject movement and a dark environment will increase the difficulty of image-based contactless pulse rate detection. In this paper, we detected the subject's motion status based on complexion tracking and proposed a motion index (MI) to filter motion artifacts in order to increase pulse rate measurement accuracy. Additionally, we integrated the near infrared (NIR) LEDs with the adopted sensor and proposed an effective method to measure the pulse rate in a dark environment. To achieve real-time data processing, the proposed framework is constructed on a Field Programmable Gate Array (FPGA) platform...
June 24, 2017: Sensors
https://www.readbyqxmd.com/read/28652642/optical-fiber-ultrasound-transmitter-with-electrospun-carbon-nanotube-polymer-composite
#16
Radhika K Poduval, Sacha Noimark, Richard J Colchester, Thomas J Macdonald, Ivan P Parkin, Adrien E Desjardins, Ioannis Papakonstantinou
All-optical ultrasound transducers are promising for imaging applications in minimally invasive surgery. In these devices, ultrasound is transmitted and received through laser modulation, and they can be readily miniaturized using optical fibers for light delivery. Here, we report optical ultrasound transmitters fabricated by electrospinning an absorbing polymer composite directly onto the end-face of optical fibers. The composite coating consisting of an aqueous dispersion of multi-walled carbon nanotubes (MWCNTs) in polyvinyl alcohol was directly electrospun onto the cleaved surface of a multimode optical fiber and subsequently dip-coated with polydimethylsiloxane (PDMS)...
May 29, 2017: Applied Physics Letters
https://www.readbyqxmd.com/read/28639263/subthalamic-beta-dynamics-mirror-parkinsonian-bradykinesia-months-after-neurostimulator-implantation
#17
Leon Amadeus Steiner, Wolf-Julian Neumann, Franziska Staub-Bartelt, Damian M Herz, Huiling Tan, Alek Pogosyan, Andrea A Kuhn, Peter Brown
BACKGROUND: Exaggerated oscillatory activity in the beta frequency band in the subthalamic nucleus has been suggested to be related to bradykinesia in Parkinson's disease (PD). However, studies seeking correlations between such activity in the local field potential and motor performance have been limited to the immediate postoperative period, which may be confounded by a stun effect that leads to the temporary alleviation of PD deficits. METHODS: Local field potentials were recorded simultaneously with motor performance in PD patients several months after neurostimulator implantation...
August 2017: Movement Disorders: Official Journal of the Movement Disorder Society
https://www.readbyqxmd.com/read/28627331/dynamic-transmit-receive-beamforming-by-spatial-matched-filtering-for-ultrasound-imaging-with-plane-wave-transmission
#18
Yuling Chen, Yang Lou, Jesse Yen
During conventional ultrasound imaging, the need for multiple transmissions for one image and the time of flight for a desired imaging depth limit the frame rate of the system. Using a single plane wave pulse during each transmission followed by parallel receive processing allows for high frame rate imaging. However, image quality is degraded because of the lack of transmit focusing. Beamforming by spatial matched filtering (SMF) is a promising method which focuses ultrasonic energy using spatial filters constructed from the transmit-receive impulse response of the system...
July 2017: Ultrasonic Imaging
https://www.readbyqxmd.com/read/28618605/measurements-of-ionization-states-in-warm-dense-aluminum-with-betatron-radiation
#19
M Z Mo, Z Chen, S Fourmaux, A Saraf, S Kerr, K Otani, R Masoud, J-C Kieffer, Y Tsui, A Ng, R Fedosejevs
Time-resolved measurements of the ionization states of warm dense aluminum via K-shell absorption spectroscopy are demonstrated using betatron radiation generated from laser wakefield acceleration as a probe. The warm dense aluminum is generated by irradiating a free-standing nanofoil with a femtosecond optical laser pulse and was heated to an electron temperature of ∼20-25 eV at a close-to-solid mass density. Absorption dips in the transmitted x-ray spectrum due to the Al^{4+} and Al^{5+} ions are clearly seen during the experiments...
May 2017: Physical Review. E
https://www.readbyqxmd.com/read/28558937/numerical-simulation-of-time-fractional-dual-phase-lag-model-of-heat-transfer-within-skin-tissue-during-thermal-therapy
#20
Dinesh Kumar, K N Rai
In this paper, we investigated the thermal behavior in living biological tissues using time fractional dual-phase-lag bioheat transfer (DPLBHT) model subjected to Dirichelt boundary condition in presence of metabolic and electromagnetic heat sources during thermal therapy. We solved this bioheat transfer model using finite element Legendre wavelet Galerkin method (FELWGM) with help of block pulse function in sense of Caputo fractional order derivative. We compared the obtained results from FELWGM and exact method in a specific case, and found a high accuracy...
July 2017: Journal of Thermal Biology
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