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pulse transmit time

I Ughratdar, K A Kawsar, R Mitchell, R Selway, K Ashkan
BACKGROUND: Battery replacement or revision surgery for neuromodulation implants is conventionally performed using sharp dissection. Meticulous dissection within thick scar tissue is vital to avoid damage to surrounding lead(s) which could result in more extensive revision surgery. Traditional electrosurgery devices are contraindicated as the emitted energy can be transferred to the hardware resulting in implant or tissue damage with severe consequent complications. OBJECTIVE: We report our experience and potential applications of a novel, pulsed monopolar radiofrequency energy device (PEAK PlasmaBlade™, Medtronic plc) which facilitates dissection around implants without the risk of damaging or transmitting energy through the system...
January 9, 2018: World Neurosurgery
Heather V Kenny, Amber N Wright, Jonah Piovia-Scott, Louie H Yang, David A Spiller, Thomas W Schoener
Resource pulses are brief periods of unusually high resource abundance. While population and community responses to resource pulses have been relatively well studied, how individual consumers respond to resource pulses has received less attention. Local consumers are often the first to respond to a resource pulse, and the form and timing of individual responses may influence how the effects of the pulse are transmitted throughout the community. Previous studies in Bahamian food webs have shown that detritivores associated with pulses of seaweed wrack provide an alternative prey source for lizards...
December 2017: Ecology and Evolution
Martin Pekař, Nenad Mihajlović, Harm Belt, Alexander F Kolen, Jeannet van Rens, Frank Budzelaar, Bas Jacobs, Johan G Bosch, Hendrik J Vos, Debbie Rem-Bronneberg, Gijs van Soest, Antonius F W van der Steen
Commercially available intracardiac echo (ICE) catheters face a trade-off between viewing depth and resolution. Frequency-tunable ICE probes would offer versatility of choice between penetration or resolution imaging within a single device. In this phantom study, the imaging performance of a novel, frequency-tunable, 32-element, 1-D CMUT array integrated with front-end electronics is evaluated. Phased-array ultrasound imaging with a forward-looking CMUT probe prototype operated beyond collapse mode at voltages up to three times higher than the collapse voltage (-65 V) is demonstrated...
December 14, 2017: Ultrasonics
Keren Constantini, Abigail S L Stickford, Jeffery L Bleich, Paul D Mannheimer, Benjamin D Levine, Robert F Chapman
Timing foot strike to occur in synchrony with cardiac diastole may reduce left ventricular afterload and promote coronary and skeletal muscle perfusion. PURPOSE: To assess heart rate (HR) and metabolic responses to running when foot strikes are timed to occur exclusively during 1) the systolic phase of the cardiac cycle, or 2) the diastolic phase. METHODS: Ten elite male distance runners performed a testing session on a treadmill at 4.72 m[BULLET OPERATOR]s while matching their steps to an auditory tone and wearing a chest strap that transmitted accelerometer and ECG signals...
December 12, 2017: Medicine and Science in Sports and Exercise
Vincent Gras, Franck Mauconduit, Alexandre Vignaud, Alexis Amadon, Denis Le Bihan, Tony Stöcker, Nicolas Boulant
PURPOSE: T2 -weighted sequences are particularly sensitive to the radiofrequency (RF) field inhomogeneity problem at ultra-high-field because of the errors accumulated by the imperfections of the train of refocusing pulses. As parallel transmission (pTx) has proved particularly useful to counteract RF heterogeneities, universal pulses were recently demonstrated to save precious time and computational efforts by skipping B1 calibration and online RF pulse tailoring. Here, we report a universal RF pulse design for non-selective refocusing pulses to mitigate the RF inhomogeneity problem at 7T in turbo spin-echo sequences with variable flip angles...
November 29, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Vyacheslav A Trofimov, Svetlana A Varentsova, Irina G Zakharova, Dmitry Yu Zagursky
Using an experiment with thin paper layers and computer simulation, we demonstrate the principal limitations of standard Time Domain Spectroscopy (TDS) based on using a broadband THz pulse for the detection and identification of a substance placed inside a disordered structure. We demonstrate the spectrum broadening of both transmitted and reflected pulses due to the cascade mechanism of the high energy level excitation considering, for example, a three-energy level medium. The pulse spectrum in the range of high frequencies remains undisturbed in the presence of a disordered structure...
November 25, 2017: Sensors
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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