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https://www.readbyqxmd.com/read/28905516/simple-method-for-rf-pulse-measurement-using-gradient-reversal
#1
Vanessa L Landes, Krishna S Nayak
PURPOSE: To develop and evaluate a simple method for measuring the envelope of small-tip radiofrequency (RF) excitation waveforms in MRI, without extra hardware or synchronization. THEORY AND METHODS: Gradient reversal approach to evaluate RF (GRATER) involves RF excitation with a constant gradient and reversal of that gradient during signal reception to acquire the time-reversed version of an RF envelope. An outer-volume suppression prepulse is used optionally to preselect a uniform volume...
September 14, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28866489/simultaneous-ultrasonic-measurement-of-thickness-and-speed-of-sound-in-elastic-plates-using-coded-excitation-signals
#2
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/28862159/temporary-persistence-of-conduction-block-after-prolonged-kilohertz-frequency-alternating-current-khfac-on-rat-sciatic-nerve
#3
Narendra Bhadra, Emily Foldes, Tina Vrabec, Kevin L Kilgore, Niloy Bhadra
Application of Kilohertz Frequency Alternating Current (KHFAC) waveforms can result in nerve conduction block that is induced in less than a second. Conduction recovers within seconds when KHFAC is applied for about 5 - 10 minutes. This study investigated the effect of repeated and prolonged application of KHFAC on rat Sciatic nerve with bipolar platinum electrodes. Approach: Varying durations of KHFAC at signal amplitudes for conduction block with intervals of no stimulus were studied. Nerve conduction was monitored by recording peak Gastrocnemius muscle force utilizing stimulation electrodes proximal (PS) and distal (DS) to a blocking electrode...
September 1, 2017: Journal of Neural Engineering
https://www.readbyqxmd.com/read/28834777/improved-sensitivity-for-w-band-gd-iii-gd-iii-and-nitroxide-nitroxide-deer-measurements-with-shaped-pulses
#4
Thorsten Bahrenberg, Yael Rosenski, Raanan Carmieli, Koby Zibzener, Mian Qi, Veronica Frydman, Adelheid Godt, Daniella Goldfarb, Akiva Feintuch
Chirp and shaped pulses have been recently shown to be highly advantageous for improving sensitivity in DEER (double electron-electron resonance, also called PELDOR) measurements due to their large excitation bandwidth. The implementation of such pulses for pulse EPR has become feasible due to the availability of arbitrary waveform generators (AWG) with high sampling rates to support pulse shaping for pulses with tens of nanoseconds duration. Here we present a setup for obtaining chirp pulses on our home-built W-band (95GHz) spectrometer and demonstrate its performance on Gd(III)-Gd(III) and nitroxide-nitroxide DEER measurements...
August 10, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28834713/paramap-standardized-parameterization-of-sinoatrial-node-myocyte-action-potentials
#5
Christian Rickert, Catherine Proenza
Sinoatrial node myocytes act as cardiac pacemaker cells by generating spontaneous action potentials (APs). Much information is encoded in sinoatrial AP waveforms, but both the analysis and the comparison of AP parameters between studies is hindered by the lack of standardized parameter definitions and the absence of automated analysis tools. Here we introduce ParamAP, a standalone cross-platform computational tool that uses a template-free detection algorithm to automatically identify and parameterize APs from text input files...
August 22, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28828751/maturation-modulates-pharyngeal-stimulus-provoked-pharyngeal-and-respiratory-rhythms-in-human-infants
#6
Kathryn A Hasenstab, Swetha Sitaram, Ivan M Lang, Reza Shaker, Sudarshan R Jadcherla
Pharyngeal-provocation induced aerodigestive symptoms in infants remain an enigma. Sources of pharyngeal provocation can be anterograde as with feeding, and retrograde as in gastroesophageal reflux. We determined maturational and dose-response effects of targeted pharyngeal-stimulus on frequency, stability, and magnitude of pharyngeal and respiratory waveforms during multiple pharyngeal swallowing responses in preterm-born infants when they were of full-term postmenstrual age (PMA). Eighteen infants (11 male) were studied longitudinally at 39...
August 21, 2017: Dysphagia
https://www.readbyqxmd.com/read/28815597/cardiac-action-potential-repolarization-re-visited-early-repolarization-shows-all-or-none-behaviour
#7
Beatriz Trenor, Karen Cardona, Javier Saiz, Denis Noble, Wayne Giles
In healthy mammalian hearts the action potential (AP) waveform initiates and modulates each contraction, or heartbeat. As a result, action potential height and duration are key physiological variables. In addition, rate-dependent changes in ventricular action potential duration (APD), and variations in APD at a fixed heart rate, are both reliable biomarkers of electrophysiological stability. Present guidelines for the likelihood that candidate drugs will increase arrhythmias rely on small changes in APD and Q-T intervals as criteria for Safety Pharmacology decisions...
August 17, 2017: Journal of Physiology
https://www.readbyqxmd.com/read/28809704/kilohertz-electrical-stimulation-nerve-conduction-block-effects-of-electrode-material
#8
Yogi A Patel, Brian S Kim, Robert J Butera
Kilohertz electrical stimulation (KES) has enabled a novel new paradigm for spinal cord and peripheral nerve stimulation to treat a variety of neurological diseases. KES can excite or inhibit nerve activity and is used in many clinical devices today. However, the impact of different electrode materials on the efficacy of KES is unknown. We investigated the effect of different electrode materials and their respective charge injection mechanisms on KES nerve block thresholds using 20 and 40 kHz current-controlled sinusoidal KES waveforms...
August 10, 2017: IEEE Transactions on Neural Systems and Rehabilitation Engineering
https://www.readbyqxmd.com/read/28809681/a-prototype-therapy-system-for-transcutaneous-application-of-boiling-histotripsy
#9
Adam D Maxwell, Petr V Yuldashev, Wayne Kreider, Tatiana D Khokhlova, George R Schade, Timothy L Hall, Oleg A Sapozhnikov, Michael R Bailey, Vera A Khokhlova
Boiling histotripsy is a method of focused ultrasound surgery that noninvasively applies millisecond-length pulses with high-amplitude shock fronts to generate liquefied lesions in tissue. Such a technique requires unique outputs compared to a focused ultrasound thermal therapy apparatus, particularly to achieve high in situ pressure levels through intervening tissue. This article describes the design and characterization of a system capable of producing the necessary pressure to transcutaneously administer boiling histotripsy therapy through clinically relevant overlying tissue paths using pulses with duration up to 10 ms...
August 14, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28798205/cardiac-output-by-pulse-contour-analysis-does-not-match-the-increase-measured-by-rebreathing-during-human-spaceflight
#10
Richard L Hughson, Sean D Peterson, Nicholas J Yee, Danielle K Greaves
Pulse contour analysis of the non-invasive finger arterial pressure waveform provides a convenient means to estimate cardiac output (Q ̇). The method has been compared to standard methods under a range of conditions but never before during spaceflight. We compared pulse contour analysis with the Modelflow algorithm to estimates of Q ̇ obtained by rebreathing during pre-flight baseline testing and during the final month of long-duration spaceflight in nine healthy male astronauts. By Modelflow analysis, stroke volume was greater in supine baseline than seated baseline or inflight...
August 10, 2017: Journal of Applied Physiology
https://www.readbyqxmd.com/read/28780623/effect-of-a-photosensitization-reaction-performed-during-the-first-3%C3%A2-min-after-exposure-of-rat-myocardial-cells-to-talaporfin-sodium-in-vitro
#11
Marika Doi, Emiyu Ogawa, Tsunenori Arai
To better understand the mechanism of photodynamic cardiac ablation, we studied the effects of a photosensitization reaction (PR) performed during the first 3 min after rat myocardial cells were exposed to talaporfin sodium. A 3-mm-square microelectrode array with 64 electrodes was used to continuously measure the action potentials of the myocardial cells. A 30 μg/mL talaporfin sodium solution, a chlorine photosensitizer, was used, along with a 663-nm red diode laser (86 mW/cm(2) for up to 600 s). The first trough of the measured action potential waveform corresponding to Na(+) dynamics decreased exponentially with increasing PR duration...
August 5, 2017: Lasers in Medical Science
https://www.readbyqxmd.com/read/28751867/defects-in-vascular-mechanics-due-to-aging-in-rats-studies-on-arterial-wave-properties-from-a-single-aortic-pressure-pulse
#12
Chun-Yi Chang, Ru-Wen Chang, Shu-Hsien Hsu, Ming-Shiou Wu, Ya-Jung Cheng, Hsien-Li Kao, Liang-Chuan Lai, Chih-Hsien Wang, Kuo-Chu Chang
Changes in vascular mechanics due to aging include elevated vascular impedance, diminished aorta distensibility, and an accelerated return of pulse wave reflection, which may increase the systolic workload on the heart. Classically, the accurate measurement of vascular mechanics requires the simultaneous recording of aortic pressure and flow signals. In practice, it is feasible to estimate arterial wave properties in terms of wave transit time (τw) and wave reflection index (RI) by using aortic pressure signal alone...
2017: Frontiers in Physiology
https://www.readbyqxmd.com/read/28713053/perils-of-intraoperative-neurophysiological-monitoring-analysis-of-false-negative-results-in-spine-surgeries
#13
Arvydas A Tamkus, Kent S Rice, Michael T McCaffrey
BACKGROUND CONTEXT: Although some authors have published case reports describing false negatives in intraoperative neurophysiological monitoring (IONM), a systematic review of causes of false-negative IONM results is lacking. PURPOSE: The objective of this study was to analyze false-negative IONM findings in spine surgery. STUDY DESIGN: This is a retrospective cohort analysis. PATIENT SAMPLE: A cohort of 109 patients with new postoperative neurologic deficits was analyzed for possible false-negative IONM reporting...
July 13, 2017: Spine Journal: Official Journal of the North American Spine Society
https://www.readbyqxmd.com/read/28708655/utility-of-brainstem-trigeminal-evoked-potentials-in-patients-with-primary-trigeminal-neuralgia-treated-by-microvascular-decompression
#14
Jin Zhu, Xin Zhang, Hua Zhao, Yin-Da Tang, Ting-Ting Ying, Shi-Ting Li
OBJECTIVE: To investigate the characteristics of brainstem trigeminal evoked potentials (BTEP) waveform in patients with and without trigeminal neuralgia (TN), and to discuss the utility of BTEP in patients with primary TN treated by microvascular decompression (MVD). METHODS: A retrospective review of 43 patients who underwent BTEP between January 2016 and June 2016, including 33 patients with TN who underwent MVD and 10 patients without TN. Brainstem trigeminal evoked potentials characteristics of TN and non-TN were summarized, in particular to compare the BTEP changes between pre- and post-MVD, and to discover the relationship between BTEP changes and surgical outcome...
September 2017: Journal of Craniofacial Surgery
https://www.readbyqxmd.com/read/28701550/the-influence-of-envelope-waveform-on-itd-sensitivity-of-neurons-in-the-auditory-midbrain
#15
David Greenberg, Jessica Josephine Margaret Monaghan, Mathias Dietz, Torsten Marquardt, David McAlpine
Interaural time differences (ITDs) conveyed by the modulated envelopes of high-frequency sounds can serve as a cue for localising a sound source. Klein-Hennig et al. (2011) demonstrated the envelope attack, the rate at which stimulus energy in the envelope increases, and the duration of the pause, the interval between successive envelope pulses, as important factors affecting sensitivity to envelope ITDs in human listeners. Modulated sounds with rapid attacks and long pauses produce the lowest ITD-discrimination thresholds...
July 12, 2017: Journal of Neurophysiology
https://www.readbyqxmd.com/read/28699322/a-respiratory-marker-derived-from-left-vagus-nerve-signals-recorded-with-implantable-cuff-electrodes
#16
Cristian Sevcencu, Thomas N Nielsen, Benedict Kjaergaard, Johannes J Struijk
OBJECTIVE: Left vagus nerve (LVN) stimulation (LVNS) has been tested for lowering the blood pressure (BP) in patients with resistant hypertension (RH). Whereas, closed-loop LVNS (CL-LVNS) driven by a BP marker may be superior to open-loop LVNS, there are situations (e.g., exercising) when hypertension is normal. Therefore, an ideal anti-RH CL-LVNS system requires a variable to avoid stimulation in such conditions, for example, a respiratory marker ideally extracted from the LVN. As the LVN conducts respiratory signals, this study aimed to investigate if such signals can be recorded using implantable means and if a marker to monitor respiration could be derived from such recordings...
July 11, 2017: Neuromodulation: Journal of the International Neuromodulation Society
https://www.readbyqxmd.com/read/28676704/biomaterial-free-three-dimensional-bioprinting-of-cardiac-tissue-using-human-induced-pluripotent-stem-cell-derived-cardiomyocytes
#17
Chin Siang Ong, Takuma Fukunishi, Huaitao Zhang, Chen Yu Huang, Andrew Nashed, Adriana Blazeski, Deborah DiSilvestre, Luca Vricella, John Conte, Leslie Tung, Gordon F Tomaselli, Narutoshi Hibino
We have developed a novel method to deliver stem cells using 3D bioprinted cardiac patches, free of biomaterials. Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), fibroblasts (FB) and endothelial cells (EC) were aggregated to create mixed cell spheroids. Cardiac patches were created from spheroids (CM:FB:EC = 70:15:15, 70:0:30, 45:40:15) using a 3D bioprinter. Cardiac patches were analyzed with light and video microscopy, immunohistochemistry, immunofluorescence, cell viability assays and optical electrical mapping...
July 4, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28666708/sound-offset-related-brain-potentials-show-retained-sensory-processing-but-increased-cognitive-control-activity-in-older-adults
#18
János Horváth, Zsófia Anna Gaál, Márta Volosin
It has been hypothesized that age-related hearing loss is caused not only by peripheral but also central changes in the auditory system. Many studies used event-related potentials (ERPs) elicited by sound onsets to characterize the age-related differences in central auditory processing. Age-related ERP enhancements in such studies have often been interpreted in terms of elevated sensitivity to auditory stimulation. Such ERPs, however, comprise various components reflecting different aspects of auditory and task-related processing...
September 2017: Neurobiology of Aging
https://www.readbyqxmd.com/read/28662588/utilization-of-multiple-spinal-cord-stimulation-scs-waveforms-in-chronic-pain-patients
#19
Anthony P Berg, Nitzan Mekel-Bobrov, Edward Goldberg, Dat Huynh, Roshini Jain
BACKGROUND: Advances in spinal cord stimulation (SCS) have improved patient outcomes, leading to its increased utilization for chronic pain. Chronic pain is dynamic showing exacerbations, variable severity, and evolving pain patterns. Given this complexity, SCS systems that provide a broad range of stimulation waveforms may be valuable. METHODS: The aim of this research was to characterize the usage pattern of stimulation waveforms and field shapes in chronic pain patients implanted with the Spectra System...
July 12, 2017: Expert Review of Medical Devices
https://www.readbyqxmd.com/read/28660445/serum-adipocyte-fatty-acid-binding-protein-level-is-associated-with-arterial-stiffness-quantified-with-cardio-ankle-vascular-index-in-kidney-transplant-patients
#20
Yen-Cheng Chen, Bang-Gee Hsu, Chung-Jen Lee, Ching-Chun Ho, Guan-Jin Ho, Ming-Che Lee
BACKGROUND: Arterial stiffness is an established marker of cardiovascular risk and an independent predictor of cardiovascular disease (CVD) events and mortality in kidney transplant (KT) patients. Adipocyte fatty acid-binding protein (A-FABP), a novel adipokine, is positively associated with atherosclerosis. The present study evaluated the relationship between fasting circulating A-FABP and peripheral arterial stiffness using the cardio-ankle vascular index (CAVI) in KT patients. METHODS: Fasting blood samples were collected from 74 KT patients, and serum A-FABP levels were measured using an enzyme immunoassay...
June 28, 2017: Clinical and Experimental Nephrology
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