Current Issue : October - December Volume : 2018 Issue Number : 4 Articles : 5 Articles
Commercially available electrodes can only provide quality surface electromyography\n(sEMG) measurements for a limited duration due to user discomfort and signal degradation, but\nin many applications, collecting sEMG data for a full day or longer is desirable to enhance clinical\ncare. Few studies for long-term sEMG have assessed signal quality of electrodes using clinically\nrelevant tests. The goal of this research was to evaluate flexible, gold-based epidermal sensor system\n(ESS) electrodes for long-term sEMG recordings. We collected sEMG and impedance data from eight\nsubjects from ESS and standard clinical electrodes on upper extremity muscles during maximum\nvoluntary isometric contraction tests, dynamic range of motion tests, the Jebsen Taylor Hand Function\nTest, and the Box & Block Test. Four additional subjects were recruited to test the stability of ESS\nsignals over four days. Signals from the ESS and traditional electrodes were strongly correlated\nacross tasks. Measures of signal quality, such as signal-to-noise ratio and signal-to-motion ratio, were\nalso similar for both electrodes. Over the four-day trial, no significant decrease in signal quality was\nobserved in the ESS electrodes, suggesting that thin, flexible electrodes may provide a robust tool\nthat does not inhibit movement or irritate the skin for long-term measurements of muscle activity in\nrehabilitation and other applications....
Background: Deep brain stimulation (DBS) has shown wide clinical applications for\ntreating various disorders of central nervous system. High frequency stimulation (HFS)\nof pulses with a constant intensity and a constant frequency is typically used in DBS.\nHowever, new stimulation paradigms with time-varying parameters provide a prospective\ndirection for DBS developments. To meet the research demands for time-varying\nstimulations, we designed a new stimulation system with a technique of LabVIEWbased\nvirtual instrument.\nMethods: The system included a LabVIEW program, a NI data acquisition card, and an\nanalog stimulus isolator. The output waveforms of the system were measured to verify\nthe time-varying parameters. Preliminary animal experiments were run by delivering\nthe HFS sequences with time-varying parameters to the hippocampal CA1 region of\nanesthetized rats.\nResults: Verification results showed that the stimulation system was able to generate\npulse sequences with ramped intensity and hyperbolic frequency accurately.\nApplication of the time-varying HFS sequences to the axons of pyramidal cells in the\nhippocampal CA1 region resulted in neuronal responses different from those induced\nby HFS with constant parameters. The results indicated important modulations of timevarying\nstimulations to the neuronal activity that could prevent the stimulation from\ninducing over-synchronized firing of population neurons.\nConclusions: The stimulation system provides a useful technique for investigating\ndiverse stimulation paradigms for the development of new DBS treatments....
Objective: This study aimed to investigate the influence of injection rates of calibrating\nstandard solution on monitoring pulse indicator continuous cardiac output (PICCO,\nmade in Germany), and thereby to provide significant references for clinical practice.\nMethods: A total of 108 critical patients in stroke intensive care unit were identified.\nAll these participants received transesophageal cardiac color Doppler ultrasound, and\nwithin 15 min PICCO equipment was utilized to monitor the relevant parameters, by\nmeans of 0 Ã?°C calibrating standard solution, and the injection speeds were 2ââ?¬â??4, 5ââ?¬â??7,\nand 8ââ?¬â??10 s. Besides, the monitoring indicators were as follows, cardiac index, global\nejection fraction, global end diastolic volume index. The potential correlations were\nevaluated between PICCO and transesophageal cardiac color Doppler ultrasound.\nResults: All the data was available, and the monitored parameters of PICOO at\n2ââ?¬â??4, 5ââ?¬â??7, and 8ââ?¬â??10 s were positively correlated with the parameters obtained from\ntransesophageal cardiac color Doppler ultrasound (P < 0.05). Specially, it is worth\nemphasizing that the best correlation between them could be provided when the\ninjection rate was 2ââ?¬â??4 s.\nConclusion: When the injection rate at 2ââ?¬â??4 s, the parameters obtained by PICOO were\nmuch closer to that of transesophageal cardiac color Doppler ultrasound. Furthermore,\nthe parameters of PICOO obtained at 2ââ?¬â??4 s could better reflect cardiac function of\npatients....
Background: Noninvasive magnetic resonance thermometry (MRT) at low-field\nusing proton resonance frequency shift (PRFS) is a promising technique for monitoring\nablation temperature, since low-field MR scanners with open-configuration are more\nsuitable for interventional procedures than closed systems. In this study, phase-drift\ncorrection PRFS with first-order polynomial fitting method was proposed to investigate\nthe feasibility and accuracy of quantitative MR thermography during hyperthermia\nprocedures in a 0.35 T open MR scanner.\nMethods: Unheated phantom and ex vivo porcine liver experiments were performed\nto evaluate the optimal polynomial order for phase-drift correction PRFS. The temperature\nestimation approach was tested in brain temperature experiments of three\nhealthy volunteers at room temperature, and in ex vivo porcine liver microwave ablation\nexperiments. The output power of the microwave generator was set at 40 W for\n330 s. In the unheated experiments, the temperature root mean square error (RMSE) in\nthe inner region of interest was calculated to assess the best-fitting order for polynomial\nfit. For ablation experiments, relative temperature difference profile measured by\nthe phase-drift correction PRFS was compared with the temperature changes recorded\nby fiber optic temperature probe around the microwave ablation antenna within the\ntarget thermal region.\nResults: The phase-drift correction PRFS using first-order polynomial fitting could\nachieve the smallest temperature RMSE in unheated phantom, ex vivo porcine liver\nand in vivo human brain experiments. In the ex vivo porcine liver microwave ablation\nprocedure, the temperature error between MRT and fiber optic probe of all but six\ntemperature points were less than 2 �°C. Overall, the RMSE of all temperature points was\n1.49 �°C.\nConclusions: Both in vivo and ex vivo experiments showed that MR thermometry\nbased on the phase-drift correction PRFS with first-order polynomial fitting could be\napplied to monitor temperature changes during microwave ablation in a low-field\nopen-configuration whole-body MR scanner....
Background: Although accurate modeling of the thermal performance of irrigated-tip\nelectrodes in radiofrequency cardiac ablation requires the solution of a triple coupled\nproblem involving simultaneous electrical conduction, heat transfer, and fluid dynamics,\nin certain cases it is difficult to combine the software with the expertise necessary\nto solve these coupled problems, so that reduced models have to be considered. We\nhere focus on a reduced model which avoids the fluid dynamics problem by setting a\nconstant temperature at the electrode tip. Our aim was to compare the reduced and\nfull models in terms of predicting lesion dimensions and the temperatures reached in\ntissue and blood.\nResults: The results showed that the reduced model overestimates the lesion surface\nwidth by up to 5 mm (i.e. 70%) for any electrode insertion depth and blood flow rate.\nLikewise, it drastically overestimates the maximum blood temperature by more than\n15 �°C in all cases. However, the reduced model is able to predict lesion depth reasonably\nwell (within 0.1 mm of the full model), and also the maximum tissue temperature\n(difference always less than 3 �°C). These results were valid throughout the entire\nablation time (60 s) and regardless of blood flow rate and electrode insertion depth\n(ranging from 0.5 to 1.5 mm).\nConclusions: The findings suggest that the reduced model is not able to predict\neither the lesion surface width or the maximum temperature reached in the blood,\nand so would not be suitable for the study of issues related to blood temperature,\nsuch as the incidence of thrombus formation during ablation. However, it could be\nused to study issues related to maximum tissue temperature, such as the steam pop\nphenomenon....
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