降低功耗的高频磁刺激仪电路参数优化设计及仿真

针对重复经颅磁刺激仪功率消耗高的问题，我们通过建立电路模型，利用MATLAB平台进行仿真计算，研究了一种对放电的剩余能量进行有效回收的方法，并对磁刺激仪充放电及电能回收电路进行了设计，同时利用MCU实现了对电路充放电的智能控制。通过NI的Multisim平台对电能回收电路进行了仿真验证。仿真结果表明，本研究设计的电能回收电路，能使放电能量的回收率达到21％，从而降低了重复经颅磁刺激系统的功耗，提高了电能的利用效率。     

重复经颅磁刺激仪的优化设计

本文建立了RLC磁刺激仪模型 ,给出了模型参数计算方法。将磁刺激系统的性能指标分为三部分 :反映磁刺激仪输出性能的损耗能量 ;反映线圈输出性能的峰值磁能 ;反映线圈结构的几何变量。在给定磁刺激条件下 ,调整平面螺旋线圈的结构并计算出依赖于线圈结构参数的磁刺激仪和线圈输出性能值 ,从而 ,寻找最优的系统参数。优化结果表明 :线圈外半径和线的直径 (或截面面积 )是关键因素 ,选择合适的线圈外半径和线结构可以大大降低功耗 ,提高磁刺激频率 ,解决线圈发热问题     

微机式磁刺激系统的设计仿真与建模研究

磁刺激技术作为医学康复一种非侵入式的诊疗技术,是当前该领域国际范围的一项重要的研究课题.目前,所用的磁刺激仪存在两大问题:①磁线圈聚焦性较差;②系统能耗较大.刺激阈值所需要的能耗大,由此仪器产热并造成刺激有效性降低.本文在近几年磁刺激技术研究的基础上,运用计算机对磁刺激系统的重要模块进行了仿真,其中包括主电路与微机控制电路的仿真,并对磁刺激线圈磁场进行建模研究,为日后的研究和实践提供了有益的理论依据.     

经颅磁刺激线圈的磁聚焦优化设计

经颅磁刺激是利用变化磁场产生的感应电场作用于可兴奋人体脑组织的过程,磁聚焦性能是经颅磁刺激线圈设计的一项重要指标。根据磁刺激线圈感应电场理论,我们设计了半圆螺线管用于经颅磁刺激,计算了其载流线圈随刺激深度的感应电场分布,并与传统的经颅磁刺激8字形线圈作比较。结果表明,半圆螺旋管线圈既继承了8字形线圈感应电场的主瓣聚焦性强的优良特性,又摒弃了其相对较大的旁瓣对浅表非靶组织的兴奋刺激的不良影响,完全达到了磁聚焦优化设计的目的,也更利于磁刺激兴奋点的定位。     

重复经颅磁刺激治疗抑郁症的刺激参数的研究进展

重复经颅磁刺激是在经颅磁刺激基础上发展起来的新的神经电生理技术,它利用磁场作用于大脑皮质产生感应电流来改变皮质神经细胞的动作电位,从而影响脑内代谢和神经电活动。本文简单综述了重复经颅磁刺激治疗抑郁症的部分刺激参数。     

经颅磁刺激的多尺度建模仿真研究

经颅磁刺激是一种无创无痛的电磁刺激手段,被广泛应用于神经调控,在临床上对多种精神疾病和神经类疾病有明显的治疗效果。本文从电磁场建模仿真,细胞跨膜电位建模仿真,以及神经元响应建模仿真3个方面对经颅磁刺激多尺度建模仿真研究进行了详细的综述,并提出现阶段存在的问题以及对未来的展望。经颅磁刺激的多尺度建模仿真对磁刺激仪的设计开发具有指导意义,对磁刺激的导航系统提供重要的理论基础,有助于我们更好的理解电磁刺激的神经调控机制。     

脑磁刺激空间感应电场分布的数学模型与计算机仿真

本研究建立了脑神经磁刺激研究中较常用的八字线圈感应电场分布的半无界空间数学模型 ,应用数值积分和图形旋转与消隐技术建立了计算机仿真方法 ,据此分析了八字线圈感应电场空间分布的特性 ,为设计具有更好空间定位性和矢量选择性的脑神经磁刺激线圈提供了有效的仿真手段和研究方法。     

面向鸽子机器人的磁刺激线圈仿真设计及实验研究

为了探究将磁刺激技术应用于动物机器人运动控制的可行性,本文面向鸽子机器人,仿真分析线圈半径、匝数等因素对磁刺激强度、深度及聚焦性的影响,提出线圈设计方案。将线圈置于鸽子头部及腿部,磁刺激同时记录腿部肌电。结果发现,磁刺激时肌电明显增强。降低磁刺激系统输出频率,输出电流增大,肌电随之增强。与脑部磁刺激相比,刺激坐骨神经引起的肌电增强反应更为显著。这表明,磁刺激系统通过驱动该线圈可以有效地实现对脑及外周神经功能的调控。本研究为后续实用性线圈优化改进提供了理论及实验指导,为动物机器人磁刺激运动控制实施奠定了初步的理论和实验基础。     

磁刺激应用及机理研究进展

由于磁刺激技术的有效性和无创性 ,近年来该技术已被应用于临床治疗及脑科学的研究中。本文综述了磁刺激对各种神经性疾病的治疗作用 ,并阐述其主要的作用机理     

核医学仪器科学中的电路仿真

目的：核电子学可应用到核医学诊断领域,为核医学研究提供硬件支持。提高核仪器的电路性能可从根本上促进核医学的发展。借助电路仿真,本文研究核电子学中一个重要的基本部件,电荷灵敏前置放大器。该前置放大器在高分辨率能谱测量系统中有着广泛的应用。方法：我们利用Pspice,orCAD电路仿真软件,对电荷灵敏前置放大器的基本电路,进行了温度效应、噪声效应和其他主要性能指标的仿真分析,并与理论值进行了比较。通过调节电路参数,可动态观察输出结果如输出电压波形,并可形象地观察工作温度的变化对输出信号和输出噪声的影响,从而了解电路指标的温度效应。结果：对变换增益和平均计数率等主要电路参数的仿真结果和理论一致。泄放电阻的使用可以释放累加的电荷信号,使放大器工作在线性范围。分布电容是产生前置放大器噪声的主要原因,减小噪声必须减小分布电容。输出噪声在正常的工作频率范围内,会随温度增加而增大。结论：在高分辨率能谱分析仪设计中,使探测器和前置放大器系统的信噪比最大化是至关重要的。充分考虑电路的温度和噪声等效应是设计高性能前置放大器的基础,有助设计低噪声的前置放大器。电路仿真具有实现快、输出结果形象、可将如噪声效应抽离进行分析等特点,在核电子学以及医学仪器设计方面有广泛的应用空间。     

聚偏二氟乙烯膜的压电仿真及结构优化

聚偏二氟乙烯（PVDF）可用于设计贴合人体的柔性压力传感器,具有广泛的研究和应用前景。但 PVDF 的压电常数低,传感器灵敏度受到限制。为了研究 PVDF 膜在应用于压力传感器时的压电性能,利用 COMSOL 建立压电仿真模型,计算稳态下 PVDF 膜承受低压力载荷产生的电势、表面电荷密度及应力分布。对比仿真结果与理论计算值,验证了所建立的仿真方法和仿真模型的正确性。仿真发现,采用刚性基底的 PVDF 膜在长、宽方向产生的应力对压电性能有减弱作用,进一步验证了通过缩减 PVDF 膜的长、宽,可以提升压电性能的几何结构优化方法。此外,仿真对比了刚性、柔性基底下PVDF 膜的应力状态,并发现柔性基底下的应力状态可导致明显更高的压电输出。该研究结合了仿真方法与压电理论,可以为 PVDF 材料的其他基础研究提供方法参考,研究结果可以为 PVDF 柔性压力传感器的结构设计和优化提供启发,以期获得更高的传感器灵敏度。     

Orientation-specific fast rTMS maximizes corticospinal inhibition and facilitation

Specific stimulation of neuronal circuits may promote selective inhibition or facilitation of corticospinal tract excitability. Monophasic stimulation is more likely to achieve direction-specific neuronal excitation. In 10 healthy subjects, we compared four types of repetitive transcranial magnetic stimulation (rTMS), monophasic and biphasic stimuli with the initial current in the brain flowing antero-posteriorly (posteriorly directed) or postero-anteriorly (anteriorly directed). We applied rTMS over the primary motor cortex contralateral to the dominant hand, using 80 stimuli at 5 Hz frequency at an intensity yielding baseline motor evoked potential (MEP) amplitudes of 1 mV. Monophasic stimulation was always more efficient than biphasic. Facilitation was induced by intracerebral anteriorly directed current flow and inhibition by posteriorly oriented current flow, although only initially for approximately 30 pulses. The early inhibition was absent when studied during a tonic muscle contraction. Several mechanisms could account for these findings. They include a more efficient excitation of inhibiting circuits by posteriorly oriented pulses, and a back-propagating D-wave inhibiting early I-waves and thus inducing early inhibition of MEP amplitude. In any case biphasic rTMS results can be explained by a mixture of monophasic opposite stimulations. We propose the use of monophasic pulses for maximizing effects during rTMS.     

The Effectiveness of Electronic Screening and Brief Intervention for Reducing Levels of Alcohol Consumption: A Systematic Review and Meta-Analysis

Background

Electronic screening and brief intervention (eSBI) has been shown to reduce alcohol consumption, but its effectiveness over time has not been subject to meta-analysis.

Objective

The current study aims to conduct a systematic review and meta-analysis of the available literature to determine the effectiveness of eSBI over time in nontreatment-seeking hazardous/harmful drinkers.

Methods

A systematic review and meta-analysis of relevant studies identified through searching the electronic databases PsychINFO, Medline, and EMBASE in May 2013. Two members of the study team independently screened studies for inclusion criteria and extracted data. Studies reporting data that could be transformed into grams of ethanol per week were included in the meta-analysis. The mean difference in grams of ethanol per week between eSBI and control groups was weighted using the random-effects method based on the inverse-variance approach to control for differences in sample size between studies.

Results

There was a statistically significant mean difference in grams of ethanol consumed per week between those receiving an eSBI versus controls at up to 3 months (mean difference –32.74, 95% CI –56.80 to –8.68, z=2.67, P=.01), 3 to less than 6 months (mean difference –17.33, 95% CI –31.82 to –2.84, z=2.34, P=.02), and from 6 months to less than 12 months follow-up (mean difference –14.91, 95% CI –25.56 to –4.26, z=2.74, P=.01). No statistically significant difference was found at a follow-up period of 12 months or greater (mean difference –7.46, 95% CI –25.34 to 10.43, z=0.82, P=.41).

Conclusions

A significant reduction in weekly alcohol consumption between intervention and control conditions was demonstrated between 3 months and less than 12 months follow-up indicating eSBI is an effective intervention.     

Perturbation of visuospatial attention by high-frequency offline rTMS

The contribution of different cortical regions to visuospatial attention can be probed with the help of perturbation techniques, such as transcranial magnetic stimulation (TMS). Repetitive TMS (rTMS) has also been suggested as a tool for the therapy of brain injuries, by adjusting the neural excitability of injured or intact brain regions. Low- and high-frequency rTMS have been shown to result in subsequent (offline) reductions or increases of local cortical excitability, respectively. Previous studies demonstrated that low-frequency (1 Hz) rTMS of posterior parietal cortex (PPC) produced significantly reduced detection of stimuli in the visual hemifield contralateral to the stimulation site, as well as increased ipsilateral detection. We here explored the functional impact of high-frequency (20 Hz) rTMS with an attention task similar to that of a previous low-frequency study (Hilgetag et al. in Nat Neurosci 4:953–957, 2001). Normal healthy subjects (N = 14) received high-frequency rTMS (20 Hz, 10 min, 50% stimulator output) over right or left PPC (coordinate points P4 or P3). After stimulation of the right PPC, detection of single visual stimuli in the contralateral hemifield was significantly impaired. Generally, rTMS of right and left PPC produced mirror-symmetric trends in reduced contralateral detection. These effects were still present after post-TMS sham stimulation (more than 20 min after the end of active rTMS). The results suggest that attentional function can be perturbed by high-frequency rTMS as well as by low-frequency rTMS, despite potential differences in the underlying neural mechanisms. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Biomechanical Analysis of Reducing Sacroiliac Joint Shear Load by Optimization of Pelvic Muscle and Ligament Forces

Effective stabilization of the sacroiliac joints (SIJ) is essential, since spinal loading is transferred via the SIJ to the coxal bones, and further to the legs. We performed a biomechanical analysis of SIJ stability in terms of reduced SIJ shear force in standing posture using a validated static 3-D simulation model. This model contained 100 muscle elements, 8 ligaments, and 8 joints in trunk, pelvis, and upper legs. Initially, the model was set up to minimize the maximum muscle stress. In this situation, the trunk load was mainly balanced between the coxal bones by vertical SIJ shear force. An imposed reduction of the vertical SIJ shear by 20% resulted in 70% increase of SIJ compression force due to activation of hip flexors and counteracting hip extensors. Another 20% reduction of the vertical SIJ shear force resulted in further increase of SIJ compression force by 400%, due to activation of the transversely oriented M. transversus abdominis and pelvic floor muscles. The M. transversus abdominis crosses the SIJ and clamps the sacrum between the coxal bones. Moreover, the pelvic floor muscles oppose lateral movement of the coxal bones, which stabilizes the position of the sacrum between the coxal bones (the pelvic arc). Our results suggest that training of the M. transversus abdominis and the pelvic floor muscles could help to relieve SI-joint related pelvic pain.