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Non-invasive Picosecond Pulse System for Electrostimulation

机译:用于电刺激的无创皮秒脉冲系统

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Picosecond pulsed electric fields have been shown to have stimulatory effects, such as calcium influx, activation of action potential, and membrane depolarization, on biological cells. Because the pulse duration is so short, it has been hypothesized that the pulses permeate a cell and can directly affect intracellular cell structures by bypassing the shielding of the membrane. This provides an opportunity for studying new biophysics. Furthermore, radiating picosecond pulses can be efficiently done by a compact antenna because the antenna size is comparable to the pulse width. However, all of the previous bioelectric studies regarding picosecond pulses have been conducted in vitro, using electrodes. There is not yet a device which can non-invasively deliver picosecond-pulsed electric fields to neurological tissue for therapeutic applications. It is unclear whether a radiated electric field at a given penetration depth can reach the threshold to cause biological effects.;In this dissertation, a picosecond- pulsed electric field system designed for the electrosimulation of neural cells is presented. This begins with the design of an ultra-wideband biconical dielectric rod antenna. It consists of a dielectrically loaded V-conical launcher which feeds a cylindrical waveguide. The waveguide then transitions into a taper, which acts like a lens to focus the energy in the tissue target. To describe the antenna delivery of picosecond pulses to tissues, the initial performance was simulated using a 3-layer tissue model and then a human head model. The final model was shown to effectively deliver pulses of 11.5 V/m to the brain for a 1 V input. The spot size of the stimulation is on the order of 1 cm. The electric field was able to penetrate to a depth of 2 cm, which is equal to the pulse width of a 200 ps pulse. The antenna was constructed and characterized in free space in time domain and in frequency domain. The experimental results have a good agreement with the simulation.;The ultimate biological application relies on adequate electric field. To reach a threshold electric field for effective stimulation, the antenna should be driven by a high voltage, picosecond-pulsed power supply, which, in our case, consists of a nanosecond charging transformer, a parallel-plate transmission line, and a picosecond discharging switch. This transformer was used to charge a parallel-plate transmission line, with the antenna as the load. To generate pulses with a rise time of hundreds of picoseconds, an oil switch with a millimeter gap was used. For the charging, a dual resonance pulse transformer was designed and constructed. The novel aspect of this transformer is has a fast charge time. It was shown to be capable of producing over 100 kV voltages in less than 100 ns. After the closing of the peaking switch and the picosecond rise time generation, the antenna was able to create an electric field of 600 V/cm in the air at a distance of 3 cm. This field was comparable to the simulation. Higher voltage operation was met with dielectric breakdown across the insulation layer that separates the high voltage side and the ground side.;Before the designed antenna is used in vivo, it is critical to determine the biological effect of picosecond pulses. This is especially important if we focus on stimulatory effects, which require that the electric field intensity be close to the range that the antenna system can deliver. Toward that end, neural stem cells were chosen to study for the proliferation, metabolism, and gene expression. Instead of using the antenna, the electrodes were used to deliver the pulses to the cells. In order to treat enough cells for downstream analyses, the electrodes were mounted on a 3-D printer head, which could be moved freely and could be controlled accurately by programming. The results show that pulses on the order of 20 kV/cm affect the proliferation, metabolism, and gene expression of both neural and mesenchymal stem cells, without reducing viability.;In general, we came to the conclusion that picosecond pulses can be a useful stimulus for a variety of applications, but the possibility of using antennas to directly stimulate tissue functions relies on the development of a pulsed power system, high voltage insulation, and antenna material.
机译:皮秒脉冲电场已显示对生物细胞具有刺激作用,例如钙流入,动作电位激活和膜去极化。因为脉冲持续时间太短,所以已经假设脉冲渗透到细胞中并且可以通过绕过膜的屏蔽而直接影响细胞内细胞结构。这为研究新的生物物理学提供了机会。此外,由于天线尺寸可与脉冲宽度相比,因此可以通过紧凑型天线有效地完成皮秒辐射脉冲。但是,所有先前有关皮秒脉冲的生物电学研究都是使用电极在体外进行的。还没有一种设备可以将皮秒脉冲电场无创地输送到神经组织以进行治疗。目前尚不清楚给定穿透深度的辐射电场是否能够达到引起生物学效应的阈值。本文提出了一种用于神经细胞电模拟的皮秒脉冲电场系统。这始于超宽带双锥介电棒状天线的设计。它由一个装有电介质的V形锥形发射器组成,该发射器为圆柱形波导供电。然后,波导过渡到锥度,锥度像透镜一样将能量聚焦在组织目标中。为了描述皮秒脉冲向组织的天线传输,使用3层组织模型,然后再用人头模型模拟了初始性能。最终模型显示出,对于1 V输入,可以有效地向大脑传递11.5 V / m的脉冲。刺激的光斑大小约为1 cm。电场能够穿透到2 cm的深度,该深度等于200 ps脉冲的脉冲宽度。在时域和频域的自由空间中构造并表征了天线。实验结果与仿真结果吻合良好。最终的生物学应用取决于足够的电场。为了达到有效刺激的阈值电场,天线应该由高压,皮秒脉冲电源驱动,在本例中,该电源由纳秒充电变压器,平行板传输线和皮秒放电组成开关。该变压器用于以天线为负载为平行板传输线充电。为了产生上升时间为数百皮秒的脉冲,使用了具有毫米间隙的油开关。为了充电,设计并构造了双谐振脉冲变压器。该变压器的新颖之处在于具有快速充电时间。它被证明能够在不到100 ns的时间内产生超过100 kV的电压。闭合峰值开关并产生皮秒上升时间后,天线能够在3 cm的距离的空气中产生600 V / cm的电场。该领域与模拟相当。更高的工作电压通过绝缘层击穿绝缘层,使绝缘层击穿,绝缘层将高压侧和接地侧隔离开来。如果我们关注刺激效应,这尤其重要,刺激效应要求电场强度接近天线系统可提供的范围。为此,选择了神经干细胞来研究其增殖,代谢和基因表达。代替使用天线,而是使用电极将脉冲传递到单元。为了处理足够的细胞以进行下游分析,将电极安装在3-D打印机头上,该头可以自由移动并可以通过编程精确控制。结果表明,大约20 kV / cm的脉冲会影响神经和间充质干细胞的增殖,代谢和基因表达,而不会降低活力。总的来说,我们得出的结论是皮秒脉冲可能是有用的。刺激可以用于各种应用,但是使用天线直接刺激组织功能的可能性取决于脉冲电源系统,高压绝缘和天线材料的发展。

著录项

  • 作者

    Petrella, Ross Aaron.;

  • 作者单位

    Old Dominion University.;

  • 授予单位 Old Dominion University.;
  • 学科 Biomedical engineering.;Electrical engineering.;Electromagnetics.
  • 学位 Ph.D.
  • 年度 2018
  • 页码 123 p.
  • 总页数 123
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 古生物学;
  • 关键词

  • 入库时间 2022-08-17 11:53:11

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