Table_1_Steering the Volume of Tissue Activated With a Directional Deep Brain Stimulation Lead in the Globus Pallidus Pars Interna: A Modeling Study With Heterogeneous Tissue Properties.DOCX

Objective: To study the effect of directional deep brain stimulation (DBS) electrode configuration and vertical electrode spacing on the volume of tissue activated (VTA) in the globus pallidus, pars interna (GPi).Background: Directional DBS leads may allow clinicians to precisely direct current fields to different functional networks within traditionally targeted brain areas. Modeling the shape and size of the VTA for various monopolar or bipolar configurations can inform clinical programming strategies for GPi DBS. However, many computational models of VTA are limited by assuming tissue homogeneity.Methods: We generated a multimodal image-based detailed anatomical (MIDA) computational model with a directional DBS lead (1.5 mm or 0.5 mm vertical electrode spacing) placed with segmented contact 2 at the ventral posterolateral “sensorimotor” region of the GPi. The effect of tissue heterogeneity was examined by replacing the MIDA tissues with a homogeneous tissue of conductance 0.3 S/m. DBS pulses (amplitude: 1 mA, pulse width: 60 μs, frequency: 130 Hz) were used to produce VTAs. The following DBS contact configurations were tested: single-segment monopole (2B-/Case+), two-segment monopole (2A-/2B-/Case+ and 2B-/3B-/Case+), ring monopole (2A-/2B-/2C-/Case+), one-cathode three-anode bipole (2B-/3A+/3B+/3C+), three-cathode three-anode bipole (2A-/2B-/2C-/3A+/3B+/3C+). Additionally, certain vertical configurations were repeated with 2 mA current amplitude.Results: Using a heterogeneous tissue model affected both the size and shape of the VTA in GPi. Electrodes with both 0.5 mm and 1.5 mm vertical spacing (1 mA) modeling showed that the single segment monopolar VTA was entirely contained within the GPi when the active electrode is placed at the posterolateral “sensorimotor” GPi. Two segments in a same ring and ring settings, however, produced VTAs outside of the GPi border that spread into adjacent white matter pathways, e.g., optic tract and internal capsule. Both stacked monopolar settings and vertical bipolar settings allowed activation of structures dorsal to the GPi in addition to the GPi. Modeling of the stacked monopolar settings with the DBS lead with 0.5 mm vertical electrode spacing further restricted VTAs within the GPi, but the VTA volumes were smaller compared to the equivalent settings of 1.5 mm spacing.

研究目标：探究定向深部脑刺激（DBS）电极配置及其垂直电极间距对苍白球内侧（GPi）激活组织体积（VTA）的影响。研究背景：定向DBS电极导线可能使临床医生能够精确地将电流场定位到传统靶区内的不同功能网络。通过模拟不同单极或双极配置下VTA的形状和大小，可以为GPi DBS的临床编程策略提供信息。然而，许多VTA的计算模型受限于假设组织均匀性。研究方法：本研究构建了一个包含定向DBS导线的多模态图像基础详细解剖（MIDA）计算模型，电极间距分别为1.5毫米或0.5毫米，并将分段接触2放置于GPi的腹侧后外侧“感觉运动”区域。通过将MIDA组织替换为导电率为0.3 S/m的均匀组织，考察了组织异质性的影响。使用DBS脉冲（幅度：1 mA，脉冲宽度：60 μs，频率：130 Hz）产生VTA。测试了以下DBS接触配置：单段单极（2B-/Case+）、双段单极（2A-/2B-/Case+和2B-/3B-/Case+）、环形单极（2A-/2B-/2C-/Case+）、一阴极三阳极双极（2B-/3A+/3B+/3C+）、三阴极三阳极双极（2A-/2B-/2C-/3A+/3B+/3C+）。此外，某些垂直配置在2 mA电流幅度下重复测试。研究结果：使用异质组织模型影响了GPi中VTA的大小和形状。电极间距为0.5毫米和1.5毫米的模型显示，当活动电极放置于GPi的背外侧“感觉运动”区域时，单段单极VTA完全包含在GPi内。然而，在同一环形和环形设置中的两段产生了超出GPi边界的VTA，并扩散至相邻的白质通路，例如视束和内囊。无论是叠加单极设置还是垂直双极设置，都允许激活GPi背侧的结构，除了GPi本身。使用0.5毫米垂直电极间距的DBS导线对叠加单极设置进行建模进一步限制了GPi内的VTA，但与1.5毫米间距的等效设置相比，VTA体积较小。