Li Yan, Deng Jianxin, Zhou Jun, Li Xueen
Key Laboratory of High Efficiency and Clean Mechanical Manufacture of MOE, Department of Mechanical Engineering, Shandong University, Jinan, 250061, PR China.
Department of Neurosurgery, Qilu Hospital of Shandong University, Jinan, 250012, PR China.
J Mater Sci Mater Med. 2016 Nov;27(11):163. doi: 10.1007/s10856-016-5775-5. Epub 2016 Sep 19.
Corresponding to pre-puncture and post-puncture insertion, elastic and viscoelastic mechanical properties of brain tissues on the implanting trajectory of sub-thalamic nucleus stimulation are investigated, respectively. Elastic mechanical properties in pre-puncture are investigated through pre-puncture needle insertion experiments using whole porcine brains. A linear polynomial and a second order polynomial are fitted to the average insertion force in pre-puncture. The Young's modulus in pre-puncture is calculated from the slope of the two fittings. Viscoelastic mechanical properties of brain tissues in post-puncture insertion are investigated through indentation stress relaxation tests for six interested regions along a planned trajectory. A linear viscoelastic model with a Prony series approximation is fitted to the average load trace of each region using Boltzmann hereditary integral. Shear relaxation moduli of each region are calculated using the parameters of the Prony series approximation. The results show that, in pre-puncture insertion, needle force almost increases linearly with needle displacement. Both fitting lines can perfectly fit the average insertion force. The Young's moduli calculated from the slope of the two fittings are worthy of trust to model linearly or nonlinearly instantaneous elastic responses of brain tissues, respectively. In post-puncture insertion, both region and time significantly affect the viscoelastic behaviors. Six tested regions can be classified into three categories in stiffness. Shear relaxation moduli decay dramatically in short time scales but equilibrium is never truly achieved. The regional and temporal viscoelastic mechanical properties in post-puncture insertion are valuable for guiding probe insertion into each region on the implanting trajectory.
分别对应穿刺前和穿刺后植入过程，研究了丘脑底核刺激植入轨迹上脑组织的弹性和粘弹性力学特性。通过使用完整猪脑的穿刺前针插入实验研究穿刺前的弹性力学特性。将线性多项式和二阶多项式拟合到穿刺前的平均插入力。根据两个拟合的斜率计算穿刺前的杨氏模量。通过对沿计划轨迹的六个感兴趣区域进行压痕应力松弛测试，研究穿刺后植入过程中脑组织的粘弹性力学特性。使用玻尔兹曼遗传积分将具有 Prony 级数近似的线性粘弹性模型拟合到每个区域的平均载荷轨迹。使用 Prony 级数近似的参数计算每个区域的剪切松弛模量。结果表明，在穿刺前植入过程中，针力几乎随针位移线性增加。两条拟合线都能很好地拟合平均插入力。从两个拟合的斜率计算得到的杨氏模量分别值得信赖，可用于对脑组织的线性或非线性瞬时弹性响应进行建模。在穿刺后植入过程中，区域和时间都对粘弹性行为有显著影响。六个测试区域在刚度上可分为三类。剪切松弛模量在短时间尺度内急剧衰减，但从未真正达到平衡。穿刺后植入过程中的区域和时间粘弹性力学特性对于指导探针在植入轨迹上插入每个区域具有重要价值。
