Tip Design for Safety of Steerable Needles for Robot-Controlled Brain Insertion.
Tip Design for Safety of Steerable Needles for Robot-Controlled Brain Insertion.
复制标题
DOI：
10.2147/rsrr.s141085
复制
发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Riviere CN
中科院分区：
文献类型：
--
作者：
Lehocky CA;Fellows-Mayle W;Engh JA;Riviere CN
目前在神经外科针头插入的实践是由刚性探针固有的直线轨迹限制。一种允许曲线轨迹的技术涉及柔性斜头针，由于其不对称，在插入时弯曲。在大脑中，为了安全起见，需要避免实验室研究中经常使用的尖锐尖端，而采用更圆角的轮廓。另一方面，转向性能要求最大的不对称性。因此，设计安全的斜头脑针，需要通过调整针径、斜角和圆角（或针尖）半径来管理这种权衡，以达到适当的不对称设计，同时产生的应变、应变率和应力低于可能损害脑组织的水平。在同时插入和旋转的有限元模拟中，评估了不同针半径、斜角和圆角半径值的设计。脑组织模型为超弹性线性粘弹性材料。根据现有文献，采用0.19应变、10 s−1应变速率和120 kPa应力作为安全阈值。选择了针半径、斜角和圆角半径的安全值，以及安全操作的适当速度包络。在猪体内模型（N=3）的研究中，制作了由此产生的针，并与Sedan侧切脑活检针进行了比较。选取的原型针直径为1.66 mm，锥度为10°，圆角半径为0.25 mm。术后计算机断层扫描和组织学检查显示，原型针和色当针在组织损伤和出血方面没有差异。通过对应变、应变率和应力损伤阈值的比较，提出了一种安全斜头脑针的通用设计技术。这项技术的全部潜力有待于确定更精确的安全阈值。
Current practice in neurosurgical needle insertion is limited by the straight trajectories inherent in rigid probes. One technique allowing curvilinear trajectories involves flexible bevel-tipped needles, which bend during insertion because of their asymmetry. In the brain, safety will require avoidance of the sharp tips often used in laboratory studies, in favor of a more rounded profile. Steering performance, on the other hand, requires maximal asymmetry. Design of safe bevel-tipped brain needles, thus, involves management of this trade-off by adjusting needle gage, bevel angle, and fillet (or tip) radius to arrive at a design that is suitably asymmetrical while producing strain, strain rate, and stress below the levels that would damage brain tissue. Designs with a variety of values of needle radius, bevel angle, and fillet radius were evaluated in finite-element simulations of simultaneous insertion and rotation. Brain tissue was modeled as a hyperelastic, linear viscoelastic material. Based on the literature available, safety thresholds of 0.19 strain, 10 s−1 strain rate, and 120 kPa stress were used. Safe values of needle radius, bevel angle, and fillet radius were selected, along with an appropriate velocity envelope for safe operation. The resulting needle was fabricated and compared with a Sedan side-cutting brain biopsy needle in a study in the porcine model in vivo (N=3). The prototype needle selected was 1.66 mm in diameter, with a bevel angle of 10° and a fillet radius of 0.25 mm. Upon examination of postoperative computed tomography and histological images, no differences in tissue trauma or hemorrhage were noted between the prototype needle and the Sedan needle. The study indicates a general design technique for safe bevel-tipped brain needles based on the comparison with relevant damage thresholds for strain, strain rate, and stress. The full potential of the technique awaits the determination of more exact safety thresholds.