Azizi Arash, Tremblay Charles C, Gagné Kévin, Martel Sylvain
Nanorobotics Laboratory, Department of Computer and Software Engineering, Institute of Biomedical Engineering, Polytechnique Montréal, Montréal, QC, Canada.
Sci Robot. 2019 Nov 27;4(36). doi: 10.1126/scirobotics.aax7342.
Navigating tethered instruments through the vasculatures to reach deeper physiological locations presently inaccessible would extend the applicability of many medical interventions, including but not limited to local diagnostics, imaging, and therapies. Navigation through narrower vessels requires minimizing the diameter of the instrument, resulting in a decrease of its stiffness until steerability becomes unpractical, while pushing the instrument at the insertion site to counteract the friction forces from the vessel walls caused by the bending of the instrument. To reach beyond the limit of using a pushing force alone, we report a method relying on a complementary directional pulling force at the tip created by gradients resulting from the magnetic fringe field emanating outside a clinical magnetic resonance imaging (MRI) scanner. The pulling force resulting from gradients exceeding 2 tesla per meter in a space that supports human-scale interventions allows the use of smaller magnets, such as the deformable spring as described here, at the tip of the instrument. Directional forces are achieved by robotically positioning the patient at predetermined successive locations inside the fringe field, a method that we refer to as fringe field navigation (FFN). We show through in vitro and in vivo experiments that x-ray-guided FFN could navigate microguidewires through complex vasculatures well beyond the limit of manual procedures and existing magnetic platforms. Our approach facilitated miniaturization of the instrument by replacing the torque from a relatively weak magnetic field with a configuration designed to exploit the superconducting magnet-based directional forces available in clinical MRI rooms.
将束缚式器械在脉管系统中导航至目前难以到达的更深生理位置，将扩展许多医学干预的适用性，包括但不限于局部诊断、成像和治疗。在更狭窄的血管中导航需要将器械直径最小化，这会导致其刚度降低，直至可操纵性变得不切实际，同时在插入部位推动器械以抵消器械弯曲引起的来自血管壁的摩擦力。为了突破仅使用推力的限制，我们报告了一种方法，该方法依赖于由临床磁共振成像（MRI）扫描仪外部发出的磁边缘场产生的梯度在尖端产生的互补定向拉力。在支持人体尺度干预的空间中，每米超过2特斯拉的梯度产生的拉力允许在器械尖端使用较小的磁体，例如此处所述的可变形弹簧。通过将患者机器人定位在边缘场中的预定连续位置来实现定向力，我们将这种方法称为边缘场导航（FFN）。我们通过体外和体内实验表明，X射线引导的FFN可以使微导丝在复杂脉管系统中导航，远超手动操作和现有磁性平台的极限。我们的方法通过用一种设计用于利用临床MRI室中基于超导磁体的定向力的配置来替代相对较弱磁场的扭矩，促进了器械的小型化。
