Ataollahi Asghar, Karim Rashed, Fallah Arash Soleiman, Rhode Kawal, Razavi Reza, Seneviratne Lakmal D, Schaeffter Tobias, Althoefer Kaspar
IEEE Trans Biomed Eng. 2016 Nov;63(11):2425-2435. doi: 10.1109/TBME.2013.2276739. Epub 2013 Aug 6.
This paper presents a novel MR-compatible 3-DOF cardiac catheter steering mechanism. The catheter's steerable structure is tendon driven and consists of miniature deflectable, helical segments created by a precise rapid prototyping technique. The created catheter prototype has an outer diameter of 9 Fr (3 mm) and a steerable distal end that can be deflected in a 3-D space via four braided high-tensile Spectra fiber tendons. Any longitudinal twist commonly observed in helical structures is compensated for by employing clockwise (CW) and counter clockwise (CCW) helical segments in an alternating fashion. A 280 μm flexible carbon fiber rod is used as a backbone in a central channel to improve the structure's steering and positioning repeatability. In addition to the backbone, a carbon fiber tube can be inserted into the structure to a varying amount capable of changing the structure's forcibility and, thus, providing a means to change the curvature and to modify the deflectable length of the catheter leading to an extension of reachable points in the catheter-tip workspace. A unique feature of this helical segment structure is that the stiffness can be further adjusted by appropriately tensioning tendons simultaneously. An experimental study has been conducted examining the catheter-tip trajectory in a 3-D space and its positioning repeatability using a 5-DOF magnetic coil tracking system. Furthermore, MRI experiments in a 1.5-T scanner confirmed the MR-compatibility of the catheter prototype. The study shows that the proposed concept for catheter steering has great potential to be employed for robotically steered and MR-guided cardiac catheterization.
本文提出了一种新型的与磁共振兼容的三自由度心脏导管转向机构。该导管的可转向结构由肌腱驱动，由精密快速成型技术制造的微型可偏转螺旋段组成。所制造的导管原型外径为9 Fr（3毫米），其可转向远端可通过四根编织的高强度光谱纤维肌腱在三维空间中偏转。通过交替采用顺时针（CW）和逆时针（CCW）螺旋段，可补偿螺旋结构中常见的任何纵向扭曲。一根280μm的柔性碳纤维杆用作中心通道的主干，以提高结构的转向和定位重复性。除了主干外，还可将碳纤维管以不同的量插入结构中，从而能够改变结构的可操纵性，进而提供一种改变导管曲率和可偏转长度的方法，使导管尖端工作空间中可到达的点得以扩展。这种螺旋段结构的一个独特之处在于，可通过同时适当张紧肌腱来进一步调整刚度。利用五自由度磁线圈跟踪系统进行了一项实验研究，以检测导管尖端在三维空间中的轨迹及其定位重复性。此外，在1.5-T扫描仪中进行的磁共振成像实验证实了导管原型与磁共振的兼容性。研究表明，所提出的导管转向概念在机器人辅助和磁共振引导的心脏导管插入术中具有很大的应用潜力。
