ABSTRACT
Despite the success and prospects of the robotic catheter system for the cardiovascular access, loss of vision, and haptics have limited its global adoption. A direct implication is the great difficulty posed when trying to eliminate the backlash in catheters during vascular cannulations. As a result, physicians and patients end up been exposed to high radiation for a long period of time. Existing control systems proposed for such interventional robots have not fully consider the hysteretic (backlash) behavior. In this study, a novel robotic catheter system is designed for accessing the human cardiac area through the radial vasculature, while single factor descriptive analysis is employed to characterize the backlash behavior during axial motions of the interventional robot. Based on the descriptive analysis, an adaptive system is proposed for the backlash compensation during the cardiovascular access. The adaptive system consists of a neuro-fuzzy module that predicts a backlash gap based on bounded motion signals, and contact force modulated from a modified error-based force control model. The proposed system is implemented in MATLAB and visual C++. Finally, an in vitro experiment with a human tubular model, shows that the proposed adaptive compensation system can minimize the backlash occurrence during cardiovascular access.
Subject(s)
Catheters , Robotic Surgical Procedures/methods , Equipment Design/methods , HumansABSTRACT
BACKGROUND: Implantation of nonabsorbable polypropylene (PP) mesh in the vagina is the main surgical treatment for pelvic organ prolapse (POP); however, clinical outcomes remain controversial and far from satisfactory. In particular, reducing the exposure or erosion of vaginal implants to obtain improved functional reconstruction is challenging. There is an urgent need for the development of new materials and/or products for POP treatment. A nanofibrous biomimetic mesh was recently developed to address this issue. OBJECTIVE: In this study, the basic properties of the newly developed mesh, including structural characteristics, mechanical properties, biological response of human umbilical cord mesenchymal stem cells in vitro, and tissue regeneration and biocompatibility in vivo, were evaluated and compared with those of Gynemesh™PS. METHODS: Scanning electron microscopy and uniaxial tensile methods were used to evaluate microstructure and mechanical properties, respectively. Mesenchymal stem cell growth on the meshes was observed by fluorescence microscopy to visualize the expression of enhanced red fluorescent protein. Twenty-four mature female Sprague Dawley rats were randomly assigned to two groups: group 1 (nanofibrous biomimetic mesh, Medprin, Germany, n=12) and group 2 (Gynemesh(TM)PS, Ethicon, USA; n=12). The posterior vaginal wall was incised from the introitus, and the mesh was then implanted. Three implants of each type were tested for 1, 4, 8 and 12 weeks. Connective tissue organization, inflammation, vascularization, and regenerated tissue were histologically assessed. RESULTS: The nanofibrous biomimetic mesh is a relatively heavy material and exhibited lower porosity than Gynemesh(TM)PS. The new mesh was stiffer than Gynemesh(TM)PS (p<0.001) but supported human umbilical cord mesenchymal stem cell attachment. Erosion of the grafts did not occur in any animal. The nanofibrous biomimetic mesh was encapsulated by a thicker layer of connective tissue and was associated with significantly greater inflammatory scores compared with Gynemesh(TM)PS. At 12 weeks, the vascularization of the new mesh was greater than that of Gynemesh(TM)PS (p<0.05). No significant difference in the thickness of the smooth muscle layer following implantation was observed between the two groups (p>0.05). CONCLUSIONS: The nanofibrous biomimetic mesh is a candidate for reinforcing pelvic reconstruction. The mesh could be improved by decreasing its weight and stiffness and increasing its porosity. This mesh could serve as a carrier for stem cells in future regenerative medicine and tissue engineering research.
