Research On Navigation Methods Of Robot-assisted Flexible Needle Puncture System

Minimally invasive treatment technology as a new medical technology is developing rapidly in recent years for living tissue pathology, directed drugs delivery in some organs. Needle insertion is perhaps the most widely used technique in these surgeries. However, the rigid needle in the traditional surgery can only be punctured straightly. Therefore many complex surgeries can’t be implemented.A special nickel-titanium alloy bevel needle is adopted in this thesis. This type of flexible needle with sufficient flexibility can bend and generate arc trajectory, due to the lateral force of tissue on the needle bevel. So, the needle can avoid some sensitive obstacles (nerve, vein, bones and other vital organs) and reach the target accurately. This thesis proposed flexible needle visual positioning methods and the flexible needle dynamics modeling as well as path planning methods. The main contents include the following aspects:Firstly, the apparatus and imaging properties of two imaging devices, binocular vision and C-arm X-ray, are studied. Furthermore, relative calibration references are designed and the calibration of the imaging system is completed based on the linear camera model. In addition, the position of needle tip is detected by image feature point detection technology.Secondly, the flexible needle body coordinate system and the world coordinate system are proposed based on the characteristics of flexible needle trajectory, and transformation matrix between two coordinate systems is deduced as well. An improved kinematic model with rebound is proposed to describe the trajectory characteristics of flexible needle, which is obtained by experiment data and error analysis. Results of puncture tests verify the validity of the improved model.Thirdly, flexible needle path planning with dynamic programming algorithm is established to solve the key issues of the flexible needle path planning with kinematic constraints. Combining appropriate work space discretization with puncture strategy discretization, flexible needle autonomous path planning is achieved. In order to solve the impact of obstacles on the path planning, author proposed the concept of fuzzy obstacle, which not only avoids hitting obstacles, but also optimizes the path. The simulation results show the validity of the proposed path planning algorithm.Finally, the results of the dissertation are summarized based on puncture experiments meanwhile further research topics are pointed out.