Master-Thesis Development of a Surgical Assistant System for Needle Adjustment in Prostate Brachytherapy

Title of the Master-Thesis Development of a Surgical Assistant System for Needle Adjustment in Prostate Brachytherapy Author: 1. Examiner: 2. Examiner: Semester: Thomas Lehmann Prof. Dr.-Ing. Bernhard Vondenbusch, Hochschule Furtwangen University Mahdi Tavakoli, PhD, University of Alberta BME 3 Abstract: The prototype of a robotic surgical assistant system was developed for prostate brachytherapy. Prostate brachytherapy is an effective, patient friendly and minimally-invasive cancer treatment procedure. The needles, which are used in this procedure, deflect from the intended path due to their bevelled tip. This deflection leads to a negative influence on the treatment efficiency and should therefore be minimized. The developed system is the prototype of an intelligent, 2-DOF surgical assistant tool. The main purpose of the system is the prediction and correction of needle tip deflection during the procedure. In order to estimate the needle deflection in real-time, a force sensor based virtual sensor was developed. The force sensor measures forces and moments at the needle base. The measured force/moment data is used by a mathematical model, which is based on mechanical needle properties. The model estimates the tip deflection of the needle in real-time during insertion into soft tissue. The assistant is therefore able to detect increasing deflection and carry out corrective measures in real-time. The used method for deflection correction is turning the needle about 180◦ when a predetermined threshold is exceeded in order to reverse the effect of the bevel and bring the needle back to its desired path. The prototype of a robotic surgical assistant system was developed for prostate brachytherapy. Prostate brachytherapy is an effective, patient friendly and minimally-invasive cancer treatment procedure. The needles, which are used in this procedure, deflect from the intended path due to their bevelled tip. This deflection leads to a negative influence on the treatment efficiency and should therefore be minimized. The developed system is the prototype of an intelligent, 2-DOF surgical assistant tool. The main purpose of the system is the prediction and correction of needle tip deflection during the procedure. In order to estimate the needle deflection in real-time, a force sensor based virtual sensor was developed. The force sensor measures forces and moments at the needle base. The measured force/moment data is used by a mathematical model, which is based on mechanical needle properties. The model estimates the tip deflection of the needle in real-time during insertion into soft tissue. The assistant is therefore able to detect increasing deflection and carry out corrective measures in real-time. The used method for deflection correction is turning the needle about 180◦ when a predetermined threshold is exceeded in order to reverse the effect of the bevel and bring the needle back to its desired path.