Studies On Application Of Navigation And Robot Technology In Percutaneous Ultrasound-Guided Liver Tumor Ablation

Percutaneous ultrasound-guided thermal ablation has been developed as a effective minimally-invasive treatment for liver tumor in the last decade. Accurate deployment of the ablation needle is crucial to ensure complete necrosis of the tumor. Currently, placement of ablation needle is highly dependent on operator experience such as spatial targeting ability. Improper deployment of ablation needles often leads to residual tumor. We developed a robotic system based on electromagnetic tracking to facilitate more accurate placement of the needle.In this dissertation we first analyze the human factors influencing the accuracy for implanting ablation needles. The spatial targeting ability of the operator was assessed in agar ball model. Results showed puncture of target with distinct image hints such as the ball center can be accurate in experienced hands (with an error of approximately 3mm), while puncture of target without distinct hints are often inaccurate, the three edges of the triangle formed by the tips when implanting multiple needles differ greatly in length, adjuvant techniques are needed to improve the accuracy of needle placement.Based upon results of the above study, we present the underlying theory for the navigation and robot system and draw up the plan for the robotic system used for guiding placement of ablation needles. Three major parts of the robotic system—3D ultrasound, electromagnetic tracking software, robot, were developed and registered together. The robot adopted the design of a SCARA arm and a RCM wrist. Tests taken in tank and ex vivo bovine livers showed the robotic system had a high precision in deploying ablation needles (with an error of within 0.95mm), robot combined with navigation was more accurate than navigation alone in deploying multiple ablation needles, which can reliably obtain desirable thermal field to envelop the tumor model.After experiments in ex vivo livers, we tested the precision of the robotic system in anesthetized swines. Due to the influence of respiration, the error was greater (4.48±0.95mm). We presented suggestions for improvement of the display of the navigation software and the mechanical design of the robot.This study demonstrates navigation combined with robot technique is feasible to improve the precision of deploying ablation needles, future studies are warranted to optimize the system to meet requirements in clinical practice.