In the recent years research about robots assisting in needle insertion, ablation and surgeries is being produced constantly. Because of this there are quite a lot of needle insertion robot prototypes with some being commercially available as well. However, all the available robots differ from each other in terms of reasons why they are built, how they are used and the material they are built with. In this assignment a needle guidance robot designed for Irreversible Electroporation (IRE) will be used. Another reason why this robot differs from other available ones is the fact that is designed with MRI compatibility in mind and ability to use multiple parallel electrodes for electroporation.
There are obvious limitations when working with an MRI compatible robot since conventional materials cannot be used when building the robot. At the moment the current prototype has already been built using MRI compatible materials. The current prototype has 4 degrees of freedom, two translations and two rotations and can be seen in figure 1. The decision to have pneumatic actuation has already been made as well. The motors used are stepper motors designed at the University of Twente.
This assignment will be focusing on some of the next steps to create a functional prototype while also elaborating on a particular research topic. The full setup needs to be built and the needle positioning needs to be achieved. Thus a controller needs to be implemented in order to be able to position the needles. To design this framework the robotics middleware ROS will be used as it provides many packages that ease the implementation. For such a framework to be properly implemented sensory feedback needs to be available to be able to read the state of the robot and the needle. However, when designing for MRI compatibility choosing the right materials and actuators isn’t the only limitation. What sensors can be used in an MRI environment is also a big concern. Because of this and the scarcity of MRI compatible sensors a different method will be explored in achieving such feedback, that of acquiring this information through visual feedback/imaging. In these first tests conventional cameras and physical trackers will be used instead of MRI images because of time constraints. The accuracy and reliability of such a setup will be tested and analyzed, as well as how this changed when more needles are added. The available methodologies for tracking and location of the needle will also be explored.
However, certain questions still arise as to: How accurate, reliable and practical is it to use visual feedback/tracking as the main feedback for the needle position? What algorithms can be used to produce a higher accuracy? What methods can be implemented to account for loss of needle tracking information?
These questions and the implementation of a controller are the main focus of this assignment. The final goal is to be able to have a working prototype with which tests were conducted and the aforementioned questions were answered.