Author(s): Zhi, X. (2015)
Abstract:
Magnetic resonance imaging (MRI) compatible robotics is one of the new technologies for performing image guided minimally invasive interventions (MII) such as cancer biopsy gathering or brachytherapy. In this report, design, prototype, and test of a patient‐mounted image guided surgical robotic system for MII are reported. The technical requirements of the robot are determined based on a literate study regarding to different related products and experiences around the world. The robot consists of four degrees of freedom (DoF), making it able to orientate, insert, and rotate an axisymmetric surgical tool, such as a needle. With the patient-mounted method the robot compensates the patient’s motion passively and reduces three translation DoFs. To actuate the robot, an MRI compatible back‐drivable pneumatic step actuator is designed. The requirements of the actuator are determined based on a kinematic model of the robot. The actuator and remaining components of the robot are 3D printed and laser‐cut out of MRI compatible materials. To actuate the robot efficiently, five actuators are installed. Tests indicate that the actuator achieves a step motion of approximately 12°. With a lab-made DC motor based pneumatic distributor, a speed of approximately 1.25rad/s can be achieved. With the air pressure of 5bar, an output torque of approximately 125Nmm can be achieved. The speed can be increased by replacing the lab-made DC motor based pneumatic distributor with commercial valve terminal with higher frequency. The output torque can be increased by increasing the air pressure. The robot is able to penetrate its tool into a silicone gel based soft phantom. The insertion accuracy is roughly measured to be 2mm. With the lab-made DC motor based pneumatic distributor, a maximum insertion speed of the tool is roughly measured to be 11.6mm/s. Tests inside an MRI scanner indicate that the robot, including the actuator, is fully MRI compatible.
Document(s):
Zhi_MA_EEMCS.pdf