Haptic system design for MRI-guided needle based prostate brachytherapy

This paper presents the design of a haptic system for prostate needle brachytherapy under magnetic resonance imaging (MRI) guidance. This haptic system consists of some recently developed MRI-compatible mechatronic devices, including a fiber optic force sensor and a piezoelectric motor actuated needle driver mounted on a specifically designed 3-axis linear stage. We first propose the teleoperation framework with system architecture, infrastructure and control algorithm for the master-slave haptic interface. Then we introduce some novel sensors and actuators for MRI-compatible mechatronic devices of this haptic system. We developed the force sensor which provides in-vivo measurement of needle insertion forces to render proprioception associated with the brachytherapy procedure. We discuss the sensing principle of the optical sensor which enables two degrees-of-freedom (DOF) torque measurement and one DOF force measurement. The second apparatus of this system is a high precision 3-axis linear stage actuated by piezoelectric motors and position sensed by optical linear and rotary encoders and all of them have proved good magnetic compatibility. The needle driver can simultaneously provide needle cannula rotation and stylet translation motion while the cannula translation is engendered by the stage. The independent rotation and translation motion of the cannula and stylet can increase the targeting accuracy while minimize the tissue deformation and damage. The master-slave haptic system is capable of positioning needle and sensing insertion forces thus increasing the operation autonomy, accuracy and reducing the operation time.