Abstract— This paper presents the first prototype of a
magnetic resonance imaging (MRI) compatible piezoelectric
actuated robot integrated with a high-resolution fiber optic
sensor for prostate brachytherapy with real-time in situ needle
steering capability in 3T MRI. The 6-degrees-of-freedom (DOF)
robot consists of a modular 3-DOF needle driver with fiducial
tracking frame and a 3-DOF actuated Cartesian stage. The
needle driver provides needle cannula rotation and translation
(2-DOF) and stylet translation (1-DOF). The driver mimics the
manual physician gesture by two point grasping. To render
proprioception associated with prostate interventions, a FabryPerot interferometer based fiber optic strain sensor is designed
to provide high-resolution axial needle insertion force measurement and is robust to large range of temperature variation. The
paper explains the robot mechanism, controller design, optical
modeling and opto-mechanical design of the force sensor. MRI
compatibility of the robot is evaluated under 3T MRI using
standard prostate imaging sequences and average signal noise
ratio (SNR) loss is limited to 2% during actuator motion. A
dynamic needle insertion is performed and bevel tip needle
steering capability is demonstrated under continuous real-time
MRI guidance, both with no visually identifiable interference
during robot motion. Fiber optic sensor calibration validates
the theoretical modeling with satisfactory sensing range and
resolution for prostate intervention.
Keywords: Optical Force Sensor, Fabry-Perot Interferometer,
MRI Compatibility, Needle Driver, Brachytherapy.