A 3-axis optical force/torque sensor for prostate needle placement in Magnetic resonance imaging environments

The work presented in this paper has been performed in furtherance of developing an MRI (Magnetic resonance imaging) compatible fiber optical force sensor. In this paper, we discuss the design criteria and sensing principle of this optical sensor for monitoring forces in the 0-20 Newton range with an sub-Newton resolution. This instrumentation enables two degrees-of-freedom (DOF) torque measurement and one DOF force measurement. A novel flexure mechanism is designed and the finite element analysis is performed to aid the optimization of the design parameters. This 3 axis force/torque sensor with this range and resolution is an ideal tool for interventional procedures, e.g. needle biopsy and brachytherapy. The sensor is experimentally investigated and calibrated. Calibration results demonstrate that this sensor is a practical and accurate measurement apparatus.