Display of needle tip contact forces for steering guidance

An MR-compatible biopsy needle stylet is instrumented with optical fibers that provide information about contact conditions between the needle tip and organs or hard tissues such as bone or tumors. This information is rendered via a haptic display that uses ultrasonic motors to convey directional cues to users. Lateral haptic cues at the fingertips improve the targeting accuracy and success rate in penetrating a prostate phantom. Although the original intent was for haptic cues to match the direction of contact forces and needle bending, more consistent results were obtained by using the cues as steering guidance (opposite to contact forces); accordingly this convention was adopted for the user experiments reported.