Enhancing haptic feedback of subsurfaces during needle insertion

Haptic feedback can be helpful for accurate needle insertion but is complicated by friction on the needle shaft. Concepts to directly measure the forces at the needle tip exist but cause additional cost and complexity. Moreover, haptic devices may show inaccuracies in recreating forces. We present a novel force feedback method that uses needle shaft forces and enhances haptic feedback of subsurfaces based on robotic ultrasound elastography. This approach allows to overcome accuracy limitations of haptic devices. We evaluate our method in a volunteer subject study using recordings from a robotic needle driver setup. We compare haptic feedback based on shaft and enhanced force for the detection of surfaces inside of gelatin phantoms. Using our method, the error of subsurface detection decreased from more than 16 to about 1.7 mm for the first subsurface. A second subsurface was solely detectable using our method with an error of only 1.4 mm. Insertion time decreased by more than 32%. The results indicate that our enhanced sensor is suitable to detect subsurfaces for untrained subjects using a haptic feedback device of limited accuracy.