Development of a tendon driven robotic probe for prostate palpation

Palpation is a clinical diagnosis method utilized by physicians to acquire valuable information about the pathological condition of an organ using the sense of touch. This method, however, is subjective. The accuracy depends on the physician's experience and skill. Therefore, to make palpation objective and minimize variability in prostate cancer diagnosis among physicians, an automated palpation system is required. This paper describes the design and experimental evaluation of a 2 Degrees of Freedom (2DoF) tendon driven robotic palpation probe. The probe's palpation motion is controlled by actuating driving tendons using a cable-differential pulley transmission system and a return spring. A kinematic model of the robotic probe was derived. Furthermore, a tendon path length model was geometrically determined, and an optimization method for guide arc center placement to minimize change in tendon length was presented. Preliminary experimental and theoretical results were compared to determine the positioning accuracy. The difference between theoretical pitch angles [0°,80°] and measured values for the yaw angle range of [0°, 40°] was found to be in the range of 0.03° ~ 5.06°.Clinical Relevance- Diagnosis based on manual palpation is often subjective and palpation sensitivity depends on the physician's level of experience and skill. Therefore, an objective method for acquiring tactile information is relevant. Robotic palpation system provides objective and quantitative information for better understanding of the pathological and physiological changes in the tissue using mechanical properties as biomarkers.