Enabling minimal invasive palpation in flexible robotic endoscopes

In open surgery, palpation allows surgeons to haptically examine the patient’s tissue with their fingers. Hereby, palpation relates the pose of the surgeon’s finger inside the wound and the finger’s indentation into the tissue to the experienced forces in all directions. In this way, the surgeon is able to experience differences in tissue stiffness. Despite being a well-recognized standard procedure in open surgery, palpation has so far been unavailable for Minimally Invasive Surgery (MIS). Thus, surgeons can only rely on endoscope vision. To overcome this drawback, we aim to restore haptic feedback and thus palpation in MIS. In this paper, we present an Encapsulated Force-sensing Device (EFD) that can be mounted on the tip of a flexible articulated robotic endoscope. The EFD houses a miniature tri-axial force sensor (TFS) together with an integrated camera mounted onto the EFD’s tip. In order to enable palpation, the forces at the endoscope’s tip have to be acquired together with the exact shape of the flexible articulated endoscope. Importantly, articulated endoscopes enable us to apply conventional kinematics and determine the endoscope’s shape, which is not possible in endoscopes based on continuum mechanics. In a test set-up, we investigated the accuracy of the force measurement provided by our EFD. For this investigation, the robotic structure was fixed in one predefined pose and the forces from our EFD were compared to forces measured by a commercial force/torque sensor. With this test set-up, we could verify the concept of palpation (force and position measurement), even for MIS.