Preliminary Evaluation of an Online Estimation Method for Organ Geometry and Tissue Stiffness

During open surgeries, surgeons use tactile palpation to form an understanding of the anatomy, including any underlying anatomical structures such as arteries or tumors. This letter explores methods for restoring this capability in the context of minimally invasive robot-assisted surgery. Previous works have demonstrated the ability of robots to use discrete palpation to characterize organ shape and, when followed with offline data processing, to produce a stiffness map of the organ. In our earlier work, we presented an offline estimation technique, independent of palpation strategy, to estimate organ shape and stiffness using Gaussian processes. This study extends our prior work by demonstrating a fast online technique for estimation of organ shape and stiffness. Our goal is to provide near video-frame-rate updates of the organ geometry and tissue stiffness during force controlled exploration. Two different palpation modes are experimentally explored: autonomous palpation and constrained semiautonomous teleoperation. We report the experimental evaluation of our approach for stiffness estimation using autonomous palpation. And we demonstrate the feasibility of using our method during interactive teleoperation in a simulated surgical scenario. We believe that future use of the online stiffness and geometry information based on our proposed method can help surgeons in improving their understanding of the surgical scene and its correlation to preoperative imaging, thereby increasing safety and improving surgical outcomes.