Surgical scene understanding in Robot-assisted Minimally Invasive Surgery (RMIS) is highly reliant on visual cues and lacks tactile perception. Force-modulated surgical palpation with tactile feedback is necessary for localization, geometry/depth estimation, and dexterous exploration of abnormal stiff inclusions in subsurface tissue layers. Prior works explored surface-level tissue abnormalities or single layered tissue-tumor embeddings with more than 300 palpations for dense 2D stiffness mapping. Our approach focuses on 3D reconstructions of sub-dermal tumor surface profiles in multi-layered tissue (skin-fat-muscle) using a visually-guided novel tactile navigation policy. A robotic palpation probe with tri-axial force sensing was leveraged for tactile exploration of the phantom. From a surface mesh of the surgical region initialized from a depth camera, the policy explores a surgeon's region of interest through palpation, sampled from bayesian optimization. Each palpation includes contour following using a contact-safe impedance controller to trace the sub-dermal tumor geometry, until the underlying tumor-tissue boundary is reached. Projections of these contour following palpation trajectories allows 3D reconstruction of the subdermal tumor surface profile in less than 100 palpations. Our approach generates high-fidelity 3D surface reconstructions of rigid tumor embeddings in tissue layers with isotropic elasticities, although soft tumor geometries are yet to be explored.

翻译：在机器人辅助微创手术（RMIS）中，手术场景理解高度依赖视觉线索，缺乏触觉感知。为实现异常硬质包埋物在皮下组织层中的定位、几何/深度估计及灵巧探查，具备触觉反馈的力调制手术触诊至关重要。先前研究主要探索表层组织异常或单层组织-肿瘤包埋，需进行超过300次触诊以生成密集的二维刚度图谱。本研究采用视觉引导的新型触觉导航策略，聚焦于多层组织（皮肤-脂肪-肌肉）中皮下肿瘤表面轮廓的三维重建。利用配备三轴力传感的机器人触诊探头对仿体进行触觉探查。基于深度相机初始化的手术区域表面网格，该策略通过从贝叶斯优化采样的触诊方式探查外科医生关注的区域。每次触诊均包含采用接触安全阻抗控制器进行的轮廓跟踪，以描绘皮下肿瘤几何形态，直至触及下层肿瘤-组织边界。通过对这些轮廓跟踪触诊轨迹进行投影，可在少于100次触诊的情况下实现皮下肿瘤表面轮廓的三维重建。本方法能够在各向同性弹性组织层中对刚性肿瘤包埋物生成高保真度的三维表面重建，但柔性肿瘤几何形态仍有待探索。