Augmented Reality and Robotic Systems for Assistance in Percutaneous Nephrolithotomy Procedures: Recent Advances and Future Perspectives

Percutaneous nephrolithotomy is the gold standard for the treatment of renal stones larger than 20 mm in diameter. The treatment outcomes of PCNL are highly dependent on the accuracy of the puncture step, in order to achieve a suitable renal access and reach the stone with a precise and direct path. Thus, performing the puncturing to get the renal access is the most crucial and challenging step of the procedure with the steepest learning curve. Many simulation methods and systems have been developed to help trainees achieve the requested competency level to achieve a suitable renal access. Simulators include human cadavers, animal tissues and virtual reality simulators to simulate human patients. On the other hand, the availability of pre-operative information (e.g., computed tomography or magnetic resonance imaging) and of intra-operative images (e.g., ultrasound images) has allowed the development of solutions involving augmented reality and robotic systems to assist the surgeon during the operation and to help a novel surgeon in strongly reducing the learning curve. In this context, the real-time awareness of the 3D position and orientation of the considered anatomical structures with reference to a common frame is fundamental. Such information must be accurately estimated by means of specific tracking systems that allow the reconstruction of the motion of the probe and of the tool. This review paper presents a survey on the leading literature on augmented reality and robotic assistance for PCNL, with a focus on existing methods for tracking the motion of the ultrasound probe and of the surgical needle