Feasibility of a novel technique using 3-dimensional modeling and augmented reality for access during percutaneous nephrolithotomy in two different ex-vivo models

Purpose: We describe a novel technique that uses mathematical calculation software, 3-dimensional (3D) modeling and augmented reality (AR) technology for access during percutaneous nephrolithotomy (PCNL) and report our first preliminary results in two different ex-vivo models. Methods: Novel software was created in order to calculate access point and angle by using pre-operative computed tomography (CT) obtained in 50 patients. Two scans, 27 s and 10 min after injection of contrast agent, were taken in prone PCNL position. By using DICOM objects, mathematical and software functions were developed to measure distance of stone from reference electrodes. Vectoral 3D modeling was performed to calculate the access point, direction angle and access angle. With specific programs and AR, 3D modeling was placed virtually onto real object, and the calculated access point and an access needle according to the calculated direction angle and access angle were displayed virtually on the object on the screen of tablet. Results: The system was tested on two different models—a stone placed in a gel cushion, and a stone inserted in a bovine kidney that was placed in a chicken—for twice, and correct access point and angle were achieved at every time. Accuracy of insertion of needle was checked by feeling crepitation on stone surface and observing tip of needle touching stone in a control CT scan. Conclusions: This novel device, which uses software-based mathematical calculation, 3D modeling and AR, seems to ensure a correct access point and angle for PCNL. Further research is required to test its accuracy and safety in humans.