Accuracy of Touch-Based Registration During Robotic, Image-Guided Partial Nephrectomy Before and After Tumor Resection in Validated Phantoms.

Aim Image guided surgery (IGS) allows for accurate, real-time localization of sub-surface critical structures during surgery. No prior IGS systems have described a feasible method of intraoperative re-registration after manipulation of the kidney during robotic partial nephrectomy (PN). We present a method for seamless re-registration during IGS and evaluate accuracy before and after tumor resection in two validated kidney phantoms. Methods We performed robotic PN on two validated kidney phantoms- one with an endophytic tumor and one with an exophytic tumor- with our IGS system utilizing the da Vinci Xi robot. Intraoperatively, the kidney phantoms' surfaces were digitized with the da Vinci robotic manipulator via a touch-based method and registered to a 3D segmented model created from cross-sectional CT imaging of the phantoms. Fiducial points were marked with a surgical marking pen and identified after the initial registration using the robotic manipulator. Segmented images were displayed via picture-in-picture in the surgeon console as tumor resection was performed. After resection, re-registration was performed by re-identifying the fiducial points. The accuracy of the initial registration and re-registration was compared. Results The root mean square (RMS) averages of target registration error (TRE) were 2.53mm and 4.88mm for the endophytic and exophytic phantoms, respectively. IGS enabled resection along pre-planned contours. Specifically, the RMS averages of the normal TRE over the entire resection surface were 0.75mm and 2.15mm for the endophytic and exophytic phantoms respectively. Tumors were resected with negative margins. Point-based re-registration enabled instantaneous re-registration with minimal impact on TRE compared to the initial registration (from 1.34mm to 1.70mm pre-resection and 1.60mm to 2.10mm post-resection). Conclusions We present a novel and accurate registration and re-registration framework for use during IGS for PN with the da Vinci Xi surgical system. The technology is easily integrated into the surgical workflow and does not require additional hardware.