[Accuracy analysis of robotic assistant needle placement for lateral skull base biopsy].

Objective: To evaluate the accuracy and feasibility of a custom robot system guided by navigation for lateral skull base tumor biopsy. Methods: Two cadaver heads were used, with iopamidol injected into different areas in the skull base and infratemporal region to imitate the tumor. Cone beam CT (CBCT) scanning was performed before operation. With image data transferred to the graphical user interface of the computer workstation, the "tumor" was segmented as the target. The needle trajectory was determined by selecting the skin entry point and the target point on the surgical planning software. Following point-based registration, the data was sent to the robot control unit. The needle was automatically inserted into the intended target by the robot guided by optical navigation. After the procedure was performed, the instantaneous data of needle tip position acquired by navigation system was sent back to the computer workstation for accuracy verification. Subsequently, after the needle was released, CBCT scanning was performed again, and the pre-and post-operative skull were superimposed. The position data of needle tip was acquired on the postoperative image and the accuracy was re-verified. The paired t -test was used to compare the differences in the accuracy calculated by intraoperative navigation and postoperative image fusion. The independent samples t -test was used to compare the accuracy between the cadavers. The Pearson correlation coefficients ( r ) was used to analyze correlation between the needle intervention accuracy and insertion depth. Results: All 20 interventions were successfully performed. The mean deviation of the needle tip was (0.67±0.28) mm (measured by the navigation system) and (3.19±0.39) mm (measured by image fusion) respectively ( t= -23.238, P< 0.001). The comparison of accuracy test showed no significant difference between the cadavers ( t= -1.116, P= 0.279). Pearson correlation coefficients ( r= 0.714, P< 0.001) showed the close correlation between the needle intervention accuracy and insertion depth. The mean insertion depth was (5.14±0.21) cm. Conclusions: The experimental results show that the robot system is efficient and reliable. The navigation accuracy and the needle deflection are the most significant factors affecting robotic puncture procedures.