The Robotic System for the Treatment of Locally Advanced Cervical Cancer with Stereotactic Body Radiotherapy Boost: Results of a Phantom-Based and Preliminary Study

Abstract

To fix uterocervical position, compensate uterocervical intrafraction motion, and thus improve the accuracy of dose delivery based on the robotic system for the treatment of locally advanced cervical cancer with stereotactic body radiotherapy boost. CT images were acquired after robot arm implanted a fixator with fiducial markers into the cervix of pelvic phantom. The treatment plans were designed by contoured a simulated tumor lesion site. The fiducial markers position was obtained by real-time image guidance system and was registered with digitally reconstructed radiographs to calculate correlation error of six directions. The correlation error was delivered to the robotic arm to precisely adjust the position and posture of the fixator, and thus compensated uterocervical intrafraction movement through the interactive interface of the robotic system. The pressure sensor at the head of the fixator provided real-time feedback on the pressure value at the contact surface between the fixer and the cervix. The correlation error of six directions and the pressure value were extracted and analyzed from the log file. The data from the log file indicated that the three translational direction correlation error of x, y and z were 0.19mm, 0.20mm and 0.10mm, respectively. The three rotational direction correlation error of roll, pitch and yaw were 0.25°, 0.21° and 0.23°, respectively. With the increase of the relative distance between cervix and pressure sensor, the mean value of pressure variation decreases gradually. When the relative distance is 0.5mm and 3mm, the mean value of pressure variation is approximately 76% and 32%, respectively. The correlation accuracy of the robotic system meets the clinical requirements. The robot arm can fix and monitor the cervical motion in real time during radiotherapy. The robot system adjusts the position of the fixator to correct the uterocervical intrafraction motion error, which is feasible and has good clinical application prospect.