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Session: Advances in SRS/SBRT [Return to Session]

Positioning Accuracy of a Robotic Motion Head Platform for Real-Time 6DoF Robotic Motion-Compensated SRS

K Farrey1*, K Yenice2, P Ferjancic3, E Flores-Martinez4, R Wiersma5, C Denis6, J Kelly7, (1) University of Chicago, Chicago, IL, (2) University of Chicago, Chicago, IL, (3) University of Chicago, Chicago, IL, (4) University of Chicago Medical Center, Chicago, IL, (5) University of Pennsylvania, Philadelphia, PA, (6) Cdr Systems, ,,(7) Cdr Systems,


TU-B-202-5 (Tuesday, 7/12/2022) 8:30 AM - 9:30 AM [Eastern Time (GMT-4)]

Room 202

Purpose: To assess the positioning accuracy of a novel 6DoF robotic prototype commercial head platform for motion-compensated frameless stereotactic radiosurgery (SRS).

Methods: We used CBCT and surface imaging to assess the positioning accuracy of the 6DoF robotic platform. We entered known offsets with an anthropomorphic head phantom within the motion range of the robot and verified its position with a clinically implemented surface imaging system. We then confirmed positioning accuracy using CBCT and a vendor supplied QA head phantom with imbedded BBs at known locations to the robot software. We used 6DoF CBCT match results as input for the robotic platform corrections and then acquired a final CBCT to record the residual corrections. As the final step in validation of robotically-guided SRS delivery we did two end-to-end tests using a scintillator and Gafchromic film positioned in the anthropomorphic phantom and delivered a single-iso-two target SRS plan with the scintillator confirming the accuracy of the planned dose in the center of a target and the film confirming the position of the delivered dose distribution after robotic adjustments.

Results: Surface image tracking showed positioning accuracy of -0.04mm ±0.16mm and -0.02° ±0.08° degrees. Residual position and angular offsets of post correction CBCTs were 0.07mm ±0.16mm and 0.0° ±0.05°. Scintillator measurements showed the dose delivery of each target to be within 2.5% of the planned dose well within the accepted clinical criteria.

Conclusion: Our measurements show that the positioning accuracy of the platform is accurate within 0.08mm ±0.23mm and 0.02° ±0.09°. Dose delivery accuracy to the scintillator placed at the smallest 9mm target was within 2.5%. This robotic platform, when fully implemented, can potentially be used along with a surface imaging system in a real-time motion-compensated SRS approach with minimal patient immobilization.

Funding Support, Disclosures, and Conflict of Interest: The robotic platform used for this project was provided to our institution by CDR Systems.


Not Applicable / None Entered.


Not Applicable / None Entered.

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