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Auto-Determination of the Dextrous WorkSpace in Robotic Stereotactic Radiosurgery

O Ogunmolu1*, X Liu2, R Wiersma3, (1) University of Pennsylvania, Philadelphia, PA, (2) University of Chicago, Chicago, IL, (3) University of Pennsylvania, Philadelphia, PA


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: Prior work has shown the feasibility of frameless and maskless patient head stabilization to be accurate to 0.5mm and 0.5deg precision using an optical feedback robot control of a patient’s 6 degree-of-freedom (6DoF) head motion in real-time. In the human cranium, the head-neck joint introduces a coupling that complicates independent control of motion axes. The positions and orientations of a robot’s legs needed for the manipulator’s reachable workspace for all head orientation set in SE(3) are limited by the hardware’s freedom and constraints. The robot’s dexterous workspace differs significantly for every patient given the variance in neck freedoms for different patient’s head anatomy. Here, we analyze the trajectories generated by the robot compensator as it manipulates the head within the robot’s dexterous workspace, ascertaining the suitability of robotic SRS motion compensation for a patient.

Methods: A parallel 6-DoF robot was positioned beneath a volunteer’s cranium. Head motion control trajectories were generated in LabVIEW (National Instruments, Austin TX) that move the patient’s cranium along predefined anterior-posterior (AP), superior-inferior (SI) and left-right (LR) translational motions in a mock motion correction. With infrared markers on the patient’s forehead, an optical camera measured the patient’s pose in real-time, which is then transformed to the robot’s frame using Kabsch’s algorithm.

Results: Preliminary results show the volunteer’s cranium achieved steady-state convergence along the LR and AP trajectories. However, we observe coupled motions along the SI axis that interfere with these pure translations. This may be associated with the human neck’s natural constraints; we thus conjecture that an additional mechanism’s freedom may resolve this.

Conclusion: We show the feasibility of real-time motion correction with a compact parallel robotic SRS platform. Future work will incorporate a decoupler for the nonlinearities that interfere with the presented pure translations.

Funding Support, Disclosures, and Conflict of Interest: The research reported in this publication was supported by National Cancer Institute of the National Institutes of Health under award number R01CA227124.


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