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Use of a 6D Couch for Real-Time Full Translational and Rotational Head Motion Correction During Stereotactic Radiosurgery: A Feasibility Study

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X Liu

X Liu*, AH Belcher , Z Grelewicz , RD Wiersma , The University of Chicago, Chicago, IL


SU-E-J-5 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall

This work presents a methodology for correcting full translational and rotational head motion deviations during frameless image-guided stereotactic radiosurgery (SRS) procedures with a robotic 6D couch. The main objective is to design control algorithms which optimize the correction motion of a 6D couch when sub-millimeter/sub-degree accuracy requirements are necessary in SRS.

The system includes 6D position tracking and a 6D couch with three serially connected platforms. The bottom platform controls yaw compensation (around the z axis), the middle one generates full 3D translational motion, and the top platform controls both pitch (around X) and roll (around Y) motion with two linear actuators. Based on the 6D position of the head and the couch at each moment, the desired 6D couch position for correction is calculated, with the required 6 actuator outputs computed by an inverse algorithm accordingly. To minimize their responsive motion, the actuators take action only after the head position deviates beyond certain predetermined thresholds, and for each action the head is returned to the center of desired 6D treatment position.

With computer simulation, head motion of an SRS patient was modeled and the simulated couch was used to compensate for this motion in real-time. For a 15-minute test with a 0.3 mm and 0.15 degree target position tolerance, the corrected 6D head position was within tolerance over 99.5% of the time. The actuators moved approximately 80 times during the simulation, and the total actuator motion for translational correction was around 205 mm.

We investigated a control approach for full translational and rotational head motion correction with a 6D couch. The simulations demonstrated that with moderate correction motion of a 6D couch, the control performance meets real-time sub-millimeter and sub-degree accuracy requirement of frameless SRS.

Funding Support, Disclosures, and Conflict of Interest: The research is funded by the American Cancer Society (ACS) grant. The grant name is: Frameless SRS Based on Robotic Head Motion Cancellation. The grant number is: RSG-13-313-01-CCE

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