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Session: Therapy General ePoster Viewing [Return to Session]

The Software Controller of Isocentric Rotation Chair Positioner for Treating Patients with Head/Neck Cancers in Fixed Carbon-Ion Beamline

W Hsi1*, X Zhang2, F Yang2, R Zhou2, (1) Univerisity Florida Health Proton Therapy Institute, Jacksonville, Florida, US (2) College of Physical Science and Technology, Sichuan University, Chengdu, Sichuan Province, China


PO-GePV-T-99 (Sunday, 7/25/2021)   [Eastern Time (GMT-4)]

Purpose: To utilize an isocentric rotating chair as a positioner for a clinical application, a software controller was built by implementing the mathematical manipulations of specific coordinate transformation to the IEC fixed (If) reference coordinate for each movement mechanism of chair.

Methods: A software controller to execute any required displacement under a treatment workflow was evaluated. The three major motion mechanisms in the chair positioner are a 360° rotating platform, a Hexapod, and a 3D translation module. To execute a 6 DoF displacement by the controller over the chair, the mathematical manipulations was developed in a matrix formula in the If coordinate through a proper transformation on each mechanism. The trend of deviations on the displacements between ideal and misaligned mechanism for each parameter was investigated and measured by using an optical tracking system. The tolerance of each parameter was investigated to achieve the accuracy of +/- 1.0 mm in translation and +/- 1.0° in rotation on any required displacement executed by the chair positioner.

Results: Developed mathematical manipulations in the matrix formula with measured deviations of parameters were integrated into a visual user interface. When a large deviation of 6 DoF displacement occurred due to misalignment of any mechanism that were reproducible in the Validation-and-Verification (VnV) procedure, the reproducible deviations were internally corrected in the Hexapod. A commissioning was conducted to meet clinical requirements after the VnV procedure. 17 patients was successfully treated by using this chair positioner.

Conclusion: The chair positioner using the software control with implemented mathematical manipulations was embedded to conduct a clinical trial under the workflow with an existing image-guided treatment system. The deformation of tilted posture on the Hexapod and/or the 3D platform will be further investigated as one of concern for using over 5° tilt fields.



    Patient Positioning, Image-guided Therapy, Radiation Therapy


    TH- External Beam- Particle/high LET therapy: Carbon ion therapy - instrumentation

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