(Saturday, 4/7/2018)
Room: Foyer
Purpose: Stereotactic radiosurgery requires thorough review and evaluation of equipment before being clinically accepted for patient treatment. Linatech’s micro-MLC attachment allows for superior treatment by coupling 102 2mm thick leaves at isocenter, ten cones varying in size, and a positional dual camera all into one attachment. To ensure TG-54 requirements for stereotactic radiosurgery, Linatech’s micro-MLC attachment underwent an extensive evaluation to obtain clinically relevant information and develop QA practices that effectively evaluate alignment.
Methods: Beam profiles were measured for square field sizes 0.7cm through 12cm with depths ranging from 1.5 -20cm. All field sizes were measured with: TN60012 micro-diode, 0.0016cc pinpoint, and 0.004mm diamond chamber for 6MV. MLC positional accuracy was assessed with both picket fence and inverse picket fence tests. A Winston Lutz test in combination with a star pattern were created for reviewing tolerance during micro-MLC attachment and cone alignment at collimator angles 60, 120, 180, 240, 270, and 300 with gantry angles of 0, 90, 180, and 270. Patient plans were delivered and verified using PTW’s Octavius phantom and VeriSoft using a 3% and 3mm 3D gamma analysis with no optimization shifts. A 6 met plan was developed and delivered using SRS procedures to a 3D printed RTSafe gel phantom for final verification.
Results: MLC leakage was determined to be 1.6% and the penumbra was reduced by 2.67mm for a 6x6cm field with the attachment. Reattachment of the assembly demonstrated a tolerance of 0.23±0.22mm, leaves were found to be within a 0.1mm. Cone bank A was found to have a tolerance of 0.21±0.07mm while bank B had 0.35±0.09mm Three patient plans verified using PTW’s VeriSoft obtained gamma values of 96.8%, 97.1%, and 93.0%
Conclusion: The D2SRS micro-MLC attachment has fallen within expected specifications and the RTSafe has provided verification of the systems abilities for stereotactic radiosurgery.
Funding Support, Disclosures, and Conflict of Interest: Supported in part by CPRIT Training Grant (RP170345) Equipment tested was provided by the company Linatech
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