(Saturday, 4/7/2018)
Room: Foyer
Purpose: To develop software that can programmatically analyze dosimetric images and reduce QA time when performing the Winston-Lutz test and to determine the isocenter wobble of the linear accelerator (Varian TrueBeam).
Methods: Dosimetric images of the Winston-Lutz test were acquired with a TrueBeam linear accelerator and loaded into a custom software application by use of the Eclipse Scripting Application Programming Interface (ESAPI) for Portal Dosimetry. The software application will allow the user to determine the center of the cone and ball to determine the coincidence of the BB with the isocenter or determine the coincidence of the BB from central axis automatically. To test the percision of this tool a set of images with known shifts were taken at gantry angles (0, 90, 180 and 270 degrees) using a 17.5 mm Conical Collimator delimited field with 100 MU per dosimeteric image at a dose rate of 300 Gy/MU and 6X photon energy. The images were programmatically analyzed and the shifts were calculated. The known shift and the calculated shift was then compared.
Results: Image analysis indicates that the software program calculates the shifts with an error less than 0.5 mm. Further tests indicate that the isocenter size can be determined using this tool within close relation to to other open-source Winston-Lutz test analysis application.
Conclusion: This work indicates that a custom-made software application can be beneficial when performing QA to check for the mechanical stability of the rotation axes of the linac. The analysis time recorded for this test was greatly reduced from a manually analysis performed of the same image.
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