Program Information
Using ArcCHECK as a 3D QA Tool for Brachytherapy Applicators: A Feasibility Study
G Cohen1*, A Guemnie Tafo2 , J Kapatoes3 , S Koren4 , (1) Memorial Sloan-Kettering Cancer Center, New York, NY, (2) Institute Gustave Roussy, Paris, France,(3) Sun Nuclear Corporation, Melbourne, FL, (4) Ziv Medical Center, Safed, Israel
Presentations
SU-E-205-8 (Sunday, July 30, 2017) 1:00 PM - 1:55 PM Room: 205
Purpose: QA of brachytherapy applicators is usually limited to visual and radiographic inspections, and dose distributions around applicators of complex geometry are not easily measured. This is of particular concern for applicators devised or 3D-printed in house that lack vendor validation. We propose using ArcCHECK to assist in routine end to end validation of brachytherapy applicators.
Methods: The ArcCHECK cavity was filled with sponge, in which titanium HDR needles were inserted. One needle was placed on top of the device for calibration. A CT scan of the device and needles was acquired (1mm slice thickness, 30cm FOV) and reconstructed (BrachyVision, Varian Medical Systems). For calibration, a single channel with 5cm length treatment exposed the diodes participating in the calibration procedure to a pre-calculated dose. Plans simulated vaginal cylinders, Tandem & Ring, and Tandem & Split-Ring applicators. Acuros inhomogeneity correction was applied to all calculations to account for air within and around the device. Plans were exported to the device and afterloader, and executed. Measurements were compared with expected dose profiles and scored.
Results: Two dimensional gamma and distance-to-agreement analyses using 3% local dose difference 3mm distance-to-agreement resulted in a passing rate of 91% for single-channel and 85% for multi-channel plans; 2%-2mm analysis yielded 88% and 78% passing rates for single and multi-channel plans, respectively.
Conclusion: The results of this initial investigation are encouraging. Careful device calibration for Ir-192 is required. Factors contributing to systematic error include a lack of Ir-192-specific correction factors for ArcCHECK diodes, limitations in Acuros heterogeneity corrections in modeling metallic components of the device and applicators, and the transit dose contribution that increases for the multi catheter treatments conducted here.We have demonstrated the feasibility of applicator and patient specific QA for HDR Brachytherapy procedures using the ArcCHECK system.
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