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Commissioning of Varian Horizontal HDR Leipzig- Style Surface Applicator

A Amoush1, N Vassell2, N Kalach3*, (1) Mount Sinai Health System, New York, NY, (2) Mount Sinai Health System, New York, New York, (3) Norwalk Hospital Radiation Oncology, Norwalk, CT

Presentations

PO-GePV-T-30 (Sunday, 7/10/2022)   [Eastern Time (GMT-4)]

ePoster Forums

Purpose: The purpose of this study is to commission and clinically implement the Varian Leipzig surface applicator with the source horizontally positioned for HDR Brachytherapy

Methods: The applicators set includes 1 Leipzig-style cone with holder and guide and 4 round surface cone insets with 30mm, 35mm, 40mm and 45mm in diameter. Initial inspection of the set includes visual inspection for any visible defects, test of holder and proper fixation of inserts, labeling of the inserts, and measurements of the insert diameter. Following that, air kerma strength, percentage depth doses (PDDs), dose profiles, and absolute point dose measurements were performed using 0.074cc NIST calibrated Exradin A20 parallel-plate Ion Chamber and GafChromic films. All measurements were compared with the Monte Carlo (MC) data by the vendor. Safety tests were also performed to prevent any mistreatment.

Results: All applicators were found to be functional with physical dimensions within 1 mm of specifications. All profiles agree with vendor provided MC data to within 1mm for full width at 90% dose level. For PDDs, our results agreed within 5% of vendor provided MC data. Dose rate at the surface using the A20 chamber was 4.6%, 6.5%, 9.1%, and 6.4% for 30mm, 35mm, 40mm, and 4.5 mm applicator, respectively. Measured PDDs up to 20 mm depth normalized to 3mm depth showed good agreement with the vendor MC data with deviation less than 5% for most depths but it exceeded 5% (maximum of 6.88%) for depths larger than 7mm for the 35mm and 40mm applicators. The full width of the 90% isodose level profiles at depth of 3mm agreed within 1mm with the vender data. Absolute point dose difference between measured and vendor data were 1.64% and 4.8% for the 30mm and 40mm, respectively

Conclusion: Leipzig surface applicator was successfully commissioned and clinically used for skin treatments.

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