Program Information
Surface Electronic Brachytherapy Dosimetry: Comparison and Uncertainty Evaluation of Different Calibration Protocols and Ionization Chambers
C Candela-Juan1*, T Garcia-Martinez2 , Y Niatsetski3 , J Schuurman3 , G Nauta3 , J Vijande4 , Z Ouhib5 , F Ballester4 , J Perez-Calatayud1,6 , (1) La Fe University and Polytechnic Hospital, Valencia, Spain, (2) Hospital La Ribera, Alzira, Spain, (3) Elekta Brachytherapy, Veenendaal, The Netherlands, (4) University of Valencia, Burjassot, Spain,(5) Lynn Regional Cancer Center, Delray Beach, FL,(6) Hospital Clinica Benidorm, Benidorm, Spain
Presentations
SU-E-T-720 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: The Esteya electronic brachytherapy system (Elekta Brachytherapy, The Netherlands) has been recently developed for HDR brachytherapy treatment of skin lesions, using a 69.5 kVp x-ray source and a set of applicators that generate beams of 1 to 3 cm diameter. The purpose of this study was to evaluate the surface dose rate of the Esteya (and its estimated uncertainty) by using different detectors and calibration protocols.
Methods: The surface dose rates for the different applicators were measured with the plane parallel ionization chamber T34013 (PTW-Freiburg, Germany) and the parallel plate ionization chamber Exradin A20 (Standard Imaging Inc., USA). The first one was calibrated in both air and water, whereas the second one was provided with calibration in air. Two different chambers of each type were used to evaluate detector reproducibility. Measurements in air were performed according to dosimetric protocol established by the TG-61 of the AAPM, whereas measurements in water were performed in a CIRS Plastic Water LR phantom, using the methodology proposed by the TRS-398 of IAEA. The correction factors of each protocol and ionization chamber were carefully evaluated.
Results: Differences between surface dose rates measured in-air and in-water using the T34013 chamber range from 1.6% to 3.3%. Differences are below 3.7% when measurements with the A20 and the T34013 chambers calibrated in air are compared. However, absorbed dose rates measured with the A20 chamber in air and the T34013 chamber in water differ up to 6%. Estimated uncertainties are of the order of 2.5% (with coverage factor k=1). The output factors measured with the PTW chambers differ by less than 1.1% when compared to the values measured with the A20 chamber.
Conclusion: The two ionization chambers and the two dosimetric protocols provide consistent results considering the combined uncertainties. Both chambers have negligible stem effect.
Funding Support, Disclosures, and Conflict of Interest: This study was supported in part by Generalitat Valenciana under Project PROMETEOII/2013/010 and by Spanish Government under Project No. FIS2013-42156. Funding was also received by Elekta and PTW.
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