Commissioning Bebig Valencia-Type Applicators for a Bravos Afterloader
Abstract
Purpose
A Valencia-type applicator was recently created by Bebig for use with Varian GammaMedPlus and Varian Bravos afterloaders using an Ir-192 source. To our knowledge, we are the first site to use this applicator with a Bravos afterloader.
Methods
20mm and 30mm Valencia-type applicators were obtained for use with a Bravos afterloader. The source to indexer distance (SID) was measured using a HDR 1000 Plus well chamber and Leipzig Applicator Source Holder (well chamber setup). Output was checked via the correspondence factor and the output factor. The correspondence factor was measured with the well chamber setup. The output factor measurement used an Exradin A16 chamber at a depth of 1cm. Dosimetry profiles were measured at the reference depth of 3mm using EBT3 film. Percent depth dose (PDD) values were measured from 1mm to 10mm at 1mm increments with an Exradin A10 chamber. All measurements were compared to the Bebig Instructions for Use (IFU) document with the tolerances suggested by Granero et al. An additional output check was done with thermoluminescent dosimeters (TLD).
Results
The SID was found to be 112mm for the 20mm and 30mm applicators. Correspondence factors for the 20mm and 30mm applicators were measured as 0.169 and 0.189 (2.8% and -0.30% error), respectively, and are within a 5% tolerance of IFU values. The output factor was calculated to be 0.2234 cGyh-1U-1 and 0.1718 cGyh-1U-1, respectively, and are within uncertainty. Flatness was measured as 2.70% and 2.60% and symmetry as 0.19% and 0.14%, respectively. Flatness and symmetry measurements were within the suggested 5% tolerance. All PDD values were found to be within a 1% and 2% delta of the values suggested in the IFU, respectively. The TLD measurements had a 3.61% and -0.18% error, respectively.
Conclusion
The Valencia-type applicators were successfully commissioned for use with a Bravos afterloader.