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Experimental Validation of the Valencia-Type Applicators Developed for the BEBIG HDR Afterloader Saginova

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J Perez-Calatayud

V Pastor-Sanchis1 , A Bartres1 , M Erzilbengoa1 , A Guisasola1 , P Mejide2 , M Andrassy2 , D Granero3 , F Ballester4 , J Perez-Calatayud5*, (1) Onkologikoa Fundazioa, Donostia-san Sebastian, Guipuzcoa, (2) E&Z Bebig, Berlin, Berlin, (6) E&Z Bebig, Berlin, Berlin, (3) Eresa. Hospital General Universitario., Valencia, Valencia, (4) University of Valencia, Burjassot, ,(5) Hospital La Fe, Valencia,


TU-RPM-GePD-TT-2 (Tuesday, August 1, 2017) 3:45 PM - 4:15 PM Room: Therapy ePoster Theater

Purpose: The Valencia Applicators are extensively used in skin brachytherapy. They are made of tungsten in a conical design with just one dwell position at the cone vertex. An internal flattering filter creates a uniform dose distribution in the treatment area with very small penumbra (Granero 2008). E&Z Bebig has developed two Valencia applicators, BVH-20 and BVH-30 with nominal diameter 2 and 3 cm, for its afterloader Saginova®. A Monte Carlo (MC) study [Anagnostopoulos 2017] was performed to design the filter and derived their dosimetric characteristics. The aim of this study is the experimental validation of the MC data.

Methods: Flatness, symmetry, absolute output and PDD were measured for 3 sets of the Bebig Valencia applicators in a solid state phantom. Flatness and symmetry were measured with EBT3 film at the prescription depth of 3 mm and analysed independently by two institutions. Absolute output was determined using the Pin-Point ionization chamber (T31016, PTW, Germany) calibrated in Co-60. PDD-distributions were measured with a parallel plate ionization chamber (Advanced-Markus chamber, T34045, PTW). Film dosimetry was used also for PDD measurements. The phantom was built with standard RW3 slabs and adapter plates for the ionization chambers (T29672, PTW).

Results: The Output Factor at 3 mm depth was 0.180 cGy/(h U) and 0.144 cGy/(h U) for the BVH-20 and BVH-30, respectively. Both results (uncertainty 2.6%, k=1) agree with the Monte Carlo data within their uncertainties. Parallel-plate ionization chamber -, EBT3- and MC-PDD data agree within 3%. The dosimetric data were reproducible for the 3 investigated applicator sets.

Conclusion: Dosimetric data have been measured for the E&Z Bebig Valencia Applicators BVH-20 and BVH-30 resulting in excellent agreement with the MC calculations. They represent the reference data sets for clinical use, and the applied methodology can serve for commissioning by future users.

Funding Support, Disclosures, and Conflict of Interest: The authors thank E&Z BEBIG for their support of this study

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