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Program Information

Quality Assurance for CO60 HDR Brachytherapy

G Gonzalez Sprinberg

G Gonzalez Sprinberg1*, H Ortega1 , G Piriz2 , C Vega 1, (1) Universidad de la Republica, Montevideo,Uruguay, (2) Centro Hospitalario Pereyra Rossell, Montevideo, Uruguay


SU-I-GPD-T-14 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Quality assurance in source position using an insert for well-type chambers for high dose rate remote afterloaders with Co-60 sources.

Methods: A quality assurance Cerrobend insert was built for HDR brachytherapy equipped with Co-60 sources. It consisted in a cylinder with a transverse spacer of acrylic at a precisely known distance from the source. The distance of the source to this acrylic window determines the response of the detector to the signal. We used a Co-60 HDR afterload system (E&Z BEBIV 60 Co HDR Co0-A86, Berlin, Germany) and a well-type chamber (PTW 33004, Freiburg, Germany). Different sizes for the acrylic window where tested in order to optimize the signal. The dwell position step was 5 mm and a vernier caliper fixed to the holder allowed to select different steps. Background current with no window was subtracted in order to determine the source position accuracy.

Results: The current shape curve and maximum was well reproduced for windows up to 5 mm size when the measured background with no window was subtracted. Two curves constructed in this way, built with 14 steps at 5 mm each and another one with an offset of 2.5 mm allows to determine the source position better than ±2 mm accuracy.

Conclusion: This methodology may provide a easy way to periodically check source position accuracy for HDR Co-60 sources in brachytherapy up to ±2 mm accuracy, in a similar way as the Standard Imaging HDR 1000 QA Tool allows to do for Ir-192 sources. Other materials for the device, such a tungsten, are being considered in order to improve resolution and accuracy of this method.

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