Document Type : Conference Proceedings
Secondary Standard Dosimetry Laboratory (SSDL), Pars isotope Co., Karaj, Iran.
Associate Professor, Radiology Technology Department, Allied Medical Faculty, Shahid Beheshti University of Medical Science,Tehran, Iran
Tajrish Shohada Hospital, Tehran, Iran.
Introduction: Quality assurance is essential for obtaining the best achievable tumor control, avoiding unnecessary side effects, accuracy and safety during performing High Dose Rate (HDR) Brachytherapy (BT). Quality assurance is extremely important because HDR BT procedures are performed quickly, with high doses given in a short time period, with little opportunity for correction. The quality assurance procedure can be divided into the four categories: Treatment unit, Treatment Planning System (TPS), Imaging and Patient treatment procedure. These categories include different tests which should to be done periodically in order to verify the accurate treatment. In this study a number of important quality assurance tests were performed.
Materials and Methods: Physical and Safety parameters of the Sagi Nova (Eckert & Ziegler Bebig GmbH) machine with Co-60 source was investigated. Determination of source position accuracy was done in two methods 1) video-ruler source position and 2) Gafchromic film with posi check phantom (PTW, Germany). Reference Air Kerma Strength (RAKS) of the source was measured according to IAEA TECDOC-1274 using a well-type ionization chamber (PTW, Germany) with suitable holder for insertion of the afterloader's catheter. Another physical parameter like Length of treatment tubes, Transit time, Timer consistency and Timer linearity were measured. Safety parameters like Communication equipment, Applicator attachment, Catheter attachment lock, Door interlock, warning lights, Room monitor, Hand held monitor, Treatment interrupt, and Emergency stop were evaluated.
All items related to safety parameters investigated and defects have been resolved. Source positioning accuracy in both video-ruler and Gafchromic measurement showed a difference of less than one millimeter. RAKR measured by the well-type ionization chamber in comparison with the input value in the TPS showed a 0.5% difference which is acceptable.
Conclusion: Quality assurance of Sagi Nova HDR BT machine was performed. Physical and Safety parameters were investigated. The measurements showed acceptable results. Because of the high importance of HDR BT treatment, it is recommended each center perform quality assurance tests according to the existing protocols in the regular time interval.