I'mRT MatriXX Array Characterization And Spatial Modification Simulations In Intensity Modulated Radiation Theraphy (IMRT) At 6 MV Photon Beam In Nasopharynx Cancer
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Date
2011-12
Authors
alAshrah, Saleh Abdullah
Journal Title
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Publisher
Universiti Sains Malaysia
Abstract
Two types of 2D pixel ionization chambers: I’mRT MatriXX from Scanditronix- Wellhöfer in Mount Mariam Hospital and Seven29TM from PTW‐Freiburg in King Faisal special Hospital and Research Center (KFSH&RC) in Riyadh were studied with the objective to implement for quality assurance in IMRT treatment plan verification. The effective point measurement of the I’mRT MatriXX and Seven29TM were verified and it agreed with the manual specifications. The reproducibility of the I’mRT MatriXX detector was tested for the short-, medium- and long-term. The reproducibility was within 1.9%. Dose linearity and energy independence were also analyzed. The results showed that the dose was linear and the response of the 2D arrays was independent of energy. The effect of different field sizes on the response of the 2D arrays was performed and compared with the ionization chambers. The dose rate was also linear with the response of the 2D arrays. The profile measurements for field sizes 2×2, 5×5, 8×8 and 10×10 cm2 were performed and compared with those obtained using the ionization chamber. The results showed that the response of the I’mRT MatriXX should be corrected in the penumbra region especially for small field sizes such as 2×2 and 3×3 cm2. However, the beam profiles measured by Seven29TM better matched profiles obtained from PTW 30006 compared to those measured using I’mRT MatriXX. One main reason is that the distance between two ionization chambers of Seven29TM matches the width of MLCs at the isocenter.
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Keywords
I'mRT MatriXX array characterization and spatial modification simulations , intensity modulated radiation theraphy