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KMID : 0384620060170030131
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Korean Journal of Medical Physics
2006 Volume.17 No. 3 p.131 ~ p.135
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Dosimetric Characterization of an Ion Chamber Matrix for Intensity Modulated Radiation Therapy Quality Assurance
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Lee Jeong-Woo
Hong Se-Mie
Kim Yeon-Re
Choi Kyung-Seek
Chung Jin-Beom
Lee Do-Hyun
Suh Tae-Suk
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Abstract
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A commercial ion chamber matrix was examined the characteristics and its performance for radiotherapy qualify assurance. The device was the I’’mRT 2D-MatriXX (Scanditronix-Wellhofer, Schwarzenbruck, Germany). The 2D-MatriXX device consists of a 1020 vented ion chamber array, arranged in matrix. Each ion chamber has a volume of spacing of 0.762 cm and minimum sampling time of 20 ms. For the investigation of the characteristics, dose linearity, output factor, short-term reproducibility and dose rate dependency were tested. In the testing of dose linearity. It has shown a good signal linearity within 1% in the range of cGy. Dose rate dependency was found to be lower than 0.4% (Range: 100-600 Mu/min) relative to a dose rate of 300 Mu/min as a reference. Output factors matched very well within 0.5% compared with commissioned beam data using a ionization chamber (CC01, Scanditronix-Wellhofer, Schwarzenbruck, Germany) in the range of field sizes. Short-term reproducibility (6 times with a interval of 15 minute) was also shown a good agreement within 0.5%, when the temperature and the pressure were corrected by each time of measurement. in addition, we compared enhanced dynamic wedge (EDW, Varian, Palo Alto, USA) profiles from calculated values in the radiation planning system with those from measurements of the MatriXX. Furthermore, anon-uniform IMRT dose fluence was tested. All the comparison studies have shown good agreements. In this study, the MatriXX was evaluated as a reliable dosimeter, and it could be used as a simplistic and convenient tool for radiotherapy qualify assurance
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KEYWORD
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2D-MatriXX, IMRT
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