Dosimetric characterization of a large area pixel-segmented ionization chamber

被引:72
作者
Amerio, S
Boriano, A
Bourhaleb, F
Cirio, R
Donetti, M
Fidanzio, A
Garelli, E
Giordanengo, S
Madon, E
Marchetto, F
Nastasi, U
Peroni, C
Piermattei, A
Freire, CJS
Sardo, A
Trevisiol, E
机构
[1] Dipartimento Fis Sperimentale, I-10125 Turin, Italy
[2] Ist Nazl Fis Nucl, I-10125 Turin, Italy
[3] AOS Giovanni Battista, Presidio S Giovanni AS, I-10100 Turin, Italy
[4] Fdn TERA, I-28100 Novara, Italy
[5] Univ Cattolica SC Roma, Ist Fis, I-00168 Rome, Italy
[6] ASP, I-10125 Turin, Italy
[7] AO OIRM S Anna, I-10126 Turin, Italy
关键词
dosimetric characterization; 2D ionization chamber array; radiation therapy quality assurance;
D O I
10.1118/1.1639992
中图分类号
R8 [特种医学]; R445 [影像诊断学];
学科分类号
1002 ; 100207 ; 1009 ;
摘要
A pixel-segmented ionization chamber has been designed and built by Torino University and INFN. The detector features a 24 X 24 cm 2 active area divided in 1024 independent cylindrical ionization chambers and can be read out in 500 mus without introducing dead time; the digital charge quantum can be adjusted between 100 fC and 800 W. The sensitive volume of each single ionization chamber is 0.07 cm(3). The purpose of the detector is to ease the two-dimensional (2D) verifications of fields with complex shapes and large gradients. The detector was characterized in a PMMA phantom using Co-60 and 6 MV x-ray photon beams. It has shown good signal linearity with respect to dose and dose rate to water. The average sensitivity of a single ionization chamber was 2.1 nC/Gy, constant within 0.5% over one month of daily measurements. Charge collection efficiency was 0.985 at the operating polarization voltage of 400 V and 3.5 Gy/min dose rate. Tissue maximum ratio and output factor have been compared with a Farmer ionization chamber and were found in good agreement. The dose profiles have been compared with the ones obtained with an ionization chamber in water phantom for the field sizes supplied by a 3D-Line dynamic multileaf collimator. These results show that this detector can be used for 2D dosimetry of x-ray photon beams, supplying a good spatial resolution and sensibly reducing the time spent in dosimetric verification of complex radiation fields. (C) 2004 American Association of Physicists in Medicine.
引用
收藏
页码:414 / 420
页数:7
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