Dosimetric characterization of a large area pixel-segmented ionization chamber
Dosimetric characterization of a large area pixel-segmented ionization chamber
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DOI：
10.1118/1.1639992
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发表时间：
2004-02-01
期刊：
影响因子：
3.8
通讯作者：
Trevisiol, E
中科院分区：
文献类型：
--
作者：
Amerio, S;Boriano, A;Trevisiol, E
都灵大学和INFN设计并建造了一个像素分段电离室。探测器的有效面积为24x24cm2，分为1024个独立的圆柱形电离室，可在500微秒内读出，不引入死区时间；数字电荷量可在100fC至800W之间调节；每个电离室的灵敏度体积为0.07 cm(3)。探测器的目的是简化具有复杂形状和大梯度的场的二维(2D)验证。该探测器在PMMA模体中用Co-60和6 mV X射线光子束进行了表征。它对水的剂量和剂量率表现出良好的信号线性。单室电离室的平均灵敏度为2.1nC/Gy1个月的每日测量恒定在0.5%以内。在极化电压为400V，剂量率为3.5Gy/min时，电荷收集效率为0.985。将组织最大比和输出因子与Farmer电离室进行了比较，发现两者吻合较好。在3D-Line动态多叶准直器提供的射野大小下，将剂量分布与水模电离室获得的剂量分布进行了比较。这些结果表明，该探测器可以用于X射线光子束的二维剂量学测量，提供了良好的空间分辨率，并有效地减少了复杂辐射场的剂量学验证时间。(C)2004年美国医学物理学家协会。
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.