Comparison of p-type commercial electron diodes for in vivo dosimetry
Comparison of p-type commercial electron diodes for in vivo dosimetry
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DOI：
10.1118/1.1630492
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发表时间：
2004-01-01
期刊：
影响因子：
3.8
通讯作者：
Marinello, G
中科院分区：
文献类型：
--
作者：
Marre, D;Marinello, G
本文比较了三种专门设计用于体内剂量测定的商用p型电子二极管（scanitronix EDD2、Sun Nuclear QED 111200-0和PTW T60010E二极管与Therados DPD510剂量计耦合）在能量为4.5 - 21 MeV的电子场中以及与放射治疗相似的条件下的特性。除了二极管外，实验中还使用了NACP平面平行电离室和膜剂量计。研究了光束方向对二极管响应（定向效应）的影响。在电子束能量最低的情况下，它是最大的。在12 MeV和+/-30度入射下，发现scanitronix和Sun Nuclear二极管的变化小于1%，而PTW二极管的变化小于3%。在0.18-0.43 mGy/脉冲范围内，三个二极管的灵敏度变化小于1%。研究了温度依赖性。在22.2 ~ 40°c范围内，三种二极管的响应呈线性，灵敏度随温度的变化分别为（0.25+/-0.01）%/°c、（0.28+/-0.01）%/°c、（0.02+/-0.01）%/°c和（0.02+/-0.01）%/°c。最后，对放置在均匀体表面的二极管的存在所引起的辐照场扰动进行了研究，并发现对于所有三种二极管类型，在表面和最大剂量深度（几十个百分点）都是显著的。在二极管正下方（靠近表面）有剂量增加，在最大深度处有剂量阴影。研究表明，如果在使用前仔细确定电子二极管的特性，并在解释结果时考虑到这些特性，则电子二极管可以用于体内剂量测定。(C) 2004年美国医学物理学家协会。
This paper compares the characteristics of three types of commercial p-type electron diodes specially designed for in vivo dosimetry (Scanditronix EDD2, Sun Nuclear QED 111200-0 and PTW T60010E diodes coupled with a Therados DPD510 dosimeter) in electron fields with energies from 4.5 to 21 MeV, and in conditions similar to those encountered in radiotherapy. In addition to the diodes, a NACP plane parallel ionization chamber and film dosimeters have been used in the experiments. The influence of beam direction on the diode responses (directional effect) was investigated. It was found to be the greatest for the lowest electron beam energy. At 12 MeV and an incidence of +/-30degrees, the variation was found to be less than 1% for the Scanditronix and Sun Nuclear diodes and less than 3% for the PTW one. The three diodes exhibited a variation in sensitivity with dose-per-pulse of less than 1% over the range 0.18-0.43 mGy/pulse. The temperature dependence was also studied. The response was linear for the three diodes between 22.2 and 40 degreesC and the sensitivity variations with temperature were (0.25+/-0.01)%/degreesC, (0.28+/-0.01)%/degreesC, and (0.02+/-0.01)%/degreesC for Scanditronix, Sun Nuclear, and PTW diodes, respectively. Finally the perturbation to the irradiation field induced by the presence of diodes placed at the surface of a homogeneous phantom was investigated and found to be significant, both at the surface and at the depth of maximum dose (several tens of percent) for all three diode types. There is an increase of dose right underneath the diode (close to the surface) and a dose shadow at the depth of maximum. The study shows that electron diodes can be used for in vivo dosimetry provided their characteristics are carefully established before use and taken into consideration at the time of interpretation of the results. (C) 2004 American Association of Physicists in Medicine.