Dose rate and SDD dependence of commercially available diode detectors
Dose rate and SDD dependence of commercially available diode detectors
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DOI：
10.1118/1.1650563
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发表时间：
2004-04-01
期刊：
影响因子：
3.8
通讯作者：
Zhu, TC
中科院分区：
文献类型：
--
作者：
Saini, AS;Zhu, TC
市售的二极管探测器的剂量率依赖性进行了测量下的高瞬时剂量率（脉冲）和低剂量率（连续，Co-60）辐射。剂量率依赖性是在丙烯酸微型体模中测量的，深度为5 cm，准直器设置为10 × 10 cm（2），通过在至少80 cm和200 cm之间改变源-探测器距离（SDD）。标准化二极管阅读与标准化离子室阅读的比率（均在SDD = 100 cm处）用于确定在不同SDD处脉冲和连续辐射的二极管灵敏度比率。二极管灵敏度比的倒数被定义为SDD校正因子（SDD CF）。二极管的灵敏度比随瞬时剂量率的增大而增大（或随SDD的减小而增大）。二极管灵敏度的比率，归一化为4000 cGy/s，在0.988（1490 cGy/s）-1.023（38900 cGy/s），对于未辐照的n型Isorad Gold，0.981（1460 cGy/s）- 1.026（39 060 cGy/s）对于未辐照的QED红（n型），0.972（1490 cGy/s）-1.068（38 900 cGy/s），对于预辐照的Isorad Red（n型），0.985（1490 cGy/s）-1.012（38990 cGy/s），对于n型Pt掺杂的Isorad-3金，0.995（1450 cGy/s）-1.020（21870 cGy/s），对于n型Veridose绿色，0.978（1450 cGy/s）-1.066（21870 cGy/s），对于预辐照Isorad-p Red，0.994（1540 cGy/s）- 1.028（17 870 cGy/s），P型预辐照QED为0.998（1450 cGy/s）-1.003（21870 cGy/s），而Scanditronix EDP 10（3G）二极管为0.998（1490 cGy/s）-1.015（38880 cGy/s）。p型二极管的剂量率依赖性并不总是比n型二极管小。预辐照并不总是减少二极管的剂量率依赖性。比较了在全散射体模和微型体模表面测得的SDD依赖性。使用辐射脉冲高度的直接调整，我们得出结论，二极管灵敏度的SDD依赖性可以解释的瞬时剂量率依赖性，如果提供足够的建设，以消除电子污染。提出了一个与能量无关的经验公式来拟合二极管灵敏度与剂量率的关系。(C)2004年美国医学物理学家协会。
The dose-rate dependence of commercially available diode detectors was measured under both high instantaneous dose-rate (pulsed) and low dose rate (continuous, Co-60) radiation. The dose-rate dependence was measured in an acrylic miniphantom at a 5-cm depth in a 10 X 10 cm(2) collimator setting, by varying source-to-detector distance (SDD) between at least 80 and 200 cm. The ratio of a normalized diode reading to a normalized ion chamber reading (both at SDD = 100 cm) was used to determine diode sensitivity ratio for pulsed and continuous radiation at different SDD. The inverse of the diode sensitivity ratio is defined as the SDD correction factor (SDD CF). The diode sensitivity ratio increased with increasing instantaneous dose rate (or decreasing SDD). The ratio of diode sensitivity, normalized to 4000 cGy/s, varied between 0.988 (1490 cGy/s)-1.023 (38900 cGy/s) for unirradiated n-type Isorad Gold, 0.981 (1460 cGy/s)- 1.026 (39 060 cGy/s) for unirradiated QED Red (n type), 0.972 (1490 cGy/s)-1.068 (38 900 cGy/s) for preirradiated Isorad Red (n type), 0.985 (1490 cGy/s)-1.012 (38990 cGy/s) for n-type Pt-doped Isorad-3 Gold, 0.995 (1450 cGy/s)-1.020 (21870 cGy/s) for n-type Veridose Green, 0.978 (1450 cGy/s)-1.066 (21870 cGy/s) for preirradiated Isorad-p Red, 0.994 (1540 cGy/s)- 1.028 (17 870 cGy/s) for p-type preirradiated QED, 0.998 (1450 cGy/s)-1.003 (21 870 cGy/s) for the p-type preirradiated Scanditronix EDP20(3G), and 0.998 (1490 cGy/s)-1.015 (38 880 cGy/s) for Scanditronix EDP10(3G) diodes. The p-type diodes do not always show less dose-rate dependence than the n-type diodes. Preirradiation does not always reduce diode dose-rate dependence. A comparison between the SDD dependence measured at the surface of a full scatter phantom and that in a miniphantom was made. Using a direct adjustment of radiation pulse height, we concluded that the SDD dependence of diode sensitivity can be explained by the instantaneous dose-rate dependence if sufficient buildup is provided to eliminate electron contamination. An energy independent empirical formula was proposed to fit the dose-rate dependence of diode sensitivity. (C) 2004 American Association of Physicists in Medicine.