Dose rate determination for 125I seeds.
Dose rate determination for 125I seeds.
复制标题
125I 种子的剂量率测定。
DOI：
10.1118/1.596586
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发表时间：
1990
期刊：
影响因子：
3.8
通讯作者：
Sanna,R
中科院分区：
文献类型：
--
作者：
Chiu-Tsao,ST;Anderson,LL;O'Brien,K;Sanna,R
近距离放射治疗中使用的两种125 I粒子的水中剂量率已经确定。当发现用硅二极管测量的水/空气比低于预期时，这种测定的必要性变得明显。使用氟化锂热释光剂量计（dos）在固体水模型中进行了广泛的测量，距离种子中心0.1至10 cm，在通过种子轴的平面内以10°、15°或30°的角增量进行。通过在空气中用相同类型和强度的125 I种子进行辐照，完成了放射性同位素的剂量校准，这些种子可追溯到美国国家标准与技术研究所（NIST）的校准。通过在烘箱型X射线机中同时辐照对照剂量计以及所有剂量计与125 I辐照间歇进行辐照，监测放射性同位素的相对校准。获得的剂量率常数值，即，对于6711和6702粒子，横轴上1 cm处每单位空气比释动能强度的剂量率分别为0.853和0.932 cGy h−1U−1（1.08和1.18 cGy h− 1 mCi −1）。测量数据补充了使用莫尔斯代码生成的蒙特卡罗计算的相对剂量率数据。这些计算使用了100个能量群，从10到35.4千电子伏，涉及的能量收集箱的边缘从0.025到1.2厘米。在1 cm处归一化，横轴计算数据与距离为8 cm处的测量数据（我们的或引用的文献）无显著差异<2.5 or >。在沿横轴沿着的不同距离处进行归一化，我们的离轴计算和测量分布在所有角度处都非常一致，但在小距离（≤1 cm）处与文献测量分布不同，并且对于小角度，在较大距离（≥5 cm）处的差异越来越大。
Dose rates in water have been determined for the two types of125I seed currently used in brachytherapy. The need for such determinations became evident when water/air ratios measured with a silicon diode were found to be lower than expected. Extensive measurements using lithium fluoride thermoluminescent dosimeters (TLD's) have been performed in a solid water phantom, at distances from 0.1 to 10 cm from the seed center and at angular increments of 10°, 15°, or 30° within a plane through the seed axis. Dose calibration of the TLD's was accomplished by irradiation in air with125I seeds of the same type and of strengths traceable to a calibration at the National Institute of Standards and Technology (NIST). Relative calibration of TLD's was monitored by irradiation, in an oven‐type x‐ray machine, of control dosimeters simultaneously and all dosimeters intercurrently with the125I irradiations. Values obtained for the dose rate constant, i.e., dose rate per unit air‐kerma strength at 1 cm on the transverse axis, were 0.853 and 0.932 cGy h−1U−1(1.08 and 1.18 cGy h−1mCi−1) for the 6711 and 6702 seeds, respectively. Measured data were supplemented with Monte Carlo‐calculated relative dose rate data generated using the MORSE code. These calculations used 100 energy groups from 10 to 35.4 keV and involved energy collection bins ranging from 0.025 to 1.2 cm on an edge. Normalized at 1 cm, transverse axis calculated data are not significantly different from measured data (ours or cited literature) at distances either <2.5 or >8 cm. Normalized at different distances along the transverse axis, our off‐axis calculated and measured distributions agree closely at all angles but differ from literature measured distributions at small (≤1 cm) distances and, for small angles, increasingly at larger distances (≥5 cm).