60Co陀螺刀的剂量特性验收测试

目的 介绍和评估 ⁶⁰Co陀螺刀的剂量学特性。方法 分别用0.015、0.600 cm³电离室,EDR2胶片和半导体探测器测量4个直径分别为5、12、30、50 mm准直器等中心剂量率。用0.015 cm³电离室检验机器的剂量—时间线性关系和机器出束稳定性。用0.015 cm³电离室探头与半导体探头测量治疗计划系统(TPS)计算和测量的相对误差,用胶片测量TPS计算等剂量线在x、y轴方向宽度误差。结果 0.015、0.600 cm³电离室,EDR2胶片和半导体探测器对50 mm准直器测量无差别,对5 mm准直器差别最大。半导体探测器测量的TPS与实测剂量误差最大为4.8%,大部分测量结果都<3.0%。50%等剂量线x轴方向差异最大为4.9 mm,其他都<2.0 mm。结论 ⁶⁰Co陀螺刀具有良好的剂量学特性,适合立体定向放疗。

Commissioning of GyroKnife digital cobalt-60 system for stereotactic radiotherapy and radiosurgery in dosimetric aspects

Objective To introduce and evaluate the dosimetric characteristics of a GyroKnife cobalt-60 system for radiosurgery. Methods 0.015 cm³ and 0.600 cm³ ionization chamber, EDR2 film and semiconductor dosimeter were used to measure the dose rate of center point for the four collimators. The diameter of the four collimators were 5 mm,12 mm,30 mm and 50 mm,respectively. 0.015 cm³ ionization chamber was used to test the dose-time linear relationship and dose stability. 0.015 cm³ ionization chamber and semiconductor was used to measure the dose error of phantom between treatment planning system (TPS) calculation and measurement. The film was used to measure the error of TPS calculation isodose lines width. Results The results from the four measurement methods have no significant difference for the collimator 50 mm. But for collimator 5 mm great discrepancy appeared. The error between calculation by TPS and the measurement by semiconductor was biggest and the value was 4.8%. Most of the error was within 3.0%.The error of the 50% isodose line along x-axis was biggest and the value was 4.9 mm,others are all within 2.0 mm. Conclusion The dosimetric character of this system is suitable for stereotactic radiotherapy.