125I粒子持续低剂量率照射胰腺癌细胞株PANC-1相对生物效应的研究

目的 探讨国产6711型¹²⁵I粒子的相对生物效应,并对其照射杀伤PANC-1细胞的效果进行了初步探讨。方法 PANC-1细胞处于指数生长期时,行¹²⁵I粒子离体照射;在初始剂量率为2.59 cGy/h时,分别给予1、2、4、6、8和10 Gy照射。⁶⁰Co照射作为对照组,吸收剂量率为2.21 Gy/min,给予相同剂量照射。用锥虫蓝染色法检测细胞死亡比率,并比较在4 Gy照射后培养12、24、48和72 h细胞死亡率随时间变化。采用克隆形成实验,计算细胞克隆形成率,绘制生存曲线,得出生物学参数,并测定¹²⁵I粒子与⁶⁰Co的相对生物效应。结果 在相同剂量照射下,¹²⁵I持续低剂量率照射与⁶⁰Co照射相比,当≥4 Gy时,细胞死亡率明显增高。在4 Gy照射后,随着时间延长细胞死亡率增高,两者相比有明显差异。从生存曲线分析,¹²⁵I粒子持续低剂量率照射细胞存活分数比60Co低,¹²⁵I粒子相对于⁶⁰Co的生物效应为1.45。结论 ¹²⁵I粒子持续低剂量率照射与⁶⁰Co高剂量率照射相比,细胞杀伤效应更强;测定的相对生物效应与其他研究者测量的结果相似;将为临床¹²⁵I粒子治疗肿瘤提供一定的参考价值。

Relative biological effectiveness of 125I seeds for low-dose-rate irradiation of PANC-1

Objective To investigate the relative biological effectiveness(RBE) of National Model 6711 ¹²⁵I seeds and the response patterns of PANC-1 exposed to ¹²⁵I seeds irradiation. Methods PANC-1 cells in exponential growth were irradiated at initial dose rate of 2.59 cGy/h in vitro and exposed to 1, 2, 4, 6, 8 and 10 Gy. Meanwhile, the other part of cells were exposed to the same doses by ⁶⁰Co at dose rate of 2.21 Gy/min. After irradiation, the cells were stained by trypan blue to measure the cellular mortality rate and to compare the changes along with plating times of 12, 24, 48 and 72 h after 4 Gy.The colonies were counted to obtain the plating efficiencies by colony-forming assay and the cell surviving fraction was calculated to plot cell survival curves, and RBE of ¹²⁵I seeds relative to ⁶⁰Co was determined. Results The cell death rate for continuous low-dose-rate (LDR) irradiation by ¹²⁵I seeds was greater than ⁶⁰Co at the same doses above or equal to 4 Gy. After 4 Gy irradiation, the cellular mortality rates were increased with times. The difference was significant between ¹²⁵I seeds and ⁶⁰Co. The survival fractions of ¹²⁵I were lower than those of ⁶⁰Co, and the RBE of ¹²⁵I relative to ⁶⁰Co was determined to be 1.45. Conclusion The cell-killing effects for continuous low-dose-rate (LDR) irradiation by ¹²⁵I seeds are greater than acute high-dose-rate of ⁶⁰Co.