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目的模拟临床调强适形放疗的照射模式对人大肠癌细胞系HT-29进行生物效应变化的初步研究。方法采用指数生长期的HT-29细胞制成单细胞悬液,于接种后12 h内进行不同模式和剂量的照射。分成3个照射组:(1)急速照射组(包括0、1、2、3、5、71、0 Gy共7个剂量点),剂量点的照射完成时间为0~5 min,剂量率为6 Gy/min;(2)IMRT照射模式组(包括15 min完成照射组及30 min完成照射组),剂量率同上,每组所含照射剂量点同急速照射组,其中15 min和30 min照射组指各剂量点完成照射时间分别是15 min和30 min。采用成克隆分析法计算存活分数,运用多靶单击数学模型拟合曲线,求出D0、Dq等参数值。结果急速照射组1、5 min照射组和30 min照射组的Dq值分别为1.54、1.74和1.72 Gy;D0值分别为0.82、0.89和1.00 Gy;SF2分别为0.448、0.548和0.558。结论IM-RT模式下随分次照射时间的延长,相对剂量率降低,从而导致生物效应下降。
Objective To study the biological effects of radiation-modulated conformal radiation therapy on human colorectal cancer cell line HT-29. Methods Exponentially growing HT-29 cells were used to make single cell suspension and irradiated with different modes and doses within 12 h after inoculation. Divided into three groups: (1) rapid irradiation group (including 0, 1, 2, 3, 5, 71 and 0 Gy for a total of 7 dose points), dose point irradiation time of 0 ~ 5 min, 6 Gy / min; (2) IMRT irradiation group (including 15 min irradiation group and 30 min irradiation group), the dose rate was the same as above, Group refers to the completion of the irradiation time of each dose point is 15 min and 30 min. Survival scores were calculated by clonality analysis, and the curves were fitted by using multi-target click mathematic models to obtain the values of D0 and Dq. Results The values of Dq were 1.54, 1.74 and 1.72 Gy in 1.5 min irradiation group and 30 min irradiation group, respectively; the D0 values were 0.82, 0.89 and 1.00 Gy respectively for SFI group and 0.448, 0.548 and 0.558 for SFI group. Conclusion With the extension of fractional irradiation time in IM-RT mode, the relative dose rate decreases, which leads to the decrease of biological effect.