α粒子微束定点照射--细胞的放射生物学效应及精确性分析

进行微束试验的关键是能够精确地控制照射的粒子数和将粒子准确地射入受照射位点.该研究通过对哥伦比亚大学单粒子微束装置在精确性、准确性以及各项指标的分析发现该装置可精确地控制照射粒子数,精确率为98.4%.同时,它可将α粒子准确地射入受照射位点,束半径为34,达到设计4的标准.在对细胞特定位点如细胞质照射上,粒子击中细胞质至少一个位点的概率为90%,在这一过程中的偶然核击中率,对大多数照射剂量(8个粒子)均小于0.8%.应用该微束装置的放射生物学研究发现单个α粒子仅导致大约20%的致死率,其存活率曲线类似于用常规照射获得的平均粒子存活曲线.诱变试验首次证实单个α粒子在AL细胞的CD59基因位点可诱导出比对照高出3倍数量的诱变子,诱变率随粒子数的增加而增加.这一结果不同于常规照射中,诱变率在高剂量照射后下降的结论.

TARGETED MICROBEAM IRRADIATION: STUDIES ON THE RADIOLOGICALEFFECTS AND THE ACCURACY OF PARTICLE IRRADIATION

The key to doing microbeam studies is to precisely control and accurately deliver the counted number of particles to a target position. By studying the Columbia University single particle microbeam, this report shows that it can irradiate the targets with a defined number of or particles, and the collimation of beam size according to the resolution of 20 a particles is ~3~4um which is better than the designed index. Besides, it can be used for cytoplasmic irradiation with a hitting probability nearly 90% and the odds to hitting nucleus during this process is less than 0.8% for most doses. Radiological studies using this facility found that only 20% of irradiated cells were killed by a single a particle, and the dose response curve for nuclear irradiation with exact number of particles was not significantly different from the curve obtained using average particle traversals of broad-field exposure. Tile mutation data in microbeam studies provide the first demonstration that a single or particle traversal induced mutations in A_L coils at a level 3X greater than the background value, and the mutation yield increased in a dose dependent manlier. This results was quite different from the data obtained from broad field exposure which showed that at high doses, the mutation frequencies decreased.