In this work, we developed a DNA dosimeter, consisting of 4-kb DNA strands attached to magnetic streptavidin beads and labeled with fluorescein, to detect double-strand breaks (DSBs). The purpose here was to evaluate whether the DNA dosimeter readings reflect the relative biological effects of 160 kVp and 6 MV X rays. AVarian 600 C/D linac (6 MV) and a Faxitron cabinet X-ray system (160 kVp), both calibrated using traceable methods, were used to deliver high- and low-energy photons, respectively, to DNA dosimeters and multiple cell lines (mNs-5, HT-22 and Daoy). The responses were fit versus dose, and were used to quantify the dose of low-energy photons that produced the same response as that of the high-energy photons, at doses of 3, 6 and 9 Gy. The equivalent doses were utilized to calculate the relative biological effectiveness (RBE_DSB and RBE_{cell survival}). Additionally, a neutral comet assay was performed to measure the amount of intracellular DNA DSB, and ultimately the RBE_{comet assay}. The results of this work showed 160-kVp photon RBE values and 95% confidence intervals of 1.12 ± 0.04 (mNS-5), 1.16 ± 0.06 (HT-22), 1.25 ± 0.09 (Daoy) and 1.21 ± 0.24 (DNA dosimeter) at 9 Gy and 1.32 ± 0.16 (comet assay) at 3 Gy. Within the current error, the DNA dosimeter measured RBE_DSB values in agreement with the RBE_{cell survival} and _assay from the cell survival and comet assay RBE_comet measurements. These results suggest that the DNA dosimeter can measure the changes in the radiobiological effects from different energy photons.

在这项工作中，我们开发了一种 DNA 剂量计，由附着在磁性链霉亲和素珠上并用荧光素标记的 4 kb DNA 链组成，用于检测双链断裂 (DSB)。这里的目的是评估 DNA 剂量计读数是否反映 160 kVp 和 6 MV X 射线的相对生物效应。 AVarian 600 C/D 直线加速器 (6 MV) 和 Faxitron 柜式 X 射线系统 (160 kVp) 均使用可追踪方法进行校准，分别用于向 DNA 剂量计和多个细胞系传递高能和低能光子（mNs-5、HT-22 和 Daoy）。响应与剂量相符，并用于量化低能光子的剂量，这些低能光子在 3、6 和 9 Gy 的剂量下产生与高能光子相同的响应。使用等效剂量来计算相对生物有效性（RBE _DSB和 RBE_{细胞存活率}）。此外，还进行了中性彗星测定来测量细胞内 DNA DSB 的量，并最终进行了 RBE_彗星测定。这项工作的结果显示，光子 RBE 值为 160-kVp，95% 置信区间为 1.12 ± 0.04 (mNS-5)、1.16 ± 0.06 (HT-22)、1.25 ± 0.09 (Daoy) 和 1.21 ± 0.24（DNA 剂量计） 9 Gy 和 3 Gy 1.32 ± 0.16（彗星测定）。在当前误差范围内，DNA剂量计测量的RBE _DSB值与_细胞存活和彗星_测定RBE_彗星测量的RBE细胞存活和测定一致。这些结果表明DNA剂量计可以测量不同能量光子的放射生物学效应的变化。