Mills Caitlin E, Thome Christopher, Koff David, Andrews David W, Boreham Douglas R
a Department of Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, Ontario, Canada.
Radiat Res. 2015 Jan;183(1):42-51. doi: 10.1667/RR13821.1. Epub 2014 Dec 23.
Mammography is used to screen a large fraction of the population for breast cancer, and mammography quality X rays are speculated to be more damaging than the higher energy X rays used for other diagnostic procedures. The radiation dose delivered to breast cells as a result of these screening exposures may be a concern. The purpose of this current study was to determine the relative biological effectiveness (RBE) of low-energy mammography X rays for radiation-induced DNA double-strand breaks evaluated using a highly sensitive automated 53BP1 assay. Automation of the 53BP1 assay enabled the quantification and analysis of meaningful image-based features, including foci counting, within the cell nuclei. Nontumorigenic, human breast epithelial MCF-10A cells were irradiated in the low-dose range with approximately 3-30 mGy of 29 kVp mammography X rays or (137)Cs (662 keV) gamma rays. The induction and resolution of the 53BP1 foci did not differ significantly between exposures to (137)Cs gamma rays and 29 kVp X rays. The RBE was calculated to be 1.1 with a standard deviation of 0.2 for the initial number of radiation-induced double-strand breaks. The radiation dose from a single mammogram did not yield a significant change in the number of detectable foci. However, analysis of additional features revealed subtle differences in the distribution of 53BP1 throughout the nuclei after exposure to the different radiation qualities. A single mammogram was sufficient to alter the distribution of 53BP1 within the nuclear area, but not into discrete foci, while a dose-matched gamma exposure was not sufficient to alter the distribution of 53BP1. Our results indicate that exposure to clinically relevant doses of low-energy mammography quality X rays does not induce more DNA double-strand breaks than exposure to higher energy photons.
乳房X线摄影术用于对很大一部分人群进行乳腺癌筛查，据推测，乳房X线摄影质量的X射线比用于其他诊断程序的更高能量X射线更具危害性。这些筛查性照射对乳腺细胞造成的辐射剂量可能令人担忧。本研究的目的是使用高度灵敏的自动化53BP1检测法，确定低能量乳房X线摄影X射线对辐射诱导的DNA双链断裂的相对生物效应（RBE）。53BP1检测法的自动化能够对细胞核内基于图像的有意义特征进行量化和分析，包括病灶计数。用约3 - 30 mGy的29 kVp乳房X线摄影X射线或（137）Cs（662 keV）γ射线在低剂量范围内照射非致瘤性人乳腺上皮MCF - 10A细胞。在暴露于（137）Csγ射线和29 kVp X射线之间，53BP1病灶的诱导和消退没有显著差异。对于辐射诱导的双链断裂的初始数量，计算得出的RBE为1.1，标准差为0.2。单次乳房X线摄影的辐射剂量并未使可检测病灶数量产生显著变化。然而，对其他特征的分析揭示了在暴露于不同辐射质量后，53BP1在整个细胞核内分布的细微差异。单次乳房X线摄影足以改变53BP1在核区域内的分布，但不会形成离散病灶，而剂量匹配的γ射线照射不足以改变53BP1的分布。我们的结果表明，与暴露于更高能量光子相比，暴露于临床相关剂量的低能量乳房X线摄影质量X射线不会诱导更多的DNA双链断裂。
