Many studies in biomedical research and various allied fields, in which cells or laboratory animals are exposed to radiation, rely on adequate radiation dose standardization for reproducibility and comparability of biological data. Due to increasing concerns regarding international terrorism, the use of radioactive isotopes has recently been met with enhanced security measures. Thus, a growing number of researchers have considered transferring their studies from gamma-ray to kilovoltage X-ray irradiators. Current commercially-available X-ray biological irradiators produce radiation beams with reasonable field geometry and overall dose-homogeneity; however, they operate over a wide range of different energies, both between different models and for a specific unit as well. As a result, the contribution from Compton scattering and the photoelectric effect also varies widely between different irradiators and different beam qualities. The photoelectric effect significantly predominates at the relatively low X-ray energies in which these irradiators operate. Consequently, a higher dose is delivered to bony tissues and the adjacent hematopoietic cells of the bone marrow. The increase in average radiation absorbed dose to the bone marrow compartment of the mouse can be as high as 30%, causing higher hematological sensitivity of animals when exposed to kilovoltage X rays. Adjusting the radiation dose to simply provide biological equivalency is complicated due to steep dose gradients within the marrow tissue and the qualitatively different outcomes depending on the spatial location of critical stem and progenitor populations in relationship to bone. These concerns may be practically addressed by efforts to implement X rays of the highest possible beam energy and penetration and increased awareness that radiation damage to hematopoietic cells will not be identical to data obtained from standard 137Cs gamma rays.

中文翻译：

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从伽马射线到X射线的过渡，以进行可比的生物医学研究辐射：能量问题。

生物医学研究和各个相关领域中的许多研究（其中细胞或实验动物都受到辐射照射）依赖于足够的辐射剂量标准化来实现生物数据的可重复性和可比性。由于对国际恐怖主义的日益关注，最近已通过加强安全措施来解决放射性同位素的使用问题。因此，越来越多的研究人员考虑将他们的研究从伽马射线转移到千伏X射线辐射器。当前的市售X射线生物辐射器产生的辐射束具有合理的场几何形状和总体剂量均匀性。但是，它们在各种不同的能量上运行，无论是在不同型号之间还是在特定设备上。结果是，康普顿散射和光电效应的贡献在不同的照射器和不同的光束质量之间也有很大差异。在这些辐射器工作的相对较低的X射线能量下，光电效应明显占优势。因此，较高的剂量被递送至骨髓的骨组织和相邻的造血细胞。暴露于小鼠骨髓腔的平均辐射吸收剂量可高达30％，当暴露于千伏X射线时，会引起动物更高的血液学敏感性。由于骨髓组织内陡峭的剂量梯度以及取决于关键茎和祖细胞与骨骼的关系的空间位置，在质量上会有不同的结果，因此调整辐射剂量以简单地提供生物学等效性非常复杂。通过努力实现可能的最高射线束能量和穿透力的X射线，以及提高人们对造血细胞的辐射损害将与从标准137Cs伽玛射线获得的数据不同的认识，可以切实解决这些问题。