Studies On Evaluation Models For Biological Effects Of Heavy-ion Radiation

With the development of nuclear technology and its extensive applications in many fields, ionizing radiation has become an important environmental factor in human life. In addition, the rapid development of deep-space exploration projects in international and domestic aerospace field also involve the problem of how astronauts to confront the ionizing radiation in deep-space missions. In all kinds of ionizing radiation, heavy-ion radiation can cause severe biological effects. In order to investigate the complex characteristics of radiation effects and reveal the origin of radiation-induced biological effects, the physical interacting process between radiation and biological structure should be examined in the microscopic level of cells and macromolecules.The target theory plays a critical role in quantitatively studying radiation biological effects. The traditional target theory assumes that radiation damage is a random process, which the distribution of hits should follow a Poisson distribution. On average, the probability of a particle hitting the target is far less than that of missing it for radiation with lower energy and lower linear energy transfer (LET). So, the traditional target theory can be used to explain the damage effects of biological macromolecules or cells exposed to the radiation environment with lower energy and LET, such as X-ray and gamma ray. However, heavy-ions, such as a particles, carbon ions, iron ions, generally have higher energy and LET. On average, the probability of a particle hitting a cell or macromolecule is comparable to that of missing it. In this way, the target theory based on the Gaussian distribution should be more suitable to study the biological effects of heavy-ion radiation.In this paper, we proposed a target theory based on the Gaussian distribution and discussed the application conditions of the two target theories. The results show that the single-hit single-target model and multiple-hit single-target model based on the Gaussian distribution have no significant advantage compared with the target theory based on Poisson distribution. But the single-hit multiple-target model based on the Gaussian distribution fits well with experimental date than that of based on the Poisson distribution. In addition, the multiple-hit single-target model, which based on the Gaussian distribution or the Poisson distribution, may be inappropriate for studying biological effects of mammalian cells exposed to heavy-ion radiation. In contrast, single hit multiple-target model, especially the model based on the Gaussian distribution, is more suitable for studying radiation biological effects of mammalian cells.