| Autor: |
Luo WR; Department of Radiology, Chung Shan Medical University Hospital, Taichung, Taiwan., Chen FH; Department of Medical Imaging and Radiological Sciences, Chang Gung University, Kweishan, Taiwan.; Radiation Biology Research Center, Institute for Radiological Research, Chang Gung University/Chang Gung Memorial Hospital, Taoyuan, Taiwan.; Department of Radiation Oncology, Chang Gung Memorial Hospital-Linkou Branch, Taoyuan, Taiwan., Huang RJ; Department of Radiology, Chung Shan Medical University Hospital, Taichung, Taiwan.; Department of Medical Imaging and Radiological Sciences, Chung Shan Medical University, Taichung, Taiwan., Chen YP; Department of Radiology, Taipei Manicipal Wan-Fang Hospital, Taipei Medical University, Taipei, Taiwan., Hsiao YY; Department of Radiology, Chung Shan Medical University Hospital, Taichung, Taiwan.; Department of Medical Imaging and Radiological Sciences, Chung Shan Medical University, Taichung, Taiwan. |
| Abstrakt: |
Purpose: This study evaluated the DNA double strand breaks (DSBs) induced by indirect actions and its misrepairs to estimate the relative biological effectiveness (RBE) of proton beams. Materials and methods: From experimental data, DSB induction was evaluated in cells irradiated by 62 MeV proton beams in the presence of dimethylsulphoxide (DMSO) and under hypoxic conditions. The DNA damage yields for calculating the RBE were estimated using Monte Carlo Damage Simulation (MCDS) software. The repair outcomes (correct repairs, mutations and DSB conversions) were estimated using Monte Carlo Excision Repair (MCER) simulations. Results: The values for RBE of 62 MeV protons (LET = 1.051 keV/μm) for DSB induction and enzymatic DSB under aerobic condition (21% O 2 ) was 1.02 and 0.94, respectively, as comparing to 60 Co γ-rays (LET = 2.4 keV/μm). DMSO mitigated the inference of indirect action and reduced DSB induction to a greater extent when damaged by protons rather than γ-rays, resulting in a decreased RBE of 0.86. DMSO also efficiently prevented enzymatic DSB yields triggered by proton irradiation and reduced the RBE to 0.83. However, hypoxia (2% O 2 ) produced a similar level of DSB induction with respect to the protons and γ-rays, with a comparable RBE of 1.02. Conclusions: The RBE values of proton beams estimated from DSB induction and enzymatic DSB decreased by 16% and 12%, respectively, in the presence of DMSO. Our findings indicate that the overall effects of DSB induction and enzymatic DSB could intensify the tumor killing, while alleviate normal tissue damage when indirect actions are effectively interrupted. |
