Mohammad Rafiei Mustafa, Parsaei Sara, Kaur Parminder, Singh K J, Büyükyıldız Mehmet, Kurudirek Murat
Faculty of Physics, Shahid Bahonar University of Kerman, Kerman, Iran.
Department of Physics, Guru Nanak Dev University, Amritsar, 143005, India.
Biomed Phys Eng Express. 2022 Jan 5;8(2). doi: 10.1088/2057-1976/ac428f.
The attenuation coefficients are important input values in estimating not only the dose and exposure in radiotherapy and medical imaging, but also in the proper design of photon shields. While studies are widely available above 1 keV, the attenuation coefficients of human tissues for photon energies less than 1 keV have not been studied yet. In this study, the attenuation coefficients of water and some human tissues were estimated for low energy photons using the MCNP6.1 code in the energy region 0.1 keV-1 keV. Mass attenuation coefficients were estimated at photon energies of 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950 and 1000 eV for water and ten human tissues (Soft, Breast, Lung, Bone, Brain, Eye lens, Ovary, Skin, Thyroid and Prostate). Results were compared with those available in literature and a fairly good agreement has been obtained. These data were then used to calculate the mean free path, half value layer, tenth value layer, effective atomic number and specific gamma-ray constant (useful for calculation of dose rate) as well. Moreover, for comparison the effective atomic number of the water has been obtained using the results of this work and using the data available in NIST database from 0.1 to 1 keV. In addition, the human tissues were compared with some tissue equivalent materials in terms of effective atomic number and specific gamma-ray constant to study the tissue equivalency from the results, the muscle-equivalent liquid with sucrose has been found to be the best tissue equivalent material for soft tissue, eye lens and brain with relative difference below 4.1%.
衰减系数不仅是估算放射治疗和医学成像中的剂量与照射量的重要输入值，也是光子屏蔽合理设计的重要输入值。虽然在1 keV以上有大量研究，但对于能量低于1 keV的光子，人体组织的衰减系数尚未得到研究。在本研究中，使用MCNP6.1代码在0.1 keV - 1 keV能量区域估算了水和一些人体组织对低能光子的衰减系数。在光子能量为100、150、200、250、300、350、400、450、500、550、600、650、700、750、800、850、900、950和1000 eV时，估算了水和十种人体组织（软组织、乳腺、肺、骨、脑、晶状体、卵巢、皮肤、甲状腺和前列腺）的质量衰减系数。将结果与文献中的结果进行了比较，获得了相当好的一致性。然后，这些数据还用于计算平均自由程、半值层、十分之一值层、有效原子序数和比释伽马射线常数（对剂量率计算有用）。此外，为了进行比较，利用本工作的结果以及NIST数据库中0.1至1 keV的可用数据获得了水的有效原子序数。此外，根据有效原子序数和比释伽马射线常数，将人体组织与一些组织等效材料进行了比较，以研究组织等效性。结果发现，含蔗糖的肌肉等效液体是软组织、晶状体和脑的最佳组织等效材料，相对差异低于4.1%。
