Yamauchi M, Ishikawa M, Hoshi M
International Radiation Information Center, Research Institute for Radiation Biology and Medicine, Hiroshima University, Minami-ku, Hiroshima 734-8553, Japan.
Med Phys. 2005 Jan;32(1):85-92. doi: 10.1118/1.1829248.
Computational models of human anatomy, along with Monte Carlo radiation transport simulations, have been used by Snyder et al. [MIRD Pamphlet No. 5, revised (The Society of Nuclear Medicine, New York, 1978)], Cristy and Eckerman [ORNL/TM-8381/VI, Oak Ridge National Laboratory, Oak Ridge, TN (1987)] and Zubal et al. [Med. Phys. 21, 299-302 (1994)] to estimate internal organ doses from internal and external radiation sources. These were created using physiological data from Caucasoid subjects but not from other races. There is a need for research to determine whether the obvious differences from the Caucasoid anatomy make these models unsuitable for estimating the absorbed dose in other races such as the Mongoloid. We used the cranial region of the adult Japanese male to represent the Mongoloid race. This region contains organs that are highly sensitive to radiation. The cranial region of a physical phantom produced by KYOTO KAGAKU Co., LTD. using numerical data from a Japanese Reference Man [Tanaka, Nippon Acta. Radiol. 48, 509-513 (1988)] was used to supply the data for the geometry of a stylized computational model. Our computational model was constructed with equations rather than voxel-based, in order to deal with as small a number of parameters as possible in the computer simulation experiment. The accuracy of our computational model was checked by comparing simulated experimental results obtained with MCNP4C with actual doses measured with thermoluminescence dosimeters (TLDs) inside the physical phantom from which our computational model was constructed. The TLDs, whose margin of error is less than +/-10%, were arranged at six positions. Co-60 was used as the radiation source. The irradiated dose was 2 Gy in terms of air kerma. In the computer simulation experiments, we used our computational model and Cristy's computational model, whose component data are those of the tissue substitute materials and of the human body as published in ICRU Report 46. The observed absorbed dose values (Gy) at all six points were calculated as the percentage difference between MCNP4C simulation and the TLDs. In our computational model, the average values of all the percentage differences were 6.0+/-4.0% (tissue substitute materials) and 7.6+/-6.6% (ICRU Report 46), respectively. In Cristy's model, the corresponding values were 20.4+/-3.8% (tissue substitute materials) and 21.0+/-4.1% (ICRU Report 46), respectively. Considering the margin of error in the radiation sensitivity of the TLDs, this study validates our computational model as a test object for radiation dosimetry studies.
斯奈德等人[《核医学学会手册第5号，修订版》（纽约核医学学会，1978年）]、克里斯蒂和埃克曼[《橡树岭国家实验室报告ORNL/TM - 8381/VI》，田纳西州橡树岭橡树岭国家实验室（1987年）]以及祖巴尔等人[《医学物理》21卷，299 - 302页（1994年）]利用人体解剖学计算模型以及蒙特卡罗辐射传输模拟来估算来自体内和体外辐射源的内部器官剂量。这些模型是使用高加索人种受试者的生理数据创建的，而非其他种族。有必要开展研究以确定与高加索人种解剖结构的明显差异是否使得这些模型不适用于估算其他种族（如蒙古人种）的吸收剂量。我们使用成年日本男性的颅骨区域来代表蒙古人种。该区域包含对辐射高度敏感的器官。京都化学株式会社利用来自日本参考人的数值数据[田中，《日本放射学学报》48卷，509 - 513页（1988年）]制作的物理模型的颅骨区域，被用于为一个简化计算模型的几何结构提供数据。我们的计算模型是用方程构建的，而非基于体素，以便在计算机模拟实验中处理尽可能少的参数。通过将用MCNP4C获得的模拟实验结果与在构建我们计算模型所依据的物理模型内部用热释光剂量计（TLD）测量的实际剂量进行比较，来检验我们计算模型的准确性。误差范围小于±10%的TLD被布置在六个位置。使用钴 - 60作为辐射源。以空气比释动能计，照射剂量为2 Gy。在计算机模拟实验中，我们使用了我们的计算模型以及克里斯蒂的计算模型，其组成数据是ICRU报告46中公布的组织替代材料和人体的数据。将MCNP4C模拟与TLD之间的百分比差异计算为在所有六个点处观察到的吸收剂量值（Gy）。在我们的计算模型中，所有百分比差异的平均值分别为6.0±4.0%（组织替代材料）和7.6±6.6%（ICRU报告46）。在克里斯蒂的模型中，相应的值分别为20.4±3.8%（组织替代材料）和21.0±4.1%（ICRU报告46）。考虑到TLD辐射敏感性的误差范围，本研究验证了我们的计算模型可作为辐射剂量学研究中的测试对象。
