Institute of Radiation Protection, Helmholtz Zentrum München-German Research Center for Environmental Health (GmbH), D-85764 Neuherberg, Germany.
Health Phys. 2010 Oct;99(4):503-10. doi: 10.1097/HP.0b013e3181c479bf.
The current dose coefficients for internal dose assessment of occupationally exposed persons and the general public were derived using the methodology of the International Commission on Radiological Protection (ICRP), which is similar to the Medical Internal Radiation Dose (MIRD)-type methodology. One component of this methodology is the mathematical representation of the human body (so-called MIRD-type phantoms) developed at the Oak Ridge National Laboratory for calculations of photon specific absorbed fractions (SAFs). Concerning the beta emissions, it is assumed in general that they irradiate only the organ where the radionuclide resides, whereas for walled organs, a fixed fraction of the emitted energy is absorbed within the wall. For the active marrow and bone surface targets, absorbed fractions were explicitly provided in ICRP Publication 30. The ICRP Publications 66 and 100 contain further detailed energy-dependent absorbed fraction data for the airways and the segments of the alimentary tract. In the present work, the voxel phantoms representing the reference male and female adults, recently developed at the Helmholtz Zentrum München-German Research Center for Environmental Health (HMGU) in collaboration with the Task Group DOCAL of ICRP Committee 2, were used for the Monte Carlo computation of photon as well as electron SAFs. These voxel phantoms, being constructed from computed tomography (CT) scans of individuals, are more realistic in shape and location of organs in the body than the mathematical phantoms; therefore, they provide photon SAFs that are more precise than those stemming from mathematical phantoms. In addition, electron SAFs for solid and walled organs as well as tissues in the alimentary tract, the respiratory tract, and the skeleton were calculated with Monte Carlo methods using these phantoms to complement the data of ICRP Publications 66 and 100 that are confined to self-irradiation. The SAFs derived for photons and electrons are then used to calculate the dose coefficients of the beta emitters 141Ce, 144Ce, 95Zr, and 90Sr. It is found that the differences of the dose coefficients due to the revised SAFs are much larger for injection and ingestion than for inhalation. The equivalent doses for colon and ingestion with the new voxel-based SAFs are significantly smaller than the values with the MIRD-type photon SAFs and simplifying assumptions for electrons. For lungs and inhalation, no significant difference was observed for the equivalent doses, whereas for injection and ingestion, an increase of the new values is observed.
当前用于评估职业暴露人员和公众内照射剂量的剂量系数是使用国际辐射防护委员会（ICRP）的方法推导的，该方法类似于医学内照射剂量（MIRD）型方法。该方法的一个组成部分是人体的数学表示（所谓的 MIRD 型体模），由橡树岭国家实验室开发，用于计算光子特定吸收分数（SAF）。对于β发射，一般假设它们仅照射放射性核素所在的器官，而对于有壁器官，发射能量的固定分数在壁内被吸收。对于活性骨髓和骨表面靶标，ICRP 出版物 30 中明确提供了吸收分数。ICRP 出版物 66 和 100 包含了空气通道和消化道段进一步详细的能量依赖吸收分数数据。在本工作中，最近由慕尼黑亥姆霍兹环境健康中心（HMGU）与 ICRP 委员会 2 的 DOCAL 工作组合作开发的代表参考男性和女性成年人的体素体模被用于光子和电子 SAF 的蒙特卡罗计算。这些体素体模是由个体的计算机断层扫描（CT）扫描构建的，在身体器官的形状和位置上比数学体模更真实，因此提供的光子 SAF 比数学体模更精确。此外，使用这些体模通过蒙特卡罗方法计算了固体和有壁器官以及消化道、呼吸道和骨骼组织的电子 SAF，以补充仅限于自照射的 ICRP 出版物 66 和 100 的数据。然后，将推导的光子和电子 SAF 用于计算β发射体 141Ce、144Ce、95Zr 和 90Sr 的剂量系数。结果发现，由于修正后的 SAF，注射和摄入的剂量系数差异比吸入的要大得多。使用新的基于体素的 SAF，对于结肠和摄入，当量剂量明显小于使用 MIRD 型光子 SAF 和电子简化假设的值。对于肺和吸入，观察到等效剂量没有显著差异，而对于注射和摄入，观察到新值的增加。
