Petoussi-Henss Nina, Bolch W E, Zankl M, Sgouros G, Wessels B
GSF-National Research Center for Environment and Health, Institute of Radiation Protection, Ingolstaedter Landstr. 1, 85764 Neuherberg, Germany.
Radiat Prot Dosimetry. 2007;127(1-4):192-6. doi: 10.1093/rpd/ncm270. Epub 2007 Jun 14.
The Medical Internal Radiation Dose Committee (MIRD) formalism assumes reference mass values for the organs (source and target) and the total body. MIRD publication 11 provides guidance on how patient-specific scaling of reference radionuclide S-values are to be performed for the electron component of the emission spectrum. However, guidance on patient-specific scaling of the photon contributions to the S-value is given only for those cases where the source and target organs are either far apart or are the same. The photon component of the S-value is derived from photon-Specific Absorbed Fractions (SAFs). These are obtained by Monte Carlo calculation of photon transport. The objective of this work is to verify the MIRD 11 guidance and to examine the relationship between photon SAFs and source/target organ mass when the conditions listed above do not apply. Furthermore, the scaling for photon cross-dose to distributed organs is at present not defined due to lack of data for models other than the reference model. The validity of mass scaling for cross irradiation from near and distant photons sources, especially for Red Bone Marrow (RBM) as a target tissue is also investigated. This is achieved by comparing Monte Carlo-derived SAFs for different source organs to RBM across the GSF voxel phantom series. The results show that, for photon energies greater than 100 keV, the SAF of most source organs to RBM need not be corrected for target mass (error < 5%). In contrast to the results obtained for well-defined source organs, the SAF for RBM irradiating RBM gives a deviation of up to 16% across the different GSF voxel phantoms.
医学内照射剂量委员会（MIRD）的形式体系假定了器官（源器官和靶器官）以及全身的参考质量值。MIRD第11号出版物提供了关于如何针对发射光谱的电子成分对参考放射性核素S值进行患者特异性缩放的指导。然而，仅针对源器官和靶器官相距很远或相同的那些情况，给出了光子对S值贡献的患者特异性缩放指导。S值的光子成分源自光子特定吸收分数（SAFs）。这些通过光子传输的蒙特卡罗计算获得。这项工作的目的是验证MIRD 11的指导，并在上述条件不适用时检查光子SAFs与源/靶器官质量之间的关系。此外，由于缺乏除参考模型之外的模型数据，目前尚未定义对分布器官的光子交叉剂量的缩放。还研究了来自近距和远距光子源的交叉照射的质量缩放的有效性，特别是将红骨髓（RBM）作为靶组织的情况。这是通过比较GSF体素模型系列中不同源器官对RBM的蒙特卡罗衍生SAFs来实现的。结果表明，对于能量大于100 keV的光子，大多数源器官对RBM的SAF无需针对靶质量进行校正（误差<5%）。与针对明确源器官获得的结果相反，RBM照射RBM的SAF在不同的GSF体素模型中给出了高达16%的偏差。
