Lee Choonik, Lee Choonsik, Bolch Wesley E
Department of Nuclear & Radiological Engineering, University of Florida, Gainesville, FL 32611, USA.
Phys Med Biol. 2006 Sep 21;51(18):4663-88. doi: 10.1088/0031-9155/51/18/014. Epub 2006 Sep 4.
This present study investigates the anatomical realism of conventional stylized models of children by comparing organ dose conversion coefficients for the ORNL paediatric phantom series with those determined in the UF (University of Florida) voxel paediatric phantoms. The latter includes whole-body models of a 9 month male, 4 year female, 8 year female, 11 year male and a 14 year male. Of these phantoms, the 1 year, 5 year and 10 year ORNL phantoms, and 9 month male, 4 year female and 11 year male UF voxel phantoms were selected for side-by-side comparisons under idealized external photon irradiation. Organ absorbed dose per unit air kerma (Gy/Gy) for various radiosensitive organs and tissues were calculated for monoenergetic photons over the energy range of 15 keV to 10 MeV and for six irradiation geometries: anterior-posterior (AP), posterior-anterior (PA), right lateral (RLAT), left lateral (LLAT), rotational (ROT) and isotropic (ISO). Differences in organ dose conversion coefficients for the gonads, bone marrow, colon, lung and stomach, to which prominent tissue weighting factors are assigned, were depicted and analysed. Two major causes of observed differences were suggested: differences in organ shape and position and the differences in tissue shielding by overlying tissue regions within the phantoms. Significant discrepancies caused by anatomical differences between the two types of phantoms are also reported for several organs, and in particular, the thyroid and urinary bladder. The results of this study suggest that the paediatric series of ORNL phantoms also have less realistic internal organ and body anatomy and that dose conversion coefficients from these stylized phantoms should be re-evaluated using paediatric voxel phantoms.
本研究通过比较橡树岭国家实验室（ORNL）儿科体模系列的器官剂量转换系数与佛罗里达大学（UF）体素儿科体模所确定的系数，来研究传统儿童风格化模型的解剖学真实性。后者包括一名9个月大男性、一名4岁女性、一名8岁女性、一名11岁男性和一名14岁男性的全身模型。在这些体模中，选择1岁、5岁和10岁的ORNL体模，以及9个月大男性、4岁女性和11岁男性的UF体素体模，在理想化的外部光子照射下进行并排比较。计算了15 keV至10 MeV能量范围内的单能光子以及六种照射几何条件下（前后位（AP）、后前位（PA）、右侧位（RLAT）、左侧位（LLAT）、旋转位（ROT）和各向同性位（ISO））各种辐射敏感器官和组织的单位空气比释动能器官吸收剂量（Gy/Gy）。描绘并分析了分配有显著组织权重因子的性腺、骨髓、结肠、肺和胃的器官剂量转换系数差异。提出了观察到的差异的两个主要原因：器官形状和位置的差异以及体模内覆盖组织区域对组织屏蔽的差异。还报告了两种类型体模之间的解剖学差异导致的几个器官的显著差异，特别是甲状腺和膀胱。本研究结果表明，ORNL儿科体模系列的内部器官和身体解剖结构也不太逼真，这些风格化体模的剂量转换系数应使用儿科体素体模重新评估。
