Jönsson Lena, Liu Xiaowei, Jönsson Bo-Anders, Ljungberg Michael, Strand Sven-Erik
Department of Radiation Physics, The Jubileum Institute, Lund University, Lund University Hospital, Lund, Sweden.
J Nucl Med. 2002 Dec;43(12):1657-64.
Current internal radiation dosimetry models for the small intestine, and for most walled organs, lack the ability to account for the activity uptake in the intestinal wall. In existing models the cross-dose from nearby loops of the small intestine is not taken into consideration. The aim of this investigation was to develop a general model for calculating the absorbed dose to the radiation-sensitive cells in the small intestinal mucosa from radionuclides located in the small intestinal wall or contents.
A model was developed for calculation of the self-dose and cross-dose from activity in the intestinal wall or contents. The small intestine was modeled as a cylinder with 2 different wall thicknesses and with an infinite length. Calculations were performed for various mucus thicknesses. S values were calculated using the EGS4 Monte Carlo simulation package with the PRESTA algorithm and the simulation results were integrated over the depth of the radiosensitive cells. The cross-organ dose was calculated by summing the dose contributions from other intestinal segments. Calculations of S values for self-dose and cross-dose were made for monoenergetic electrons, 0.050-10 MeV, and for the radionuclides (99m)Tc, (111)In, (131)I, (67)Ga, (90)Y, and (211)At.
The self-dose S value from activity located in the small intestinal wall is considerably greater than the S values for self-dose from the contents and the cross-dose from wall and contents except for high electron energies. For all radionuclides investigated and for electrons 0.10-0.20 MeV and 8-10 MeV in energy, the cross-dose from activity in the contents is higher than the self-dose from the contents. The mucus thickness affects the S value when the activity is located in the contents.
A dosimetric model for the small intestine was developed that takes into consideration the localization of the radiopharmaceutical in the intestinal wall or in the contents. It also calculates the contribution from self-dose and cross-dose. With this model, more accurate calculations of absorbed dose to radiation-sensitive cells in the intestine are possible.
目前用于小肠以及大多数有壁器官的内照射剂量学模型，缺乏考虑肠壁内放射性摄取的能力。在现有模型中，未考虑来自小肠附近肠袢的交叉剂量。本研究的目的是开发一种通用模型，用于计算位于小肠壁或肠内容物中的放射性核素对小肠黏膜辐射敏感细胞的吸收剂量。
开发了一个模型，用于计算来自肠壁或肠内容物中放射性活度的自剂量和交叉剂量。小肠被建模为一个具有两种不同壁厚且长度无限的圆柱体。针对各种黏液厚度进行了计算。使用EGS4蒙特卡罗模拟软件包和PRESTA算法计算S值，并将模拟结果在辐射敏感细胞深度上进行积分。通过汇总来自其他肠段的剂量贡献来计算跨器官剂量。针对能量为0.050 - 10 MeV的单能电子以及放射性核素（99m）Tc、（111）In、（131）I、（67）Ga、（90）Y和（211）At，计算了自剂量和交叉剂量的S值。
位于小肠壁中的放射性活度产生的自剂量S值，除了高电子能量情况外，明显大于来自肠内容物的自剂量S值以及来自肠壁和肠内容物的交叉剂量S值。对于所有研究的放射性核素以及能量为0.10 - 0.20 MeV和8 - 10 MeV的电子，来自肠内容物中放射性活度的交叉剂量高于来自肠内容物的自剂量。当放射性活度位于肠内容物中时，黏液厚度会影响S值。
开发了一种小肠剂量学模型，该模型考虑了放射性药物在肠壁或肠内容物中的定位。它还计算了自剂量和交叉剂量的贡献。利用该模型，可以更准确地计算小肠中辐射敏感细胞的吸收剂量。
