Washington State University Tri-Cities, Richland, Washington 99354, USA.
Radiat Res. 2011 Jan;175(1):113-8. doi: 10.1667/RR2339.1. Epub 2010 Nov 10.
Monte Carlo simulation of electrons stopping in liquid water was used to model the penetration and quality of electron-beam irradiation incident on the full-thickness EpiDerm™ skin model (EpiDermFT™ MatTek, Ashland, VA). This 3D tissue model has a fully developed basement membrane separating an epidermal layer of keratinocytes in various stages of differentiation from a dermal layer of fibroblasts embedded in collagen. The simulations were motivated by a desire to selectively expose the epidermal layer to low-linear energy transfer (LET) radiation in the presence of a nonirradiated dermal layer. The variable-energy electron microbeam at the Pacific Northwest National Laboratory (PNNL) was used as a model of device characteristics and irradiation geometry. At the highest beam energy available (90 keV), we estimate that no more than a few percent of the beam energy will be deposited in the dermal layer. Energy deposition spectra were calculated for 10-µm-thick layers near the 10th, 50th and 90th percentiles of penetration by the 90 keV electron beam. Bimodal spectra showed an increasing component of "stoppers" with increasing depth, which increases the probability of large energy deposition events. Nevertheless, screening by tissue above the layer of interest is the main factor determining energy deposited at a given depth.
利用电子在液体水中停止的蒙特卡罗模拟，对全厚度 EpiDerm™皮肤模型（EpiDermFT™ MatTek，阿什兰，弗吉尼亚州）中电子束辐照的穿透和质量进行建模。该 3D 组织模型具有完全发育的基底膜，将处于不同分化阶段的角质形成细胞的表皮层与嵌入胶原蛋白中的成纤维细胞的真皮层分开。模拟的动机是希望在未辐照的真皮层存在下，选择性地使表皮层暴露于低线性能量转移（LET）辐射下。太平洋西北国家实验室（PNNL）的可变能电子微束被用作器件特性和辐照几何形状的模型。在可用的最高束能量（90 keV）下，我们估计，在真皮层中沉积的束能量不会超过百分之几。对于通过 90 keV 电子束穿透的第 10、50 和 90 个百分位数附近的 10-µm 厚的层，计算了能量沉积谱。双模态谱显示，随着深度的增加，“阻止器”的成分不断增加，这增加了大能量沉积事件的可能性。然而，位于感兴趣层上方的组织的屏蔽是决定给定深度处沉积的能量的主要因素。
