Zaragoza Francisco J, Eichmann Marion, Flühs Dirk, Timmermann Beate, Brualla Lorenzo
Faculty of Medicine, University of Duisburg-Essen, Essen, Germany.
Fakultät Physik, Technische Universität Dortmund, Dortmund, Germany.
Ocul Oncol Pathol. 2020 Oct;6(5):353-359. doi: 10.1159/000508113. Epub 2020 Jul 20.
BACKGROUND/AIMS: The aim of this work is to compare Monte Carlo simulated absorbed dose distributions obtained from Ru eye plaques, whose heterogeneous emitter distribution is known, with the common homogeneous approximation. The effect of these heterogeneities on segmented structures at risk is analyzed using an anthropomorphic phantom.
The generic CCA and CCB, with a homogeneous emitter map, and the specific CCA1364 and CCB1256 Ru eye plaques are modeled with the Monte Carlo code PENELOPE. To compare the effect of the heterogeneities in the segmented volumes, cumulative dose-volume histograms are calculated for different rotations of the aforementioned plaques.
For the cornea, the CCA with the equatorial placement yields the lowest absorbed dose rate while for the CCA1364 in the same placement the absorbed dose rate is 33% higher. The CCB1256 with the hot spot oriented towards the cornea yields the maximum dose rate per unit of activity while it is 44% lower for the CCB.
Dose calculations based on a homogeneous distribution of the emitter substance yield the lowest absorbed dose in the analyzed structures for all plaque placements. Treatment planning based on such calculations may result in an overdose of the structures at risk.
背景/目的：本研究旨在将已知发射体分布不均匀的钌眼敷贴器通过蒙特卡洛模拟得到的吸收剂量分布，与常用的均匀近似方法进行比较。使用人体模型分析这些不均匀性对有风险的分割结构的影响。
使用蒙特卡洛代码PENELOPE对具有均匀发射体映射的通用CCA和CCB，以及特定的CCA1364和CCB1256钌眼敷贴器进行建模。为了比较分割体积中不均匀性的影响，针对上述敷贴器的不同旋转角度计算累积剂量-体积直方图。
对于角膜，赤道放置的CCA产生的吸收剂量率最低，而相同放置的CCA1364的吸收剂量率高33%。热点朝向角膜的CCB1256每单位活度产生的剂量率最高，而CCB则低44%。
对于所有敷贴器放置情况，基于发射体物质均匀分布的剂量计算在分析结构中产生的吸收剂量最低。基于此类计算的治疗计划可能导致有风险结构的剂量过量。
