On the validity of the superposition principle in dose calculations for intracavitary implants with shielded vaginal colpostats.
On the validity of the superposition principle in dose calculations for intracavitary implants with shielded vaginal colpostats.
复制标题
叠加原理在带屏蔽阴道阴道植入物的腔内植入物剂量计算中的有效性。
DOI：
10.1118/1.1339224
复制
发表时间：
2001
期刊：
影响因子：
3.8
通讯作者：
Low,DA
中科院分区：
文献类型：
--
作者：
Markman,J;Williamson,JF;Dempsey,JF;Low,DA
腔内阴道施用器通常结合内部屏蔽以减少对膀胱和直肠的剂量。虽然已经广泛测量和计算了单个阴道的剂量分布，但这些研究忽略了对侧阴道或子宫内串联引起的剂量学扰动。近距离放射治疗中不均匀性的剂量效应对于基于剂量的植入物优化以及与替代模式（如调强放射治疗）的比较至关重要。我们使用蒙特卡罗计算对Fletcher-Suit-Delaware（FSD）低剂量率系统和microSelectron高剂量率远程后装系统的剂量分布进行了建模。我们已经评估了错误，相对于一个完整的施源器系统的基础上，在叠加计算的基础上预先计算的单屏蔽施源器剂量分布以及单未屏蔽源剂量分布的Monte Carlo模拟。误差在很大程度上主要由初级光子衰减决定，并且在屏蔽和串联之后最大。对于FSD施源器，施源器叠加显示的差异范围从高剂量（>曼彻斯特点A剂量）的平均2.6%到低剂量（>曼彻斯特点A剂量）的4.3%。
Intracavitary vaginal applicators typically incorporate internal shielding to reduce dose to the bladder and rectum. While dose distributions about a single colpostat have been extensively measured and calculated, these studies neglect dosimetric perturbations arising from the contralateral colpostat or the intrauterine tandem. Dosimetric effects of inhomogeneities in brachytherapy is essential for both dose‐based implant optimization as well as for a comparison with alternate modalities, such as intensity modulated radiation therapy. We have used Monte Carlo calculations to model dose distributions about both a Fletcher–Suit–Delclos (FSD) low dose‐rate system and the microSelectron high dose‐rate remote afterloading system. We have evaluated errors, relative to a Monte Carlo simulation based upon a complete applicator system, in superposition calculations based upon both precalculated single shielded applicator dose distributions as well as single unshielded source dose distributions. Errors were largely dominated by the primary photon attenuation, and were largest behind the shields and tandem. For the FSD applicators, applicator superposition showed differences ranging from a mean of 2.6% at high doses (>Manchester Point A dose) to 4.3% at low doses (