Lausanne University Hospital (CHUV), Department of Clinical Neurosciences, Neurosurgery Service and Gamma Knife Center, Switzerland.
Lausanne University Hospital (CHUV), Department of Clinical Neurosciences, Neurosurgery Service and Gamma Knife Center, Switzerland; University of Lausanne (UNIL), Faculty of Biology and Medicine (FBM), Switzerland.
Phys Med. 2024 Oct;126:104820. doi: 10.1016/j.ejmp.2024.104820. Epub 2024 Sep 27.
Recent studies suggest strong correlations between Biologically Effective Doses (BED) and single fraction stereotactic radiosurgery treatment outcomes, as demonstrated for vestibular schwannomas (VS), arterio-venous malformations and pituitary adenomas. The BEDs calculated in these studies consider an uniform dose delivery where the spatio-temporal aspects of dose delivery were neglected.
The aim of the study is to quantify the discrepancies between the BED values calculated with a simplified model of uniform dose delivery against the more complex model that incorporates the temporo-spatial incrementation of dose delivery and the bi-exponential effect of the sub-lethal damage repair.
A software tool that computes the BED distributions based on individual isocenter dose matrices extracted from the GammaPlan (Elekta) treatment planning was developed. Two cohorts 5 VS and 5 jugular foramen schwannoma cases of various tumor volumes and isocenter number were utilized to benchmark the method. Their BEDs covering 98% of tumor volumes were compared against those determined with the uniform delivery model.
The BEDs covering 98% of the tumor volumes as calculated with both models show an approximately linear dependency with the treatment time. For all studied cases, the uniform delivery model overestimates the BEDs calculated with the full spatio-temporal delivery model. This discrepancy seems to accentuate with the tumor volume and treatment complexity.
Despite their resemblance, the BED distributions provide a plethora of BED measures more suitable to characterize clinical outcomes than the unique peripheral BED value calculated with the simplified model of uniform dose delivery.
最近的研究表明，生物有效剂量（BED）与单次立体定向放射外科治疗结果之间存在很强的相关性，这已在前庭神经鞘瘤（VS）、动静脉畸形和垂体腺瘤中得到证实。这些研究中计算的 BED 考虑了均匀剂量分布，而忽略了剂量分布的时空方面。
本研究的目的是量化在均匀剂量分布简化模型中计算的 BED 值与更复杂的模型之间的差异，该模型纳入了剂量分布的时空递增和亚致死损伤修复的双指数效应。
开发了一种软件工具，该工具基于从 GammaPlan（Elekta）治疗计划中提取的各个等中心点剂量矩阵来计算 BED 分布。利用两个队列，即 5 例 VS 和 5 例颈静脉孔神经鞘瘤病例，这些病例的肿瘤体积和等中心点数量各不相同，用于基准测试该方法。比较了覆盖 98%肿瘤体积的两种模型的 BED 值。
两种模型计算的覆盖 98%肿瘤体积的 BED 值与治疗时间大致呈线性关系。对于所有研究病例，均匀剂量分布模型高估了使用完整时空剂量分布模型计算的 BED 值。这种差异似乎随着肿瘤体积和治疗复杂性的增加而加剧。
尽管相似，BED 分布提供了大量的 BED 指标，比使用均匀剂量分布简化模型计算的独特外周 BED 值更适合于描述临床结果。
