ABSTRACT

Purpose: The dosimetric characteristics between four-dimensional with end-expiration and end-inspiration CT dose distributions of Cyberknifeare to be evaluated.

Methods: A set of four dimensional (4D) CT images and two sets of CT scans,includingend-inspiration and end-expiration breath-hold, were obtained from 15 CyberKnife treated patients. Three internal target volumes (ITVs) were created from the three sequence images. Allpatients were treated using ITV-based strategy with an additional ITV-to-PTV margin of 3 mm.

Results: In all of the 15 patients, the PTVfuse consistently has the smallest volumes compared to other PTV’s. The nCI and coveragesof the plans were based on PTVfuse, which provided statistically significant differences for PTV4DE and PTV4DI. Additionally, the dose of normal tissue showed no statistical differences in the three type of plans (plan PTV4DE VS PTV4DI, p = 0.76), (plan PTV4DE VSPTVfuse, p = 0.23) and (plan PTV4DI VSPTVfuse, p = 0.16).

Conclusion: The fusion of breath-hold sequences is beneficial to provide excellent target coverage than the end-inspiration or end-expiration with 4D-CT approach for target definition. Furthermore, the fusion of the end-expiration and end-inspiration CT scans may be used as an alternative to 4D CT in the absence of multi-modality images.

摘要

目的：评价射波刀四维呼气末和吸气末CT剂量分布的剂量学特征。

方法：从 15 名射波刀治疗的患者中获得一组四维 (4D) CT 图像和两组 CT 扫描，包括吸气末和呼气末屏气。从三个序列图像创建了三个内部目标体积 (ITV)。所有患者均使用基于 ITV 的策略进行治疗，额外的 ITV 到 PTV 边缘为 3 毫米。

结果：在所有 15 名患者中，与其他 PTV 相比，PTVfuse 始终具有最小的体积。计划的 nCI 和覆盖范围基于 PTVfuse，它为 PTV4DE 和 PTV4DI 提供了统计学上的显着差异。此外，正常组织的剂量在三种类型的计划（计划 PTV4DE VS PTV4DI，p = 0.76）、（计划 PTV4DE VSPTVfuse，p = 0.23）和（计划 PTV4DI VSPTVfuse，p = 0.16）中没有显示出统计学差异。

结论：与吸气末或呼气末的 4D-CT 方法相比，屏气序列的融合有利于提供出色的目标覆盖范围。此外，在没有多模态图像的情况下，呼气末和吸气末 CT 扫描的融合可用作 4D CT 的替代方案。