王金媛; 曲宝林; 徐寿平; 潘隆盛; 鞠忠建; 杨涛; 徐伟

doi:10.3760/cma.j.issn.1004-4221.2017.11.011

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• 物理·生物·技术 •

CyberKnife固定与可变准直器颅内SRT计划质量及执行效率应用评价

中华放射肿瘤学杂志, 2017,26(11) : 1292-1297. DOI: 10.3760/cma.j.issn.1004-4221.2017.11.011

摘要

目的

探讨与评价运用第5代CyberKnife VSI系统中固定(Fixed)和可变(Iris)准直器实施颅内肿瘤SRT时计划质量的剂量学特性。

方法

选择20例颅内肿瘤患者分为A、B两组，A、B组分别为小、大体积靶区组，每组10例，统一靶区剂量21 Gy分3次。分别对每例患者选择Fixed和Iris准直器进行治疗计划设计。通过靶区CI、HI、GI、GSI与OAR等剂量学参数，分析评估SRT计划优化质量及实施效率，从而评价两套准直器的束流特性情况。采用配对t检验分析其差异。

结果

Iris计划执行的平均时间明显优于Fixed计划(A组P＝0.001；B组P＝0.000)。B组中低剂量区(20%、10%处方剂量)体积Fixed计划明显低于Iris计划(P＝0.001、0.009)。对于OAR，B组中视通路Dmin及眼球Dmean、Dmin具有统计学差异(P均<0.05)，A组中仅视交叉Dmin具有统计学意义(P＝0.043)。对于靶区相关参数两组均相近(P均>0.05)。

结论

利用第5代CyberKnife VSI系统治疗颅内小体积肿瘤时，Iris与Fixed准直器相比，除治疗时间明显缩短外无明显剂量学特性差异。对体积较大且形状复杂的肿瘤靶区，Iris计划虽然正常器官限量在允许范围内，但其低剂量区体积要明显略高于Fixed计划。而对于两种准直器更深层次剂量学特性，仍需更多病例进一步研究可能。

引用本文: 王金媛, 曲宝林, 徐寿平, 等. CyberKnife固定与可变准直器颅内SRT计划质量及执行效率应用评价 [J] . 中华放射肿瘤学杂志, 2017, 26(11) : 1292-1297. DOI: 10.3760/cma.j.issn.1004-4221.2017.11.011.

参考文献导出: Endnote NoteExpress RefWorks NoteFirst 医学文献王

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SRT已成为颅内肿瘤临床治疗的重要手段之一。实施SRT的各种设备和技术方法需满足例如动静脉畸形^[1,2,3,4]、脑膜瘤^[5]、听神经瘤^[4,6]、脑转移瘤^[7]、三叉神经鞘瘤^[8]等不同类别颅内肿瘤的临床治疗要求。这些设备和方法均具有其各自的特色和优势，而CyberKnife系统因其精确性及高度临床可接受度，俨然已成为神经外科和放疗的新利器，有力地推动了SRT技术发展。CyberKnife实施SRT优势之一在于其准直器的特殊设计及组合方式。第5代CyberKnife VSI系统可配有固定(Fixed)和可变(Iris™)两套准直器，其物理结构存在一定差别。Iris准直器利用钨块系列形成一套12边形可变形状，从而在单个治疗路径中可任意变换准直器的尺寸进行组合，迅速改变射束几何大小即实现自动更换准直器。而Fixed准直器由12个固定大小准直器组成，治疗过程中若需要改变射野大小，则需人为进入治疗室更换准直器或治疗机头从治疗位置移动到准直器台实施更换。因此，与Fixed准直器相比，Iris准直器能有效减少更换时间，从而缩短治疗时间，提高舒适度^[9]。为进一步探讨两套不同准直器物理结构的特点，本研究拟探究并评价运用第5代CyberKnife VSI系统中两套不同准直器实施颅内肿瘤SRT时计划质量、效率及剂量学特性差异，从而为临床实施提供一定参考依据。

贡献者信息

王金媛

100853　北京，解放军总医院放疗科

曲宝林

100853　北京，解放军总医院放疗科

徐寿平

100853　北京，解放军总医院放疗科

潘隆盛

100853　北京，解放军总医院神经外科

鞠忠建

100853　北京，解放军总医院放疗科

杨涛

100853　北京，解放军总医院放疗科

徐伟

100853　北京，解放军总医院放疗科

通信作者

徐寿平

100853　北京，解放军总医院放疗科

Email：shouping_xu@yahoo.com

关键词

射波刀; 准直器; 计划质量; 剂量学;

基金项目

国家自然科学基金课题（11275105）

历史

出版日期：2017-11-15

收稿日期：2016-10-10

Physics·Biology·Technique

Evaluation of the quality and efficiency of SRT plans for intracranial tumors using Fixed and Iris collimators of CyberKnife

Jinyuan Wang, Baolin Qu, Shouping Xu, Longsheng Pan, Zhongjian Ju, Tao Yang, Wei Xu

Published 2017-11-15

Cite as Chin J Radiat Oncol, 2017, 26(11): 1292-1297. DOI: 10.3760/cma.j.issn.1004-4221.2017.11.011

Abstract

Objective

To discuss and evaluate the dosimetric characteristics of different plans implementing stereotactic radiotherapy (SRT) for intracranial tumors using Fixed and Iris collimators of CyberKnife VSI.

Methods

Twenty patients with intracranial tumors were selected and divided into group A with a small target volume (≤30 cm³) and group B with a large target volume (≥30 cm³). There were 10 patients in each group, and the prescribed dose to the target was 21 Gy in 3 fractions. For each patient, two treatment plans were designed using Fixed and Iris collimators. By analyzing the dosimetric parameters such as conformity index (CI), homogeneity index (HI), gradient index (GI), gradient score index (GSI), and organs at risk (OAR), the quality and efficiency of the plans were evaluated in order to discuss the beam characteristics for two sets of collimators. The difference was analyzed with the paired t-test.

Results

The mean time of Iris plan for delivering was significantly less than that of Fixed plan (group A: P=0.001; group B: P=0.000). In group B, the peripheral dose (20% and 10% of the prescribed dose) volumes of Fixed plan were significantly less than those of Iris plan (P=0.001 and 0.009). For OAR, Dmin of the visual pathway and Dmean or Dmin of the eyeball in group B were significantly different between Fixed and Iris plans (all P<0.05), while in group A, only Dmin of the optic chiasm was significantly different between the two plans (P=0.043). For the other parameters of targets, there were no significant differences between Fixed and Iris plans in both groups (all P>0.05).

Conclusions

Apart from less treatment time in the Iris plan, there are no significant dosimetric differences between the two collimator plans of CyberKnife VSI in treating small intracranial tumor. For the large and complex tumor, although Iris plan meets the requirement for OAR dose constraints, its low-dose volumes are larger than those of Fixed plan. Further studies of the dosimetric characteristics in CyberKnife should be done.

Key words:

CyberKnife; Collimator; Plan quality; Dosimetric characteristics

Contributor Information

Jinyuan Wang