SU-D-211-03：一种使用伽玛刀Perfexion进行单次分割和分次立体定向放射治疗的自动逆向计划优化方法。

SU-D-211-03: An Automated Inverse Planning Optimization Approach for Single- Fraction and Fractionated Radiosurgery Using Gamma Knife Perfexion.

作者信息

Ghobadi K, Ghaffari H, Aleman D, Ruschin M, Jaffray D

机构信息

University of Toronto, Toronto, Ontario, Canada.

Odette Cancer Centre, Toronto, Canada.

出版信息

Med Phys. 2012 Jun;39(6Part3):3610. doi: 10.1118/1.4734657.

DOI:10.1118/1.4734657

PMID:28517428

Abstract

PURPOSE

The purpose of this work is to develop an automated inverse planning approach to generate singe-fraction and fractionated stereotactic radiosurgery (SRS) treatment plans for Gamma Knife Perfexion.

METHODS

Our automated approach consists of two steps: 1) a grassfire-based algorithm to carefully determine the isocentre locations; 2) a penalty-based optimization to find the optimal shot shapes and their intensities to minimize the deviation of the delivered dose from the objective dose in all structures. For single-fraction SRS, a margin-less approach was taken: conformity of dose to the gross tumor volume (GTV) with a steep dose fall-off was prioritized. For fractionated radiosurgery, dose homogeneity was given a higher priority since planning target volumes (PTV) were applied to account for daily setup variation, and these PTVs could overlap with organs-at-risk (OARs). The two-step approach was tested on seven clinical cases with PTV sizes of 0.5cm̂3-56.5cm̂3. In the tested cases, the PTV had 0%-38% overlap with OARs.

RESULTS

For single-fraction SRS, the dose to 1mm̂3 brainstem was on average 0.24Gy (range: -2.4Gy to +2.0Gy) lower compared to manually-generated plans. Beam-on time varied with the number of isocentres, but on average was 33min longer than manually- generated plans. The optimization algorithm took 215min on average, while isocentre selection performed in <10s.For fractionated SRS, the average PTV coverage was V95=94.9% (range: 92.7%-97.6%) and the mean dose to 1 mm̂3 brainstem was 87.8% of the prescription dose (range: 35.4%- 108.8%). The mean beam-on time per fraction per dose-per-fraction was 4.8min/Gy (range: 0.9min/Gy-10.3min/Gy). We observed a tradeoff between conformity and OARs-sparing in both plans, and added sensitivity to isocentre locations in fractionated plans. In all the cases, GTV received the full prescription dose.

CONCLUSIONS

The results indicated that automated inverse planning yields improved conformity and OAR-sparing for single- fraction SRS and is capable of generating homogeneous fractionated SRS. This work is partially funded by Elekta Instrument, AB, Stockholm, Sweden.

摘要

目的

本研究旨在开发一种自动逆向计划方法，用于为伽玛刀Perfexion生成单次分割和分次立体定向放射外科（SRS）治疗计划。

方法

我们的自动方法包括两个步骤：1）基于草火算法仔细确定等中心位置；2）基于惩罚的优化，以找到最佳射野形状及其强度，以最小化所有结构中实际剂量与目标剂量的偏差。对于单次分割SRS，采用了无边缘方法：优先考虑剂量与大体肿瘤体积（GTV）的一致性以及陡峭的剂量下降。对于分次放射外科，剂量均匀性被赋予更高的优先级，因为应用计划靶体积（PTV）来考虑每日设置变化，并且这些PTV可能与危及器官（OAR）重叠。在7例PTV大小为0.5cm³ - 56.5cm³的临床病例上测试了这种两步法。在测试病例中，PTV与OAR的重叠率为0% - 38%。

结果

对于单次分割SRS，与手动生成的计划相比，1mm³脑干的平均剂量低0.24Gy（范围：-2.4Gy至+2.0Gy）。照射时间随等中心数量而变化，但平均比手动生成的计划长33分钟。优化算法平均耗时215分钟，而等中心选择在不到10秒内完成。对于分次SRS，平均PTV覆盖率为V95 = 94.9%（范围：92.7% - 97.6%），1mm³脑干的平均剂量为处方剂量的87.8%（范围：35.4% - 108.8%）。每次分次每Gy剂量的平均照射时间为4.8分钟/Gy（范围：0.9分钟/Gy - 10.3分钟/Gy）。我们在两个计划中都观察到了适形性和保护OAR之间的权衡，并且在分次计划中等中心位置的敏感性增加。在所有病例中，GTV接受了全部处方剂量。