伽玛刀治疗计划的优化问题研究

The optimization of treatment planning in Gamma knife radiosurgery

目的探讨伽玛刀治疗计划的优化问题。方法回顾性分析2005年2月～2006年9月,386例病人的治疗计划,按照所使用准直器的规格,分为1～3种准直器组合(以下分别简称1种组、2种组、3种组)。根据剂量-容积直方图提供的参数计算病灶覆盖率(TC)、适形指数(CI)及平均剂量并加以比较。结果使用多准直器组合(2种组和3种组)较使用单一准直器,能获得较高的TC(P<0.01)和较理想的CI(P<0.05),其差别具有统计学意义。1种组在平均剂量上明显高于其他组(P<0.01)。2种组与3种组在上述指标上的差别无统计学意义(P>0.05)。结论在设计治疗计划时,采用多等中心、多准直器联合可有效地提高病灶的覆盖率和适形性,但同时过多等中心又会造成病灶内部的剂量不均匀,因此我们提倡通过大小不同的准直器组合使用、合理布局来优化剂量计划。

Objective To evaluate the optimization of Gamma knife treatment planning. Methods The treatment planning was retrospectively reviewed in 386 patients treated by Gamma knife radiosurgery from Feb. 2005 to Sep. 2006. The dose plans were divided into three groups according to the size of the collimators used in the treatment plans： single-size-collimator plan, two-size-collimator plan, and three-size-collimator plan. Each plan was analyzed using dose-volume histogram in conjunction with the target coverage, conformity index and mean target dose. Results Multi-size-collimator plans achieved improved target coverage values （P〈0.01） and conformity indices （P〈0.05） as compared with the single-size-collimator plans The mean target dose values in single size-collimator plans were significantly higher （P〈0.01）. Two-size-collimator plans showed no significant differences in the coverage values, conformity indices and mean target dose values compared with three-size- collimator plans （P〉0.05）. Conclusion It is possible to achieve highly target volume coverage and conformal dose distribution using multiple isocenters and different size collimators in Gamma knife radiosurgery, but excessive isocenters could lead to dose heterogeneity within the target. Therefore, combination of different-size collimators and appropriate isocenter parameters should be associated with the optimization of Gamma Knife treatment planning.