摘要目的 分析调强放疗计划面剂量验证过程中剂量计算的分辨率对Gamma通过率结果的影响,找出针对不同评判标准对应恰当的计算分辨率数值.方法 选取25例调强放疗计划进行面剂量验证,对比分析采用2 mm计算分辨率时,使用3 mm/3％、2 mm/2％和1 mm/1％不同评判标准的Gamma通过率结果.采用0.5、1、3、4、5 mm不同的分辨率计算并输出面剂量分布,分别与使用Mapcheck测量到的该平面剂量分布进行Gamma通过率分析,对比分析采用不同计算分辨率得到的面剂量验证Gamma通过率结果.结果 25例计划的225个射野的面剂量验证Gamma通过率均值随着计算分辨率的增大而降低.采用3 mm/3％的评判标准时,计算分辨率为1 mm的面剂量验证Gamma通过率为98.3％±1.3％,与分辨率为0.5 mm的通过率98.3％±1.2％的数值很接近,其差异无统计学意义(P＞0.05).计算分辨率≥3 mm的面剂量验证Gamma通过率相比于计算分辨率为0.5 mm的通过率均显著降低,其差异具有统计学意义(P＜0.05).采用2 mm/2％的评判标准时,计算分辨率≥1 mm的面剂量验证Gamma通过率与计算分辨率为0.5 nn的通过率相比均有显著下降,其差异具有统计学意义(P＜0.05).结论 面剂量分布的计算分辨率的增大会导致面剂量验证Gamma通过率的下降,应采用数值较低的分辨率计算面剂量分布,以消除计算分辨率对Gamma通过率结果的影响.建议采用3 mm/3％评判标准时剂量计算的分辨率选择1 mm,采用2 mm/2％的评判标准时剂量计算的分辨率选择0.5 mm,以保证验证结果的可靠性.

abstractsObjective To analyze the impact of dose calculation resolution on Gamma pass rate for planar dose distribution verification of intensity-modulated radiotherapy (IMRT),and to find out the appropriate calculation resolution value with specific applied criteria.Methods 25 IMRT plans were selected for the planar dose verification.The Gamma pass rates with 3 mm/3％,2 mm/2％ and 1 mm/1％ criteria were compared and analyzed.The planar dose distributions were calculatedand exported from TPS with different resolutions of 0.5,1,2,3,4 and 5 mm.The pass rates of Gamma analysis between the computed dose distributions with different resolutions and the dose distributions measured by Mapcheck device were compared and analyzed.Results The average Gamma pass rates of all the 225 fields decreased with the increment of calculation resolution.When the pass rates of Gamma analysis were calculated using 3 mm/3％ criteria,the gamma pass rate with 1 mm and 0.5 mm calculation resolution were (98.3±1.3)％ and (98.3±1.2)％,respectively.The results were almost the same and the difference wasn't statistically significant (P＞0.05).The gamma pass rates with greater than or equal to3 mm calculation resolution were significantly less than the pass rate with 0.5 mm calculation resolution (P＜0.05).When the pass rates of Gamma analysis were calculated using 2 mm/2％ criteria,all the pass rates with greater than 0.5 mm calculation resolution were significantly less than the pass rate with 0.5 mm calculation resolution (P＜0.05).Conclusions The Gamma pass rates of planar dose verification reduce significantly with the increment of calculation resolution.In order to reduce the effect of calculation resolution on Gamma pass rate,the lower calculation resolution should be used.When using the 3 mm/3％ criteria for the Gamma analysis,1 mm calculation resolution is recommended.When using the 2 mn/2％ criteria for the Gamma analysis,0.5 mm calculation resolution is recommended.The appropriate calculation resolution will ensure the reliability of planar dose verification.