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目的:通过在Mapcheck分析软件中挪动调强放疗验证计划计算剂量分布图中心位置的方法,研究Mapcheck半导体矩阵板摆位误差对调强放疗验证计划通过率的影响。方法:收集2014年8月至2015年2月某科室调强放疗验证计划36例,验证计划采用的Gamma通过率标准为3%/3 mm。首先记录调强放疗验证计划计算的剂量分布图中心位置不变时的Gamma通过率γ_0,然后测量将该计划计算的剂量分布图中心位置在x、y轴向上分别移动-5、-2、-1、1、2、5 mm时的Gamma通过率;最后测量将该计划计算的剂量分布图绕中心点顺时针方向转动-5、-2、-1、1、2和5°时的Gamma通过率。对以上Gamma通过率取平均值比较并做统计分析。结果:γ_0为(97.44±2.59)%;计算的剂量分布图中心位置在x、y轴移动-5、-2、-1、1、2、5 mm时,x方向的Gamma通过率分别为(63.91±7.51)%、(93.02±4.66)%、(97.01±2.83)%、(96.83±2.60)%、(92.54±4.02)%和(63.23±7.81)%,y方向的Gamma通过率分别为(68.55±8.28)%、(89.68±5.51)%、(95.20±3.82)%、(97.42±2.55)%、(94.42±4.01)%和(73.61±9.07)%;计算的剂量分布图绕中心点顺时针方向转动-5、-2、-1、1、2和5°时,Gamma通过率分别为(76.58±8.31)%、(93.42±4.90)%、(96.42±3.44)%、(96.38±2.71)%、(93.90±3.31)%和(78.74±6.94)%。所有数据与γ_0比较都具有统计学差异(P<0.01)。结论:Mapcheck半导体矩阵板的摆位影响了Gamma通过率,且在不同方向上对Gamma通过率的影响存在差别。当摆位误差超过2 mm或者2°时,可以使Gamma通过率下降约5%,应当引起验证人员对Mapcheck摆位工作的重视。
OBJECTIVE: To study the influence of setup errors of Mapcheck semiconductor matrix on the pass-through rate of intensity-modulated radiotherapy (IMRT) validation program by calculating the center of the dose distribution map by using Maprtck analysis software. Methods: Totally 36 cases of intensity modulated radiotherapy in one department were collected from August 2014 to February 2015. The Gamma passing rate of validation scheme was 3% / 3 mm. First, record the Gamma pass rate γ_0 when the center of the dose distribution map calculated by the intensity-modulated radiotherapy validation plan is calculated, and then move the center of the dose distribution map calculated by the plan in the x and y axes respectively by -5 and -2, -1, 1, 2, 5 mm; finally measuring the dose distribution calculated by the program around the center point clockwise -5, -2, -1, 1, 2 and 5 ° Gamma Passing rate. Compare the above Gamma pass rates and do statistical analysis. Results: γ_0 was (97.44 ± 2.59)%. When the center of the calculated dose distribution was shifted by -5, -2, -1, 1, 2 and 5 mm in x and y axes, the Gamma passing rates in x direction were ( 63.91 ± 7.51%, (93.02 ± 4.66)%, (97.01 ± 2.83)%, (96.83 ± 2.60)%, (92.54 ± 4.02)% and (63.23 ± 7.81)%, respectively. 68.55 ± 8.28)%, (89.68 ± 5.51)%, (95.20 ± 3.82)%, (97.42 ± 2.55)%, (94.42 ± 4.01)% and (73.61 ± 9.07)%, respectively. The passing rates of Gamma were (76.58 ± 8.31)%, (93.42 ± 4.90)%, (96.42 ± 3.44)%, (96.38 ± 2.71)% respectively in the clockwise direction of -5, -2, -1, )%, (93.90 ± 3.31)% and (78.74 ± 6.94)%, respectively. All data were statistically different from γ_0 (P <0.01). Conclusion: The placement of Mapcheck semiconductor matrix boards affects the Gamma pass rate, and there are differences in the Gamma pass rates in different directions. Gamma throughput rates can be reduced by about 5% when setup errors exceed 2 mm or 2 °, and should warrant testers’ attention to the Mapcheck setup.