ArcCheck对Tomotherapy叶片打开时间误差检测的灵敏度研究  

Sensitivity evaluation of ArcCheck in detecting leaf open time errors of helical tomotherapy delivery

作　　者：岳麒[1] 段继梅[1] 肖斌[2] 王志伟[1] 张岳 杨秀美[1] 谷丹[1] Yue Qi;Duan Jimei;Xiao Bin;Wang Zhiwei;Zhang Yue;Yang Xiumei;Gu Dan(Department oj Radiation Oncology,First Affiliated Hospital of Kunming Medical University,Kunming 650032,China;School of Materials and Energy,Yunnan University,Kunming 650032,China)

机构地区：[1]昆明医科大学第一附属医院肿瘤放疗科,650032 [2]云南大学材料与能源学院,昆明650032

出　　处：《中华放射肿瘤学杂志》2021年第5期492-497,共6页Chinese Journal of Radiation Oncology

摘　　要：目的通过对螺旋断层治疗(简称Tomo)计划人为引入叶片打开时间误差进行测试,评估中心型及偏心型两种ArcCheck验证方式在Tomo治疗计划质量验证中对叶片打开时间误差的灵敏度。方法选择9例鼻咽癌患者,每个患者均分别生成靶区置于ArcCheck周围探测器上的偏心型验证计划、靶区置于ArcCheck中心位置的中心型验证计划。通过Matlab修改Sinogram矩阵文件人为引入2、4、6、8、10 ms的延时打开时间误差。利用ArcCheck分别测试无误差计划及带误差计划,对验证结果进行γ分析(剂量距离误差标准分别为3%/3 mm、3%/2 mm、2%/2 mm,阈值水平分别选择5%、10%、15%)。对误差灵敏度分别利用γ下降梯度和最小误差检测能力进行定量评估。对不同剂量距离误差标准及不同阈值水平分析结果的γ通过率进行Pearson法相关性分析。结果中心型计划的γ下降梯度绝对值在不同γ分析标准下均大于偏心型计划(均P<0.05)。中心型计划在所有γ分析标准下能检测出的最小叶片打开时间误差均为2 ms,而偏心型计划的最小误差检测能力弱于偏心型计划。中心型验证计划3个剂量距离误差标准的γ通过率均为强相关(均R2>0.9),而偏心型计划仅3%/3 mm、3%/2 mm标准的相关性较强(R2>0.9)。偏心型及中心型验证计划不同阈值水平间的γ通过率相关性均为强相关(R2均接近1)。结论ArcCheck应用于Tomo验证的中心型验证方式比偏心型验证方式对叶片打开时间误差灵敏度更高,对误差的检测能力中心型计划强于偏心型计划,且中心型验证计划在不同标准下的γ分析结果的相关性均强于偏心型验证计划。建议Tomo临床计划验证采用ArcCheck中心型验证方式。Objective To evaluate the sensitivity of the ArcCheck dosimetry system in detecting the leaf open time errors during the center and off-center helical tomotheray delivery quality assurance(DQA).Methods Nine nasopharyngeal carcinoma(NPC)patients were selected in this study.Two DQA plans were created for each patient:the"center"plan was created by moving the image of the ArcCheck phantom to place the high dose region on the phantom center and the"off-center"plan was created by offsetting the phantom and putting several diodes through a higher does region.Leaf open time errors of 2,4,6,8 and 10 ms were introduced to the Sinogram which was modified using Matlab.Each intentional error plan and original(no error)plan for each patient were measured using both"center"and"off-center"DQA methods,theγanalysis was performed to evaluate the DQA results.The different dose and distance error criteria of 3%/3 mm,3%/2 mm and 2%/2 mm were selected,and different thresholds of 5%,10%and 15%were selected forγanalysis.The gradient and the minimum detectable error approach were taken to quantitatively analyze the sensitivity.The correlation between different dose distance error criteria and different thresholds was also evaluated by Pearson correlation analysis.Results The absolute value ofγgradient of the"center"DQA plans were larger than those of the"off-center"plans in all differentγcriteria(all P<0.05).The stricter theγcriteria were adopted,the more sensitive DQA results of leaf open time error were obtained.The minimum detectable error was 2 ms in all differentγcriteria for the"center"DQA plan.The minimum error detectability of the"off-center"DQA plan was weaker than that of the"center"DQA plan.Theγpassing rates of three different dose distance error criteria were significantly strongly correlated for the"center"DQA plan(R2>0.9).For the"off-center"DQA plan,only the 3%/3 mm and 3%/2 mm criteria were significantly strongly correlated(R2>0.9).Significant strong correlation was observed in theγpassing rate at different thresho

关 键 词：螺旋断层治疗 质量保证 γ通过率 灵敏度分析 

分 类 号：R730.55[医药卫生—肿瘤]