This study evaluated unexpected dosimetric errors caused by machine control accuracy, patient setup errors, and patient weight changes/internal organ deformations. Trajectory log files for 13 gynecologic plans with seven‐ or nine‐beam dynamic multileaf collimator (MLC) intensity‐modulated radiation therapy (IMRT), and differences between expected and actual MLC positions and MUs were evaluated. Effects of patient setup errors on dosimetry were estimated by in‐house software. To simulate residual patient setup errors after image‐guided patient repositioning, planned dose distributions were recalculated (blurred dose) after the positions were randomly moved in three dimensions 0–2 mm (translation) and 0°–2° (rotation) 28 times per patient. Differences between planned and blurred doses in the clinical target volume (CTV) D_98% and D_2% were evaluated. Daily delivered doses were calculated from cone‐beam computed tomography by the Hounsfield unit‐to‐density conversion method. Fractional and accumulated dose differences between original plans and actual delivery were evaluated by CTV D_98% and D_2%. The significance of accumulated doses was tested by the paired t test. Trajectory log file analysis showed that MLC positional errors were −0.01 ± 0.02 mm and MU delivery errors were 0.10 ± 0.10 MU. Differences in CTV D_98% and D_2% were <0.5% for simulated patient setup errors. Differences in CTV D_98% and D_2% were 2.4% or less between the fractional planned and delivered doses, but were 1.7% or less for the accumulated dose. Dosimetric errors were primarily caused by patient weight changes and internal organ deformation in gynecologic radiation therapy.

中文翻译：

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轨迹记录分析和基于锥束CT的每日剂量计算，以研究妇科癌症调强放射疗法的剂量学准确性

这项研究评估了由机器控制精度，患者设置错误以及患者体重变化/内部器官变形引起的意外剂量错误。使用七束或九束动态多叶准直仪（MLC）强度调制放射治疗（IMRT）评估了13项妇科计划的轨迹日志文件，并评估了预期和实际MLC位置和MU之间的差异。通过内部软件评估了患者设置错误对剂量测定的影响。为了模拟以图像为导向的患者重新定位后的残留患者设置错误，在每个位置随机移动三个位置0–2 mm（平移）和0°–2°（旋转）三个维度后，重新计算计划的剂量分布（模糊剂量）病人。临床目标量（CTV）中计划剂量和模糊剂量之间的差异D _98％评估D _2％。通过Hounsfield单位密度转换法根据锥束计算机断层扫描计算出每日给药剂量。CTV D _98％和D _2％评估了原始计划和实际分娩之间的分数和累积剂量差异。累积剂量的显着性通过配对t检验进行了检验。轨迹日志文件分析显示，MLC位置误差为-0.01±0.02 mm，MU传递误差为0.10±0.10 MU。对于模拟患者设置错误，CTV D _98％和D _2％的差异<0.5％。CTV D _98％和D _2％的差异计划剂量和分次给药剂量之间的差异为2.4％或更低，但累积剂量为1.7％或更低。剂量学误差主要由妇科放射治疗中患者体重变化和内部器官变形引起。