El-Bassiouni Mazen, Davis J Bernard, El-Attar Inas, Studer Gabriela M, Lütolf Urs M, Ciernik I Frank
Radiation Oncology, Zurich University Hospital, University of Zurich, Zurich, Switzerland.
Strahlenther Onkol. 2006 Sep;182(9):531-6. doi: 10.1007/s00066-006-1581-1.
To prospectively define the setup error and the interfraction prostate localization accuracy of the planning target volume (PTV) in the presence of an endorectal balloon (ERB) device.
Weekly portal images (PIs) of 15 patients undergoing external-beam radiotherapy were analyzed. Displacements of the isocenter and the center of the ERB were measured. The setup and target motion variability were assessed with regard to the position variability of the ERB.
The setup error was random and target motion variability was largest in the craniocaudal direction. The mean displacement of the isocenter was 2.1 mm (+/-1.2 mm SD [standard deviation]), 2.4 mm (+/-2.2 mm SD), and 3.8 mm (+/-4.0 mm SD) in the left-right, craniocaudal, and anteroposterior directions, respectively (p=0.1). The mean displacement of the ERB was 2.0 mm (+/-1.4 mm SD), 4.1 mm (+/-2.0 mm SD), and 3.8 mm (+/-3.3 mm SD; p=0.03). Setup margin and internal margin contributed equally to the PTV margin. Cumulative placement insecurity of the field and the ERB together was 4.0 mm (+/-2.1 mm SD) laterally, 6.4 mm (+/-2.5 mm SD) craniocaudally, and 7.7 mm (+/-7.0 mm SD) anteroposteriorly. The 95% CIs (confidence intervals) were 2.9-5.2 mm, 5.1-7.8 mm, and 3.8-11.5 mm. In 35% of cases, the estimation of the dorsal margin exceeded 1 cm.
Margin estimate dorsally may exceed 1 cm and on-line position verification with an ERB cannot be recommended for dose escalation>70 Gy.
前瞻性地确定在使用直肠内气囊（ERB）装置的情况下，计划靶区（PTV）的摆位误差和分次间前列腺定位准确性。
分析了15例接受外照射放疗患者的每周射野图像（PI）。测量了等中心和ERB中心的位移。根据ERB的位置变异性评估摆位和靶区运动变异性。
摆位误差是随机的，靶区运动变异性在头脚方向上最大。等中心在左右、头脚和前后方向上的平均位移分别为2.1 mm（±1.2 mm标准差[SD]）、2.4 mm（±2.2 mm SD）和3.8 mm（±4.0 mm SD）（p = 0.1）。ERB的平均位移分别为2.0 mm（±1.4 mm SD）、4.1 mm（±2.0 mm SD）和3.8 mm（±3.3 mm SD；p = 0.03）。摆位边界和内部边界对PTV边界的贡献相等。射野和ERB总的累积放置不安全性在横向为4.0 mm（±2.1 mm SD），在头脚方向为6.4 mm（±2.5 mm SD），在前后方向为7.7 mm（±7.0 mm SD）。95%置信区间（CI）为2.9 - 5.2 mm, 5.1 - 7.8 mm和3.8 - 11.5 mm。在35%的病例中，背侧边界的估计超过1 cm。
背侧边界估计可能超过1 cm，不推荐使用ERB进行在线位置验证以进行剂量递增>70 Gy。
