Miralbell Raymond, Caro Monica, Weber Damien C, Elizalde Javier, Perez-Ochoa Agata, Villà Salvador, IgnacioToscas José, Martinez Pedro, Linero Dolors, Nouet Philippe, Escudé Lluís
Instituto Oncologico Teknon, Barcelona, Spain.
Technol Cancer Res Treat. 2007 Oct;6(5):413-7. doi: 10.1177/153303460700600506.
To assess the reliability and target positioning reproducibility with eyes closed in uveal melanoma patients treated with a micromultileaf-based linear accelerator dedicated for stereotactic radiotherapy. Five consecutive patients treated with curative radiotherapy for uveal melanoma were monitored for positioning reproducibility with resimulation CT scans performed every two days while on treatment (23 resimulation CTs available). All patients underwent MRIs of the orbits before simulation to help to define the target and organs at risk (e.g., lenses, optic nerves, ciliary bodies, and lacrimal glands) in the simulation CT (MRI-to-CT bone registration). Patients were simulated, resimulated, and treated with eyes closed. Patient #1 was treated with 5 daily fractions while patients #2 to #5, were treated with 10 daily fractions. We chose the lens of the tumor-bearing eye as the structure to be controlled, assuming that correct repositioning of the lens should be a valid surrogate for correctness of target repositioning. Displacements (mean and standard deviations, SD) of the lens in the three axes were measured for each patient. Systematic and standard errors were calculated. Planning target volume (PTV) margins were estimated according to McKenzie et al. [Phys Med Biol 45, 3331-3342 (2000)]. For both AP-PA and left-right shifts calculated SD were always below 1 mm, except for patient #4, who was treated with a non-customized bolus that pushed the globe backwards in a random fashion. In ideal set-up conditions PTV margins around the target were estimated to be 3 mm. Asking patients to close their eyes is a simple and reliable immobilization procedure when treating ocular tumors with stereotactic radiotherapy. Margins of 3 mm around the target may be necessary to safely treat these tumors under ideal set-up conditions.
为评估使用专门用于立体定向放射治疗的基于微型多叶的直线加速器治疗的葡萄膜黑色素瘤患者闭眼时的可靠性和靶区定位可重复性。对连续5例接受葡萄膜黑色素瘤根治性放疗的患者，在治疗期间每2天进行一次重新模拟CT扫描以监测定位可重复性（共获得23次重新模拟CT数据）。所有患者在模拟前均接受眼眶MRI扫描，以帮助在模拟CT中确定目标和危及器官（如晶状体、视神经、睫状体和泪腺）（MRI到CT骨配准）。患者在闭眼状态下进行模拟、重新模拟和治疗。患者1接受5次每日分割照射，患者2至5接受10次每日分割照射。我们选择患眼的晶状体作为要控制的结构，假设晶状体的正确重新定位应是靶区重新定位正确性的有效替代指标。测量每位患者晶状体在三个轴向上的位移（平均值和标准差，SD）。计算系统误差和标准误差。根据麦肯齐等人的研究[《物理医学与生物学》45卷，3331 - 3342页（2000年）]估计计划靶区（PTV）边界。对于前后（AP - PA）和左右移位，计算得到的标准差除患者4外均始终低于1毫米，患者4使用的非定制填充物以随机方式将眼球向后推。在理想设置条件下，靶区周围的PTV边界估计为3毫米。在用立体定向放射治疗眼部肿瘤时，让患者闭眼是一种简单可靠的固定方法。在理想设置条件下，靶区周围3毫米的边界可能是安全治疗这些肿瘤所必需的。
