Iskanderani Omar, Béliveau-Nadeau Dominique, Doucet Robert, Coulombe Geneviève, Pascale Deborah, Roberge David
1 Department of Radiation Oncology, Centre Hospitalier de l'Université de Montréal (CHUM), Montréal, Québec, Canada.
2 Department of Radiation Oncology, King Abdulaziz University Hospital, Jeddah, Saudi Arabia.
Technol Cancer Res Treat. 2017 Jun;16(3):352-356. doi: 10.1177/1533034617690979. Epub 2017 Feb 7.
Our preferred treatment for juxtapapillary choroidal melanoma is stereotactic radiotherapy. We aim to describe our immobilization system and quantify its reproducibility.
Patients were identified in our radiosurgery database. Patients were imaged at computed tomography simulator with an in-house system which allows visual monitoring of the eye as the patient fixates a small target. All patients were reimaged at least once prior to and/or during radiotherapy. The patients were treated on the CyberKnife system, 60 Gy in 10 daily fractions, using skull tracking in conjunction with our visual monitoring system. In order to quantify the reproducibility of the eye immobilization system, computed tomography scans were coregistered using rigid 6-dimensional skull registration. Using the coregistered scans, x, y, and z displacements of the lens/optic nerve insertion were measured. From these displacements, 3-dimensional vectors were calculated.
Thirty-four patients were treated from October 2010 to September 2015. Thirty-nine coregistrations were performed using 73 scans (2-3 scans per patient). The mean displacements of lens and optic nerve insertion were 0.1 and 0.0 mm. The median 3-dimensional displacements (absolute value) of lens and nerve insertion were 0.8 and 0.7 mm (standard deviation: 0.5 and 0.6 mm). Ninety-eight percent of 3-dimensional displacements were below 2 mm (maximum 2.4 mm). The calculated planning target volume (PTV) margins were 0.8, 1.4, and 1.5 mm in the anterior-posterior, craniocaudal, and right-left axes, respectively. Following this analysis, no further changes have been applied to our planning margin of 2 to 2.5 mm as it is also meant to account for uncertainties in magnetic resonance imaging to computed tomography registration, skull tracking, and also contouring variability.
We have found our stereotactic eye immobilization system to be highly reproducible (<1 mm) and free of systematic error.
我们对毗邻视乳头的脉络膜黑色素瘤的首选治疗方法是立体定向放射治疗。我们旨在描述我们的固定系统并量化其可重复性。
在我们的放射外科数据库中识别患者。患者在计算机断层扫描模拟器上使用内部系统进行成像，该系统可在患者注视小目标时对视眼进行视觉监测。所有患者在放射治疗前和/或期间至少重新成像一次。患者在射波刀系统上接受治疗，分10次每日剂量给予60 Gy，使用颅骨追踪结合我们的视觉监测系统。为了量化眼部固定系统的可重复性，使用刚性6维颅骨配准对计算机断层扫描进行配准。利用配准后的扫描，测量晶状体/视神经插入点的x、y和z位移。根据这些位移计算三维向量。
2010年10月至2015年9月期间治疗了34例患者。使用73次扫描（每位患者2 - 3次扫描）进行了39次配准。晶状体和视神经插入点的平均位移分别为0.1和0.0 mm。晶状体和神经插入点的三维位移中位数（绝对值）为0.8和0.7 mm（标准差：0.5和0.6 mm）。98%的三维位移低于2 mm（最大2.4 mm）。计算得出的计划靶体积（PTV）在前后、头尾和左右轴上的边界分别为0.8、1.4和1.5 mm。经过此分析后，我们2至2.5 mm的计划边界未再做进一步调整，因为它还考虑到了磁共振成像到计算机断层扫描配准、颅骨追踪以及轮廓勾画变异性中的不确定性。
我们发现我们的立体定向眼部固定系统具有高度可重复性（<1 mm）且无系统误差。
