NCTeam, Strahlenklinik, Universitätsklinikum Essen, Essen, Germany.
Int J Radiat Oncol Biol Phys. 2012 Jul 15;83(4):1330-7. doi: 10.1016/j.ijrobp.2011.09.014. Epub 2012 Jan 13.
External beam radiotherapy is the only conservative curative approach for Stage I non-Hodgkin lymphomas of the conjunctiva. The target volume is geometrically complex because it includes the eyeball and lid conjunctiva. Furthermore, the target volume is adjacent to radiosensitive structures, including the lens, lacrimal glands, cornea, retina, and papilla. The radiotherapy planning and optimization requires accurate calculation of the dose in these anatomical structures that are much smaller than the structures traditionally considered in radiotherapy. Neither conventional treatment planning systems nor dosimetric measurements can reliably determine the dose distribution in these small irradiated volumes.
The Monte Carlo simulations of a Varian Clinac 2100 C/D and human eye were performed using the penelope and penEasyLinac codes. Dose distributions and dose volume histograms were calculated for the bulbar conjunctiva, cornea, lens, retina, papilla, lacrimal gland, and anterior and posterior hemispheres.
The simulated results allow choosing the most adequate treatment setup configuration, which is an electron beam energy of 6 MeV with additional bolus and collimation by a cerrobend block with a central cylindrical hole of 3.0 cm diameter and central cylindrical rod of 1.0 cm diameter.
Monte Carlo simulation is a useful method to calculate the minute dose distribution in ocular tissue and to optimize the electron irradiation technique in highly critical structures. Using a voxelized eye phantom based on patient computed tomography images, the dose distribution can be estimated with a standard statistical uncertainty of less than 2.4% in 3 min using a computing cluster with 30 cores, which makes this planning technique clinically relevant.
对于结膜Ⅰ期非霍奇金淋巴瘤，外照射放疗是唯一的保守治疗方法。靶区几何形状复杂，因为它包括眼球和眼睑结膜。此外，靶区毗邻包括晶状体、泪腺、角膜、视网膜和视乳头在内的放射敏感结构。放疗计划和优化需要准确计算这些解剖结构的剂量，这些结构比传统放疗中考虑的结构小得多。传统的治疗计划系统和剂量测量都不能可靠地确定这些小照射体积内的剂量分布。
使用 penelope 和 penEasyLinac 代码对瓦里安 Clinac 2100 C/D 和人眼进行了蒙特卡罗模拟。计算了球结膜、角膜、晶状体、视网膜、视乳头、泪腺以及前半球和后半球的剂量分布和剂量体积直方图。
模拟结果允许选择最合适的治疗设置配置，即 6 MeV 的电子束能量，外加中央圆柱形孔直径为 3.0 cm、中央圆柱形杆直径为 1.0 cm 的 Cerrobend 块进行额外的电子束增敏和准直。
蒙特卡罗模拟是计算眼部组织微小剂量分布和优化高度关键结构中电子照射技术的有用方法。使用基于患者计算机断层扫描图像的体素化眼睛模型，使用 30 核计算集群在 3 分钟内可以以小于 2.4%的标准统计不确定性估计剂量分布，这使得这种规划技术具有临床相关性。
