Astrahan M A, Luxton G, Jozsef G, Kampp T D, Liggett P E, Sapozink M D, Petrovich Z
Department of Radiation Oncology, University of Southern California School of Medicine, Los Angeles 90033.
Int J Radiat Oncol Biol Phys. 1990 Mar;18(3):679-87. doi: 10.1016/0360-3016(90)90077-w.
Brachytherapy using removable episcleral plaques containing sealed radioisotope sources is being studied as an alternative to enucleation in the treatment of choroidal melanoma and other tumors of the eye. Encouraging early results have been reported, but late complications which lead to loss of vision continue to be a problem. A randomized national study, the Collaborative Ocular Melanoma Study (COMS) is currently in progress to evaluate the procedure. The COMS specified isotope is 125I. Precise dosimetric calculations near the plaque may correlate strongly with complications and could also be used to optimize isotope loading patterns in the plaques. A microcomputer based treatment planning system has been developed for ophthalmic plaque brachytherapy. The program incorporates an interactive, 3-dimensional, solid-surface, color-graphic interface. The program currently supports 125I and 192Ir seeds which are treated as anisotropic line sources. Collimation effects related to plaque structure are accounted for, permitting detailed study of shielding effectiveness near the lip of a plaque. A dose distribution matrix may be calculated in any subregion of a transverse, sagittal, or coronal planar cross section of the eye, in any plane transecting the plaque and crossing the eye diametrically, or on a spherical surface within or surrounding the eye. Spherical surfaces may be displayed as 3-dimensional perspective projections or as funduscopic diagrams. Isodose contours are interpolated from the dose matrix. A pointer is also available to explicitly calculate and display dose at any location on the dosimetry surface. An interactive editing capability allows new plaque designs to be rapidly added to the system.
使用含有密封放射性同位素源的可移除巩膜外斑块进行近距离放射治疗，正作为眼球摘除术的替代方法，用于治疗脉络膜黑色素瘤和其他眼部肿瘤。已报告了令人鼓舞的早期结果，但导致视力丧失的晚期并发症仍然是一个问题。一项全国性随机研究——协作性眼黑色素瘤研究（COMS）目前正在进行，以评估该治疗方法。COMS指定的同位素是125I。斑块附近精确的剂量计算可能与并发症密切相关，也可用于优化斑块中的同位素加载模式。已开发出一种基于微型计算机的眼科斑块近距离放射治疗计划系统。该程序包含一个交互式的三维实体表面彩色图形界面。该程序目前支持将125I和192Ir种子视为各向异性线源进行处理。考虑了与斑块结构相关的准直效应，从而可以详细研究斑块边缘附近的屏蔽效果。可以在眼睛的横向、矢状或冠状平面横截面的任何子区域、在任何与斑块相交并沿眼球直径方向穿过眼球的平面中，或在眼球内部或周围的球面上计算剂量分布矩阵。球面可以显示为三维透视图或眼底图。等剂量线从剂量矩阵中插值得到。还可以使用指针在剂量测定表面的任何位置明确计算和显示剂量。交互式编辑功能允许将新的斑块设计快速添加到系统中。
