Cormack R A, Kooy H M, Bellerive M R, Loeffler J S, Petersen R A, Tarbell N J
Department of Radiation Oncology, Harvard Medical School, Boston, Massachusetts 02215, USA.
Med Phys. 1998 Aug;25(8):1438-42. doi: 10.1118/1.598317.
The proximity of the lens to the retina makes the treatment of retinoblastoma a challenge for external beam radiation therapy. The approximately 1 mm separation between the posterior edge of the lens and the anterior region of the retina causes a trade-off between coverage of the entire retina and excessive dose to the lens. A stereotactic, LINAC based, lens sparing technique for treating retinoblastoma is presented. The technique uses noncoplanar arcs with the lens at isocenter. A special noncircular collimator blocks the lens but it also causes the dose distribution to vary across the retina. A fluence modulation filter is used to reduce the dose inhomogeneity across the target. The resulting dose distribution is roughly hemispheric, providing both anterior coverage of the retina and lens blocking unlike conventional techniques. The method used to develop the collimator and filter assembly is presented. Dosimetry of the assembly was carried out using radiochromic film, and the results were entered in a treatment planning system. The dose distribution as measured in a phantom is provided and compared to calculations.
晶状体与视网膜距离较近，这使得视网膜母细胞瘤的外照射放疗成为一项挑战。晶状体后缘与视网膜前部区域之间约1毫米的间距导致在整个视网膜覆盖范围与晶状体接受过量剂量之间存在权衡。本文介绍了一种基于直线加速器的立体定向晶状体保留技术用于治疗视网膜母细胞瘤。该技术使用非共面弧，将晶状体置于等中心。一种特殊的非圆形准直器可遮挡晶状体，但这也会导致视网膜上的剂量分布发生变化。使用通量调制滤过器来减少靶区的剂量不均匀性。最终的剂量分布大致呈半球形，与传统技术不同，它既能提供视网膜前部覆盖，又能遮挡晶状体。本文介绍了用于开发准直器和滤过器组件的方法。使用放射变色胶片对该组件进行剂量测定，并将结果输入治疗计划系统。给出了在体模中测量的剂量分布，并与计算结果进行比较。
