Jamema Swamidas V, Sharma Pramod K, Sharma Dayananda, Laskar Siddhartha, Deshpande Deepak D, Shrivastava Shyam K
Department of Medical Physics, Tata Memorial Hospital, Parel, Mumbai, India.
J Cancer Res Ther. 2009 Oct-Dec;5(4):240-6. doi: 10.4103/0973-1482.59893.
A three dimensional (3D) image-based dosimetric study to quantitatively compare geometric vs. dose-point optimization in combination with graphical optimization for interstitial brachytherapy of soft tissue sarcoma (STS).
Fifteen consecutive STS patients, treated with intra-operative, interstitial Brachytherapy, were enrolled in this dosimetric study. Treatment plans were generated using dose points situated at the "central plane between the catheters", "between the catheters throughout the implanted volume", at "distances perpendicular to the implant axis" and "on the surface of the target volume" Geometrically optimized plans had dose points defined between the catheters, while dose-point optimized plans had dose points defined at a plane perpendicular to the implant axis and on the target surface. Each plan was graphically optimized and compared using dose volume indices.
Target coverage was suboptimal with coverage index (CI = 0.67) when dose points were defined at the central plane while it was superior when the dose points were defined at the target surface (CI=0.93). The coverage of graphically optimized plans (GrO) was similar to non-GrO with dose points defined on surface or perpendicular to the implant axis. A similar pattern was noticed with conformity index (0.61 vs. 0.82). GrO were more conformal and less homogeneous compared to non-GrO. Sum index was superior for dose points defined on the surface of the target and relatively inferior for plans with dose points at other locations (1.35 vs. 1.27).
Optimization with dose points defined away from the implant plane and on target results in superior target coverage with optimal values of other indices. GrO offer better target coverage for implants with non-uniform geometry and target volume.
进行一项基于三维（3D）图像的剂量学研究，以定量比较软组织肉瘤（STS）间质近距离治疗中几何优化与剂量点优化结合图形优化的效果。
本剂量学研究纳入了15例接受术中间质近距离治疗的连续STS患者。使用位于“导管之间的中心平面”、“植入体积内导管之间”、“垂直于植入轴的距离处”以及“靶体积表面”的剂量点生成治疗计划。几何优化计划在导管之间定义剂量点，而剂量点优化计划在垂直于植入轴的平面和靶表面定义剂量点。每个计划都进行图形优化，并使用剂量体积指数进行比较。
当在中心平面定义剂量点时，靶区覆盖欠佳，覆盖指数（CI = 0.67），而当在靶表面定义剂量点时则更佳（CI = 0.93）。在表面或垂直于植入轴定义剂量点时，图形优化计划（GrO）的覆盖情况与非图形优化计划相似。适形指数也有类似模式（0.61对0.82）。与非图形优化计划相比，图形优化计划的适形性更好但均匀性较差。总和指数在靶表面定义剂量点时更佳，在其他位置定义剂量点的计划中相对较差（1.35对1.27）。
在远离植入平面且在靶区定义剂量点进行优化可实现更好的靶区覆盖，同时其他指数的值也较为理想。对于几何形状和靶体积不均匀的植入，图形优化可提供更好的靶区覆盖。
