Javedan Khosrow, Stevens Craig W, Forster Kenneth M
Radiation Oncology, H. Lee Moffitt Cancer Center and Research Institute, and Radiation Oncology, Tampa, Florida, U.S.A.
H. Lee Moffitt Cancer Center and Research Institute at the University of South Florida, Tampa, Florida, U.S.A.
J Appl Clin Med Phys. 2008 Oct 29;9(4):98-109. doi: 10.1120/jacmp.v9i4.2799.
The present work investigated the potential of compensator-based intensity-modulated radiation therapy (CB-IMRT) as an alternative to multileaf collimator (MLC)-based intensity-modulated radiation therapy (IMRT) to treat malignant pleural mesothelioma (MPM) post extrapleural pneumonectomy. Treatment plans for 4 right-sided and 1 left-sided MPM post-surgery cases were generated using a commercial treatment planning system, XIO/CMS (Computerized Medical Systems, St. Louis, MO). We used a 7-gantry-angle arrangement with 6 MV beams to generate these plans. The maximum required field size was 30 x 40 cm. We evaluated IMRT plans with brass compensators (.Decimal, Sanford, FL) by examining isodose distributions, dose-volume histograms, metrics to quantify conformal plan quality, and homogeneity. Quality assurance was performed for one of the compensator plans. Conformal dose distributions were achieved with CB-IMRT for all 5 cases, the average planning target volume (PTV) coverage being 95.1% of the PTV volume receiving the full prescription dose. The average lung V20 (volume of lung receiving 20 Gy) was 1.8%, the mean lung dose was 6.7 Gy, and the average contralateral kidney V15 was 0.6%. The average liver dose V30 was 34.0% for the right-sided cases and 10% for the left-sided case. The average monitor units (MUs) per fraction were 980 MUs for the 45-Gy prescriptions (mean: 50 Gy) and 1083 MUs for the 50-Gy prescriptions (mean: 54 Gy). Post surgery, CB-IMRT for MPM is a feasible IMRT technique for treatment with a single isocenter. Compensator plans achieved dose objectives and were safely delivered on a Siemens Oncor machine (Siemens Medical Solutions, Malvern, PA). These plans showed acceptably conformal dose distributions as confirmed by multiple measurement techniques. Not all linear accelerators can deliver large-field MLC-based IMRT, but most can deliver a maximum conformal field of 40 x 40 cm. It is possible and reasonable to deliver IMRT with compensators for fields this size with most conventional linear accelerators.
本研究探讨了基于补偿器的调强放射治疗（CB-IMRT）作为基于多叶准直器（MLC）的调强放射治疗（IMRT）的替代方案，用于治疗胸膜外肺切除术后恶性胸膜间皮瘤（MPM）的潜力。使用商业治疗计划系统XIO/CMS（Computerized Medical Systems，圣路易斯，密苏里州）为4例右侧和1例左侧MPM术后病例生成治疗计划。我们使用7个机架角度配置和6MV射线来生成这些计划。最大所需射野尺寸为30×40cm。我们通过检查等剂量分布、剂量体积直方图、量化适形计划质量和均匀性的指标，评估了带有黄铜补偿器（.Decimal，桑福德，佛罗里达州）的IMRT计划。对其中一个补偿器计划进行了质量保证。所有5例病例通过CB-IMRT均实现了适形剂量分布，平均计划靶区（PTV）覆盖率为接受全处方剂量的PTV体积的95.1%。平均肺V20（接受20Gy剂量的肺体积）为1.8%，平均肺剂量为6.7Gy，平均对侧肾V15为0.6%。右侧病例的平均肝脏剂量V30为34.0%，左侧病例为10%。对于45Gy处方（平均：50Gy），每分次的平均监测单位（MUs）为980MUs，对于50Gy处方（平均：54Gy），为1083MUs。术后，CB-IMRT用于MPM治疗是一种可行的单等中心IMRT技术。补偿器计划实现了剂量目标，并在西门子Oncor机器（西门子医疗解决方案公司，马尔文，宾夕法尼亚州）上安全交付。这些计划通过多种测量技术证实显示出可接受的适形剂量分布。并非所有直线加速器都能进行基于大射野MLC的IMRT，但大多数能提供最大40×40cm的适形射野。使用大多数传统直线加速器为这种尺寸的射野配备补偿器来进行IMRT是可行且合理的。
