McGarry Conor K, Bokrantz Rasmus, O'Sullivan Joe M, Hounsell Alan R
Radiotherapy Physics, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Belfast, Northern Ireland, UK.
Optimization and Systems Theory, KTH Royal Institute of Technology, Stockholm, Sweden; RaySearch Laboratories, Stockholm, Sweden.
Med Dosim. 2014 Autumn;39(3):205-11. doi: 10.1016/j.meddos.2014.02.002. Epub 2014 Mar 12.
Efficacy of inverse planning is becoming increasingly important for advanced radiotherapy techniques. This study's aims were to validate multicriteria optimization (MCO) in RayStation (v2.4, RaySearch Laboratories, Sweden) against standard intensity-modulated radiation therapy (IMRT) optimization in Oncentra (v4.1, Nucletron BV, the Netherlands) and characterize dose differences due to conversion of navigated MCO plans into deliverable multileaf collimator apertures. Step-and-shoot IMRT plans were created for 10 patients with localized prostate cancer using both standard optimization and MCO. Acceptable standard IMRT plans with minimal average rectal dose were chosen for comparison with deliverable MCO plans. The trade-off was, for the MCO plans, managed through a user interface that permits continuous navigation between fluence-based plans. Navigated MCO plans were made deliverable at incremental steps along a trajectory between maximal target homogeneity and maximal rectal sparing. Dosimetric differences between navigated and deliverable MCO plans were also quantified. MCO plans, chosen as acceptable under navigated and deliverable conditions resulted in similar rectal sparing compared with standard optimization (33.7 ± 1.8 Gy vs 35.5 ± 4.2 Gy, p = 0.117). The dose differences between navigated and deliverable MCO plans increased as higher priority was placed on rectal avoidance. If the best possible deliverable MCO was chosen, a significant reduction in rectal dose was observed in comparison with standard optimization (30.6 ± 1.4 Gy vs 35.5 ± 4.2 Gy, p = 0.047). Improvements were, however, to some extent, at the expense of less conformal dose distributions, which resulted in significantly higher doses to the bladder for 2 of the 3 tolerance levels. In conclusion, similar IMRT plans can be created for patients with prostate cancer using MCO compared with standard optimization. Limitations exist within MCO regarding conversion of navigated plans to deliverable apertures, particularly for plans that emphasize avoidance of critical structures. Minimizing these differences would result in better quality treatments for patients with prostate cancer who were treated with radiotherapy using MCO plans.
逆向计划的有效性对于先进放疗技术而言正变得愈发重要。本研究的目的是在RayStation（版本2.4，瑞典RaySearch Laboratories公司）中验证多标准优化（MCO）相对于Oncentra（版本4.1，荷兰Nucletron BV公司）中的标准调强放射治疗（IMRT）优化，并描述将导航式MCO计划转换为可交付的多叶准直器孔径所导致的剂量差异。使用标准优化和MCO为10例局限性前列腺癌患者创建了静态调强放射治疗计划。选择具有最小平均直肠剂量的可接受标准IMRT计划与可交付的MCO计划进行比较。对于MCO计划，通过一个用户界面来进行权衡，该界面允许在基于注量的计划之间进行连续导航。沿着最大靶区均匀性和最大直肠保护之间的轨迹，以递增步骤使导航式MCO计划可交付。还对导航式和可交付的MCO计划之间的剂量学差异进行了量化。在导航和可交付条件下被选为可接受的MCO计划，与标准优化相比，在直肠保护方面结果相似（33.7±1.8 Gy对35.5±4.2 Gy，p = 0.117）。随着对直肠回避给予更高优先级，导航式和可交付的MCO计划之间的剂量差异增大。如果选择了最佳的可交付MCO计划，与标准优化相比，观察到直肠剂量显著降低（30.6±1.4 Gy对35.5±4.2 Gy，p = 0.047）。然而，在一定程度上，改进是以剂量分布的适形性降低为代价的，这导致在3个耐受水平中的2个水平下膀胱接受的剂量显著更高。总之，与标准优化相比，使用MCO可为前列腺癌患者创建相似的IMRT计划。MCO在将导航式计划转换为可交付孔径方面存在局限性，特别是对于强调避免关键结构的计划。最小化这些差异将为使用MCO计划进行放射治疗的前列腺癌患者带来质量更好的治疗。
