Department of Radiation Oncology, Stanford University School of Medicine, 875 Blake Wilbur Drive, Stanford, CA 94305-5847.
Technol Cancer Res Treat. 2010 Dec;9(6):629-36. doi: 10.1177/153303461000900611.
To establish an inverse planning framework with adjustable voxel penalty for more conformal IMRT dose distribution as well as improved interactive controllability over the regional dose distribution of the resultant plan.
In the proposed coarse-to-fine planning scheme, a conventional inverse planning with organ specific parameters is first performed. The voxel penalty scheme is then "switched on" by allowing the prescription dose to change on an individual voxel scale according to the deviation of the actual voxel dose from the ideally desired dose. The rationale here is intuitive: when the dose at a voxel does not meet its ideal dose, it simply implies that this voxel is not competitive enough when compared with the ones that have met their planning goal. In this case, increasing the penalty of the voxel by varying the prescription can boost its competitiveness and thus improve its dose. After the prescription adjustment, the plan is re-optimized. The dose adjustment/re-optimization procedure is repeated until the resultant dose distribution cannot be improved anymore. The prescription adjustment on a finer scale can be accomplished either automatically or manually. In the latter case, the regions/voxels where a dose improvement is needed are selected visually, unlike in the automatic case where the selection is done purely based on the difference of the actual dose at a given voxel and its ideal prescription. The performance of the proposed method is evaluated using a head and neck and a prostate case.
An inverse planning framework with the voxel-specific penalty is established. By adjusting voxel prescriptions iteratively to boost the region where large mismatch between the actual calculated and desired doses occurs, substantial improvements can be achieved in the final dose distribution. The proposed method is applied to a head and neck case and a prostate case. For the former case, a significant reduction in the maximum dose to the brainstem is achieved while the PTV dose coverage is greatly improved. The doses to other organs at risk are also reduced, ranging from 10% to 30%. For the prostate case, the use of the voxel penalty scheme also results in vast improvements to the final dose distribution. The PTV experiences improved dose uniformity and the mean dose to the rectum and bladder is reduced by as much as 15%.
Introduction of the spatially non-uniform and adjustable prescription provides room for further improvements of currently achievable dose distributions and equips the planner with an effective tool to modify IMRT dose distributions interactively. The technique is easily implementable in any existing inverse planning platform, which should facilitate clinical IMRT planning process and, in future, off-line/on-line adaptive IMRT.
建立一个具有可调节体素惩罚的逆规划框架，以实现更适形的调强放疗剂量分布，并提高对计划区域剂量分布的交互可控性。
在提出的粗到精规划方案中，首先进行具有器官特异性参数的常规逆规划。然后，通过允许根据实际体素剂量与理想剂量的偏差在个体体素尺度上改变处方剂量，“开启”体素惩罚方案。这里的基本原理是直观的：当体素的剂量不符合其理想剂量时，这仅仅意味着与已经达到规划目标的体素相比，该体素的竞争力不足。在这种情况下，通过改变处方来增加体素的惩罚可以提高其竞争力，从而提高其剂量。处方调整后，重新优化计划。重复进行剂量调整/重新优化过程，直到无法进一步改善剂量分布为止。可以自动或手动完成更精细的尺度上的处方调整。在后一种情况下，需要剂量改善的区域/体素是通过视觉选择的，而不是在自动情况下，仅根据给定体素的实际剂量与其理想处方之间的差异进行选择。使用头颈部和前列腺病例评估了所提出方法的性能。
建立了具有体素特异性惩罚的逆规划框架。通过迭代调整体素处方来增强实际计算剂量与理想剂量之间存在较大差异的区域，可以显著改善最终剂量分布。将所提出的方法应用于头颈部和前列腺病例。对于前者，脑干的最大剂量显著降低，同时大大提高了 PTV 的剂量覆盖。其他危及器官的剂量也降低了 10%至 30%。对于前列腺病例，体素惩罚方案的使用也导致最终剂量分布有了很大的改善。PTV 体验到改善的剂量均匀性，直肠和膀胱的平均剂量降低了 15%。
引入空间非均匀和可调节的处方为进一步改善当前可实现的剂量分布提供了空间，并为规划师提供了一种有效的工具，可通过交互方式修改调强放疗剂量分布。该技术易于在任何现有的逆规划平台中实现，这将有助于临床调强放疗计划过程，并在未来实现离线/在线自适应调强放疗。
