Penalization of aperture complexity in inversely planned volumetric modulated arc therapy
Penalization of aperture complexity in inversely planned volumetric modulated arc therapy
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DOI：
10.1118/1.4762566
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发表时间：
2012-11-01
期刊：
影响因子：
3.8
通讯作者：
Roberts, Donald A.
中科院分区：
文献类型：
--
作者：
Younge, Kelly C.;Matuszak, Martha M.;Roberts, Donald A.
目的：在体积调制式弧形治疗（VMAT）计划期间获得的放射线可能较小且不规则，导致输送期间剂量测定不准确。我们的目的是开发和集成一个孔径正则化目标函数到VMAT的优化过程中，并量化使用这个目标函数的剂量输送精度和优化的剂量distributions.Methods的影响：一个基于孔径的度量（“边缘惩罚”）开发，惩罚复杂的孔径形状的基础上的MLC侧边长度和孔径面积的比率。为了评估度量的效用，创建了VMAT计划，例如脊柱旁、脑和肝SBRT病例，在成本函数中包含和不包含边缘惩罚。为了研究剂量计算的准确性，使用Gafchromic EBT 2胶片单独测量15个最高加权孔径，并作为两个椎旁计划中每一个的组合：一个有边缘惩罚，一个没有边缘惩罚。使用三通道的非均匀性校正和测量进行了分析，直接比较calculation.Results：与边缘处罚产生的martures更大，更有规律的形状，需要高达30%的监视器比那些没有创建的边缘处罚单位。剂量体积直方图分析显示，靶点、危险器官和正常组织的剂量变化可忽略不计。用胶片测量的脊柱旁计划的边缘惩罚孔径显示出与计算不一致的像素数量明显减少10%以上。对于5%的剂量通过标准，在复合剂量分布的非边缘惩罚和边缘惩罚计划中通过的像素数分别为52%和96%。采用3%剂量/1 mm距离标准的伽马射线，两个计划的通过率分别为79.5%（无惩罚）/95.4%（有惩罚）。3%/1 mm的梯度补偿导致83.3%/96.2%passrate.Conclusions：在优化过程中使用的边缘惩罚有可能显着提高剂量输送精度为VMAT计划，同时仍然保持高品质的优化剂量分布。该惩罚规则化孔径形状并提高递送效率。(C)2012年美国医学物理学家协会。[http：//dx.doi.org/10.1118/1.4762566]
Purpose: Apertures obtained during volumetric modulated arc therapy (VMAT) planning can be small and irregular, resulting in dosimetric inaccuracies during delivery. Our purpose is to develop and integrate an aperture-regularization objective function into the optimization process for VMAT, and to quantify the impact of using this objective function on dose delivery accuracy and optimized dose distributions.Methods: An aperture-based metric ("edge penalty") was developed that penalizes complex aperture shapes based on the ratio of MLC side edge length and aperture area. To assess the utility of the metric, VMAT plans were created for example paraspinal, brain, and liver SBRT cases with and without incorporating the edge penalty in the cost function. To investigate the dose calculation accuracy, Gafchromic EBT2 film was used to measure the 15 highest weighted apertures individually and as a composite from each of two paraspinal plans: one with and one without the edge penalty applied. Films were analyzed using a triple-channel nonuniformity correction and measurements were compared directly to calculations.Results: Apertures generated with the edge penalty were larger, more regularly shaped and required up to 30% fewer monitor units than those created without the edge penalty. Dose volume histogram analysis showed that the changes in doses to targets, organs at risk, and normal tissues were negligible. Edge penalty apertures that were measured with film for the paraspinal plan showed a notable decrease in the number of pixels disagreeing with calculation by more than 10%. For a 5% dose passing criterion, the number of pixels passing in the composite dose distributions for the non-edge penalty and edge penalty plans were 52% and 96%, respectively. Employing gamma with 3% dose/1 mm distance criteria resulted in a 79.5% (without penalty)/95.4% (with penalty) pass rate for the two plans. Gradient compensation of 3%/1 mm resulted in 83.3%/96.2% pass rates.Conclusions: The use of the edge penalty during optimization has the potential to markedly improve dose delivery accuracy for VMAT plans while still maintaining high quality optimized dose distributions. The penalty regularizes aperture shape and improves delivery efficiency. (C) 2012 American Association of Physicists in Medicine. [http://dx.doi.org/10.1118/1.4762566]