Quantification of the impact of MLC modeling and tissue heterogeneities on dynamic IMRT dose calculations
Quantification of the impact of MLC modeling and tissue heterogeneities on dynamic IMRT dose calculations
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DOI：
10.1118/1.2712413
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发表时间：
2007-04-01
期刊：
影响因子：
3.8
通讯作者：
Siebers, J. V.
中科院分区：
文献类型：
--
作者：
Mihaylov, I. B.;Lerma, F. A.;Siebers, J. V.
本研究量化了动态调强放射治疗剂量计算中的剂量预测误差（DPE），这些误差源于（a）使用强度矩阵来估计多叶准直器（MLC）调制光子通量（DPEIGfluence），而不是明确的MLC粒子输运，以及（B）通过叠加/卷积（SC）和笔形射束（PB）剂量计算算法处理组织异质性（DPEheterogeneities）。蒙特卡罗（MC）计算剂量用作参考标准。研究了18个头颈部动态MLC调强放射治疗计划。通过比较98% GTV（GTV D-98%）、CTV D-95%、结节D-90%、脊髓和脑干D-02%、腮腺D-50%、腮腺平均剂量（D-Mean）和上述结构的广义等效均匀剂量（gEUD）所接收的剂量来评估DPE。对于MC生成的强度网格，所有目标和关键结构的DPEIG通量均在2.1%以内。SC算法DPEhetero对于98.3%的被记录的指数在3%以内，并且对于所有被记录的指数在+/- 3.4%以内。PB算法DPEhetero在92%的统计指数中在3%以内。统计等效性检验表明，PB DPEhetero需要3.6%的区间来说明与MC标准品的等效性，而SC DPEhetero和DPEIGfluence的区间< 1.5%。总体而言，这些结果表明，SC和MC IMRT剂量计算，使用MC导出的强度矩阵的通量预测不引入显着的剂量误差相比，完整的蒙特卡罗剂量计算，但是，PB算法可能会导致临床上显着的剂量偏差。(c)2007年美国医学物理学家协会。
This study quantifies the dose prediction errors (DPEs) in dynamic IMRT dose calculations resulting from (a) use of an intensity matrix to estimate the multi-leaf collimator (MLC) modulated photon fluence (DPEIGfluence) instead of an explicit MLC particle transport, and (b) handling of tissue heterogeneities (DPEhetero) by superposition/convolution (SC) and pencil beam (PB) dose calculation algorithms. Monte Carlo (MC) computed doses are used as reference standards. Eighteen head-and-neck dynamic MLC IMRT treatment plans are investigated. DPEs are evaluated via comparing the dose received by 98% of the GTV (GTV D-98%), the CTV D-95%, the nodal D-90%, the cord and the brainstem D-02%, the parotid D-50%, the parotid mean dose (D-Mean), and generalized equivalent uniform doses (gEUDs) for the above structures. For the MC-generated intensity grids, DPEIGfluence is within 2.1% for all targets and critical structures. The SC algorithm DPEhetero is within 3% for 98.3% of the indices tallied, and within +/- 3.4% for all of the tallied indices. The PB algorithm DPEhetero is within 3% for 92% of the tallied indices. Statistical equivalence tests indicate that PB DPEhetero requires a 3.6% interval to state equivalence with the MC standard, while the intervals are < 1.5% for SC DPEhetero and DPEIGfluence. Overall, these results indicate that SC and MC IMRT dose calculations which use MC-derived intensity matrices for fluence prediction do not introduce significant dose errors compared with full Monte Carlo dose computations; however, PB algorithms may result in clinically significant dose deviations. (c) 2007 American Association of Physicists in Medicine.