A new metric for assessing IMRT modulation complexity and plan deliverability
A new metric for assessing IMRT modulation complexity and plan deliverability
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DOI：
10.1118/1.3276775
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发表时间：
2010-02-01
期刊：
影响因子：
3.8
通讯作者：
Purdie, Thomas G.
中科院分区：
文献类型：
--
作者：
McNiven, Andrea L.;Sharpe, Michael B.;Purdie, Thomas G.
研究方法：已完成多部位（乳腺、直肠、前列腺、前列腺床、肺和头颈部）和部位特异性（肺）剂量测定评价。计算每个射束和总体治疗计划的MCS。使用2D二极管阵列（MapleTM，Sun Nuclear，墨尔本，FL）来获得每个光束的测量值。测量和计划剂量（PINNACLE 3，菲利普斯，麦迪逊，WI）使用不同的差异百分比和一致性距离（DTA）标准进行评价（3%/3 mm和2%/1 mm）以及剂量测定结果与复杂性之间的关系（通过MCS或简单光束参数测量）。结果：对于多站点分析（共243个计划），每个治疗部位的平均MCS评分为乳腺（0.92）、直肠（0.858）、前列腺（0.837）、前列腺床（0.652）、肺（0.631）和头颈部（0.356）。MCS允许汇编治疗部位特定的统计数据，这对于比较不同的技术以及比较具有典型复杂性水平的个体治疗计划是有用的。对于选择用于剂量测定的6个计划，对于3%/3 mm评价标准，平均二极管通过率百分比为98.7%（最小值为96%）。计划剂量和测量剂量之间绝对剂量测量的平均差异为1.7 cGy。详细的肺部分析还显示，测量剂量和计划剂量之间具有极好的一致性，因为所有射束的二极管通过率（3%/3 mm标准）均大于95.9%，平均通过率为99.0%。肺计划的平均绝对最大剂量差为0.7 cGy。MCS和简单波束参数之间没有直接相关性，简单波束参数可以用作复杂度水平的替代（即，段数或MU）。2%/1 mm的评价标准可靠地允许识别剂量稳健的射束。在本研究中，我们将稳健射束或计划定义为在2%/1 mm处保持二极管通过率大于90%的射束或计划，表明即使在更严格的评价标准下，与计划剂量相比，输送也被视为准确。MCS和MU阈值标准通过定义所需的特异性1.0来确定。MCS阈值为0.8，可识别稳健的可输送性，灵敏度为0.36。相比之下，MU有一个较低的灵敏度为0.23的阈值为50 MU.Conclusions：MCS允许定量评估计划的复杂性，在一个固定的规模，可以应用于所有的治疗部位，可以提供更多的信息，剂量输送比简单的光束参数。这在整个治疗计划和QA过程中可能是有用的。
Methods: A multisite (breast, rectum, prostate, prostate bed, lung, and head and neck) and site-specific (lung) dosimetric evaluation has been completed. The MCS was calculated for each beam and the overall treatment plan. A 2D diode array (MapCHECK (TM), Sun Nuclear, Melbourne, FL) was used to acquire measurements for each beam. The measured and planned dose (PINNACLE3, Phillips, Madison, WI) was evaluated using different percent differences and distance to agreement (DTA) criteria (3%/3 mm and 2%/1 mm) and the relationship between the dosimetric results and complexity (as measured by the MCS or simple beam parameters) assessed.Results: For the multisite analysis (243 plans total), the mean MCS scores for each treatment site were breast (0.92), rectum (0.858), prostate (0.837), prostate bed (0.652), lung (0.631), and head and neck (0.356). The MCS allowed for compilation of treatment site-specific statistics, which is useful for comparing different techniques, as well as for comparison of individual treatment plans with the typical complexity levels. For the six plans selected for dosimetry, the average diode percent pass rate was 98.7% (minimum of 96%) for 3%/3 mm evaluation criteria. The average difference in absolute dose measurement between the planned and measured dose was 1.7 cGy. The detailed lung analysis also showed excellent agreement between the measured and planned dose, as all beams had a diode percentage pass rate for 3%/3 mm criteria of greater than 95.9%, with an average pass rate of 99.0%. The average absolute maximum dose difference for the lung plans was 0.7 cGy. There was no direct correlation between the MCS and simple beam parameters which could be used as a surrogate for complexity level (i.e., number of segments or MU). An evaluation criterion of 2%/1 mm reliably allowed for the identification of beams that are dosimetrically robust. In this study we defined a robust beam or plan as one that maintained a diode percentage pass rate greater than 90% at 2%/1 mm, indicating delivery that was deemed accurate when compared to the planned dose, even under stricter evaluation criterion. MCS and MU threshold criteria were determined by defining a required specificity of 1.0. A MCS threshold of 0.8 allowed for identification of robust deliverability with a sensitivity of 0.36. In contrast, MU had a lower sensitivity of 0.23 for a threshold of 50 MU.Conclusions: The MCS allows for a quantitative assessment of plan complexity, on a fixed scale, that can be applied to all treatment sites and can provide more information related to dose delivery than simple beam parameters. This could prove useful throughout the entire treatment planning and QA process.