Comparison of proton therapy treatment planning for head tumors with a pencil beam algorithm on dual and single energy CT images
Comparison of proton therapy treatment planning for head tumors with a pencil beam algorithm on dual and single energy CT images
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DOI：
10.1118/1.4939106
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发表时间：
2016-01-01
期刊：
影响因子：
3.8
通讯作者：
Landry, Guillaume
中科院分区：
文献类型：
--
作者：
Hudobivnik, Nace;Schwarz, Florian;Landry, Guillaume
目的：双能CT（DECT）最近被提出作为单能CT（SECT）的改进，用于质子治疗治疗计划（TP）的停止功率比（SPR）估计，从而潜在地减少范围的不确定性。已发表的文献研究了幻影。本研究的目的是在执行质子治疗TP SECT和DECT头部图像相同的患者，并在评估是否报告改善DECT SPR的准确性转化为临床相关的范围内的变化，在临床头部treatment scenaries.Methods：两个phantomy进行了扫描，在最后一代双源DECT扫描仪在90和150千伏特与锡过滤。第一个体模（Gammex体模）用于根据SPR校准扫描仪，而第二个体模用于评价（CIRS体模）。5例头部外伤患者的DECT图像被用作质子治疗TP的替代癌症患者图像。在SECT和DECT图像上执行基于双射束算法的TP，并使用Monte Carlo（MC）模拟平台计算与优化质子计划对应的剂量分布，对于从150 kVp图像转换获得的两个计划，使用相同的患者几何形状。从SECT和DECT计划的MC剂量分布之间的范围移位进行了评估，使用2D范围maps.Results：SPR根均方误差（RMSE）的Gammex体模的插入分别为1.9%，1.8%，和1.2%的SECT体模校准（SECTphantom），SECT化学计量校准（SECTchemoistically），和DECT校准，分别。对于CIRS体模，这些分别为3.6%、1.6%和1.0%。在研究患者解剖结构时，将SECT化学计量与DECT进行比较时，观察到头部病例的组中位范围差异高达-1.4%。对于该校准，5名患者的第25次和第75次校准值在-2%至0%之间变化。结论：首次采用铅笔束算法和DECT图像进行质子治疗TP。考虑到两个体模评价的DECT准确度为1.2%和1.0% RMSE，此处报告的范围差异是否显著值得怀疑。(C)2016年美国医学物理学家协会。
Purpose: Dual energy CT (DECT) has recently been proposed as an improvement over single energy CT (SECT) for stopping power ratio (SPR) estimation for proton therapy treatment planning (TP), thereby potentially reducing range uncertainties. Published literature investigated phantoms. This study aims at performing proton therapy TP on SECT and DECT head images of the same patients and at evaluating whether the reported improved DECT SPR accuracy translates into clinically relevant range shifts in clinical head treatment scenarios.Methods: Two phantoms were scanned at a last generation dual source DECT scanner at 90 and 150 kVp with Sn filtration. The first phantom (Gammex phantom) was used to calibrate the scanner in terms of SPR while the second served as evaluation (CIRS phantom). DECT images of five head trauma patients were used as surrogate cancer patient images for TP of proton therapy. Pencil beam algorithm based TP was performed on SECT and DECT images and the dose distributions corresponding to the optimized proton plans were calculated using a Monte Carlo (MC) simulation platform using the same patient geometry for both plans obtained from conversion of the 150 kVp images. Range shifts between the MC dose distributions from SECT and DECT plans were assessed using 2D range maps.Results: SPR root mean square errors (RMSEs) for the inserts of the Gammex phantom were 1.9%, 1.8%, and 1.2% for SECT phantom calibration (SECTphantom), SECT stoichiometric calibration (SECTstoichiometric), and DECT calibration, respectively. For the CIRS phantom, these were 3.6%, 1.6%, and 1.0%. When investigating patient anatomy, group median range differences of up to -1.4% were observed for head cases when comparing SECTstoichiometric with DECT. For this calibration the 25th and 75th percentiles varied from -2% to 0% across the five patients. The group median was found to be limited to 0.5% when using SECTphantom and the 25th and 75th percentiles varied from -1% to 2%.Conclusions: Proton therapy TP using a pencil beam algorithm and DECT images was performed for the first time. Given that the DECT accuracy as evaluated by two phantoms was 1.2% and 1.0% RMSE, it is questionable whether the range differences reported here are significant. (C) 2016 American Association of Physicists in Medicine.