Cherenkov imaging method for rapid optimization of clinical treatment geometry in total skin electron beam therapy
Cherenkov imaging method for rapid optimization of clinical treatment geometry in total skin electron beam therapy
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DOI：
10.1118/1.4939880
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发表时间：
2016-02-01
期刊：
影响因子：
3.8
通讯作者：
Jarvis, Lesley A.
中科院分区：
文献类型：
--
作者：
Andreozzi, Jacqueline M.;Zhang, Rongxiao;Jarvis, Lesley A.
目的：开发了一种方法，利用切伦科夫成像的两个机架的角度，产生最均匀的治疗平面在双场全皮肤电子束治疗（TSET）。方法：切伦科夫成像实施收集相对表面剂量从6 MeV的电子束在一个白色聚乙烯片的二维测量。一个增强的电荷耦合器件相机的时间门控直线加速器用于切伦科夫发射成像在62个不同的机架角度（1增量，从239.5到300.5）。根据改良的斯坦福大学TSET技术，该技术在每个患者位置使用两个射野进行全身覆盖，将合成图像创建为纸张上两个射束图像的总和;评价每个角度对在患者感兴趣区域的最小变化。Cherenkov与剂量的相关性与电离室测量进行了验证。在源到表面距离（SSD）= 441、370.5和300 cm处重复该过程，以确定不同房间几何形状的最佳角度扩展。此外，三名患者接受TSET使用修改后的斯坦福大学六双场技术与6兆电子伏的电子束在SSD = 441 cm成像treatment.Results：如在以前的研究中，切伦科夫强度被证明与剂量直接相关的均匀平坦phantomy（R2 = 0.93），使切伦科夫成像适当的候选人，以评估和优化TSET设置几何形状。该方法提供了密集的2D图像，允许从62个单个图像的一个数据集全面分析1891种可能的治疗几何形状。在SSD = 441 cm时，其机构TSET历史上使用的机架角度分别为255.5和284.5;然而，为最大均匀性优化的角度为252.5和287.5（角度扩展增加+6）。电离室测量证实了治疗野剂量均匀性的改善，从初始角度的24.4%到角度优化后的仅9.8%。观察到角度扩展和SSD之间的线性关系，范围从441 cm处的35到300 cm处的39，中线处的X线深度剂量无显著变化（R2 = 0.998）。对于病人的研究，影响因素在体内切伦科夫强度和测量表面dose之间的相关性仍在调查。结论：切伦科夫强度相关的相对剂量测量深度的最大剂量在一个统一的，平坦的幻影。因此，与热释光剂量计或电离室相比，体模成像可用于更广泛和更快速地分析和优化TSET治疗几何形状。这项工作表明，切伦科夫成像可以作为一种有效改善治疗方案的工具，并作为一种潜在的验证工具，用于对独特的患者治疗进行常规监测。(C)2016年美国医学物理学家协会。
Purpose: A method was developed utilizing Cherenkov imaging for rapid and thorough determination of the two gantry angles that produce the most uniform treatment plane during dual-field total skin electron beam therapy (TSET).Methods: Cherenkov imaging was implemented to gather 2D measurements of relative surface dose from 6 MeV electron beams on a white polyethylene sheet. An intensified charge-coupled device camera time-gated to the Linac was used for Cherenkov emission imaging at sixty-two different gantry angles (1 increments, from 239.5 to 300.5). Following a modified Stanford TSET technique, which uses two fields per patient position for full body coverage, composite images were created as the sum of two beam images on the sheet; each angle pair was evaluated for minimum variation across the patient region of interest. Cherenkov versus dose correlation was verified with ionization chamber measurements. The process was repeated at source to surface distance (SSD) = 441, 370.5, and 300 cm to determine optimal angle spread for varying room geometries. In addition, three patients receiving TSET using a modified Stanford six-dual field technique with 6 MeV electron beams at SSD = 441 cm were imaged during treatment.Results: As in previous studies, Cherenkov intensity was shown to directly correlate with dose for homogenous flat phantoms (R2 = 0.93), making Cherenkov imaging an appropriate candidate to assess and optimize TSET setup geometry. This method provided dense 2D images allowing 1891 possible treatment geometries to be comprehensively analyzed from one data set of 62 single images. Gantry angles historically used for TSET at their institution were 255.5 and 284.5 at SSD = 441 cm; however, the angles optimized for maximum homogeneity were found to be 252.5 and 287.5 (+6 increase in angle spread). Ionization chamber measurements confirmed improvement in dose homogeneity across the treatment field from a range of 24.4% at the initial angles, to only 9.8% with the angles optimized A linear relationship between angle spread and SSD was observed, ranging from 35 at 441 cm, to 39 at 300 cm, with no significant variation in percent-depth dose at midline (R2 = 0.998). For patient studies, factors influencing in vivo correlation between Cherenkov intensity and measured surface dose are still being investigated.Conclusions: Cherenkov intensity correlates to relative dose measured at depth of maximum dose in a uniform, flat phantom. Imaging of phantoms can thus be used to analyze and optimize TSET treatment geometry more extensively and rapidly than thermoluminescent dosimeters or ionization chambers. This work suggests that there could be an expanded role for Cherenkov imaging as a tool to efficiently improve treatment protocols and as a potential verification tool for routine monitoring of unique patient treatments. (C) 2016 American Association of Physicists in Medicine.