Treatment plans optimization for contrast-enhanced synchrotron stereotactic radiotherapy
Treatment plans optimization for contrast-enhanced synchrotron stereotactic radiotherapy
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DOI：
10.1118/1.3327455
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发表时间：
2010-06-01
期刊：
影响因子：
3.8
通讯作者：
Adam, J. F.
中科院分区：
文献类型：
--
作者：
Edouard, M.;Broggio, D.;Adam, J. F.
目的：同步加速器立体定向放射治疗（SSRT）是一种治疗方法，涉及将高Z元素靶向肿瘤，然后用来自同步加速器源的单色X射线进行立体定向照射，以最佳能量调谐。照射几何形状，以及由高Z原子上的中等能量X射线以较高产率产生的次级粒子（特征X射线、光电子和俄歇电子），在肿瘤中产生局部剂量增强。在过去的六年里，该团队成功开发了全身注射碘化造影剂的碘增强SSRT，目前正在转移到临床试验中。这项工作的目的是研究的对比剂的类型，光束质量，照射的几何形状，并定义一个优化的SSRT treatment planne.Methods的光束加权的SSRT治疗的影响：理论剂量测定进行使用MCNPX粒子传输代码。模拟的几何形状是代表人类头部的理想化体模。将虚拟目标定位在体模的中心部分或偏离中心4 cm。作者研究了各种造影剂（碘、钆和金）和不同射束质量（来自同步加速器源的单色X射线束（30-120 keV）、来自X射线管的多色X射线束（80、120和180 kVp）和来自线性加速器的6 MV X射线束）的SSRT剂量测定特性。研究了三种照射几何形状：一个弧或三个非共面弧动态弧治疗，以及有限数量的光束照射。由此产生的剂量增强，光束轮廓，和直方图剂量体积进行了比较碘增强SSRT。尝试通过加权有限的X射线束来优化照射方案。最后，对患者的具体三维CT数据对比剂infration.Results：它被证明在这项研究中，一个80 keV的光束能量是一个很好的妥协，用于治疗人类脑肿瘤与碘增强SSRT，导致仍然高剂量增强因子（约2）和一个上级骨保存相比，较低的能量X射线。这种光束可以很容易地在欧洲同步辐射设施医疗光束线产生。此外，当使用单色X射线而不是来自传统管的多色X射线时，输送到骨的剂量显著减少。数据显示，与高能量治疗相比，碘SSRT表现出对脑健康组织的上级保护。波束加权优化显着提高了偏心肿瘤的治疗计划，相比nonweighted irradiations.Conclusions：这项研究表明了现实的临床计划的可行性低能量单色X射线对比增强放疗，适用于第一次临床试验的脑转移瘤的均匀碘吸收。(C)2010年美国医学物理学家协会。[DOI：10.1118/1.3327455]
Purpose: Synchrotron stereotactic radiotherapy (SSRT) is a treatment that involves the targeting of high-Z elements into tumors followed by stereotactic irradiation with monochromatic x-rays from a synchrotron source, tuned at an optimal energy. The irradiation geometry, as well as the secondary particles generated at a higher yield by the medium energy x-rays on the high-Z atoms (characteristic x-rays, photoelectrons, and Auger electrons), produces a localized dose enhancement in the tumor. Iodine-enhanced SSRT with systemic injections of iodinated contrast agents has been successfully developed in the past six years in the team, and is currently being transferred to clinical trials. The purpose of this work is to study the impact on the SSRT treatment of the contrast agent type, the beam quality, the irradiation geometry, and the beam weighting for defining an optimized SSRT treatment plan.Methods: Theoretical dosimetry was performed using the MCNPX particle transport code. The simulated geometry was an idealized phantom representing a human head. A virtual target was positioned in the central part of the phantom or off-centered by 4 cm. The authors investigated the dosimetric characteristics of SSRT for various contrast agents: Iodine, gadolinium, and gold; and for different beam qualities: Monochromatic x-ray beams from a synchrotron source (30-120 keV), polychromatic x-ray beams from an x-ray tube (80, 120, and 180 kVp), and a 6 MV x-ray beam from a linear accelerator. Three irradiation geometries were studied: One arc or three noncoplanar arcs dynamic arc therapy, and an irradiation with a finite number of beams. The resulting dose enhancements, beam profiles, and histograms dose volumes were compared for iodine-enhanced SSRT. An attempt to optimize the irradiation scheme by weighing the finite x-ray beams was performed. Finally, the optimization was studied on patient specific 3D CT data after contrast agent infusion.Results: It was demonstrated in this study that an 80 keV beam energy was a good compromise for treating human brain tumors with iodine-enhanced SSRT, resulting in a still high dose enhancement factor (about 2) and a superior bone sparing in comparison with lower energy x-rays. This beam could easily be produced at the European Synchrotron Radiation Facility medical beamline. Moreover, there was a significant diminution of dose delivered to the bone when using monochromatic x-rays rather than polychromatic x-rays from a conventional tube. The data showed that iodine SSRT exhibits a superior sparing of brain healthy tissue in comparison to high energy treatment. The beam weighting optimization significantly improved the treatment plans for off-centered tumors, when compared to nonweighted irradiations.Conclusions: This study demonstrated the feasibility of realistic clinical plans for low energy monochromatic x-rays contrast-enhanced radiotherapy, suitable for the first clinical trials on brain metastasis with a homogeneous iodine uptake. (C) 2010 American Association of Physicists in Medicine. [DOI: 10.1118/1.3327455]