Ludwig-Maximilian University, Munich, Germany. Heidelberg Ion-Beam Therapy Center, Heidelberg, Germany.
Phys Med Biol. 2014 Jan 6;59(1):1-21. doi: 10.1088/0031-9155/59/1/1. Epub 2013 Dec 10.
Since the interest in ion-irradiation for tumour therapy has significantly increased over the last few decades, intensive investigations are performed to improve the accuracy of this form of patient treatment. One major goal is the development of methods for in vivo dose verification. In proton therapy, a PET (positron emission tomography)-based approach measuring the irradiation-induced tissue activation inside the patient has been already clinically implemented. The acquired PET images can be compared to an expectation, derived under the assumption of a correct treatment application, to validate the particle range and the lateral field position in vivo. In the context of this work, TPSPET is introduced as a new approach to predict proton-irradiation induced three-dimensional positron emitter distributions by means of the same algorithms of the clinical treatment planning system (TPS). In order to perform additional activity calculations, reaction-channel-dependent input positron emitter depth distributions are necessary, which are determined from the application of a modified filtering approach to the TPS reference depth dose profiles in water. This paper presents the implementation of TPSPET on the basis of the research treatment planning software treatment planning for particles. The results are validated in phantom and patient studies against Monte Carlo simulations, and compared to β(+)-emitter distributions obtained from a slightly modified version of the originally proposed one-dimensional filtering approach applied to three-dimensional dose distributions. In contrast to previously introduced methods, TPSPET provides a faster implementation, the results show no sensitivity to lateral field extension and the predicted β(+)-emitter densities are fully consistent to the planned treatment dose as they are calculated by the same pencil beam algorithms. These findings suggest a large potential of the application of TPSPET for in vivo dose verification in the daily clinical routine.
由于过去几十年来人们对离子辐射肿瘤治疗的兴趣显著增加，因此正在进行密集的研究，以提高这种患者治疗形式的准确性。一个主要目标是开发用于体内剂量验证的方法。在质子治疗中，已经临床实施了一种基于 PET（正电子发射断层扫描）的方法，该方法测量患者体内照射引起的组织激活。获得的 PET 图像可以与假设治疗应用正确的情况下得出的预期进行比较，以验证体内粒子射程和横向场位置。在这项工作的背景下，引入了 TPSPET 作为一种新方法，通过临床治疗计划系统（TPS）的相同算法来预测质子辐照引起的三维正电子发射体分布。为了进行额外的活性计算，需要依赖反应通道的输入正电子发射体深度分布，这是通过将改进的滤波方法应用于水中 TPS 参考深度剂量分布来确定的。本文介绍了在粒子治疗研究治疗计划软件的基础上实现 TPSPET。将结果与蒙特卡罗模拟进行了体模和患者研究的验证，并与从应用于三维剂量分布的略有修改的一维滤波方法获得的β(+)发射体分布进行了比较。与以前介绍的方法相比，TPSPET 提供了更快的实现方式，结果对横向场扩展不敏感，并且预测的β(+)发射体密度与计划的治疗剂量完全一致，因为它们是通过相同的铅笔束算法计算的。这些发现表明，在日常临床实践中，TPSPET 具有很大的应用潜力，可用于体内剂量验证。
