Dynamic PET-DECT for Proton Treatment Verification and Response Assessment

 描述（由申请人提供）：质子治疗（PT）是最先进的放射治疗方式之一。然而，由于高度局部化的剂量沉积，治疗计划中的不确定性具有比光子治疗中高得多的影响。在治疗计划期间，可能会引入高达几厘米的范围不确定性。剂量输送的详细验证将使PT的全部潜力得以实现。治疗期间核碎裂反应产生的放射性分布的PET成像已成为体内治疗验证的唯一实用方法。我们已经使用了一个室内PET扫描仪测量质子照射后的放射性浓度的历史，显示15 O形成超过80%的PET信号后立即照射。因此，我们开发了一种全新的理论，直接从数据中估计同位素特定的生产和清除率。同位素产生是一个基本的终点，因为它是给定质子分布和组织组成的递送剂量的独特函数。15 O的生物清除率可以同时计算，这可能携带有关肿瘤环境的有价值的生理信息。在这个项目中，我们将开发新的方法，质子治疗的室内剂量验证的基础上，15 O生产率地图和双能CT（DECT）。DECT可以提供更准确的组织属性信息，这将改善PET活性分布的Monte Carlo预测，并且还可以潜在地提高治疗计划的准确性。我们建议在幻影中进行控制验证，在动物中进行实验确认，并进行人体试验研究。室内成像将通过新的移动的PET/CT扫描仪得到改善，该扫描仪提供高灵敏度PET和共配准DECT。我们还将评估使用放射敏感性VX 2肿瘤和临床研究中的15 O生物清除率评估肿瘤对治疗反应的可行性，并研究DECT在更准确的质子治疗计划中的价值。

 DESCRIPTION (provided by applicant): Proton therapy (PT) is one of the most advanced modalities of radiation therapy. However, uncertainties in the treatment plan have a much higher impact than in photon therapy due to the highly localized dose deposition. Range uncertainties of up to several centimeters can be introduced during treatment planning. Detailed verification of dose delivery would allow the full potential of PT to be realized. PET imaging of radioactivity distributions produced by nuclear fragmentation reactions during treatments has emerged as the only practical approach for in vivo treatment verification. We have used an in-room PET scanner to measure the radioactivity concentration history after proton irradiation, showing that 15O forms more than 80% of the PET signal immediately after irradiation. Accordingly, we have developed a completely new theory which estimates isotope-specific production and clearance rates directly from the data. The isotope production is a fundamental endpoint since it is a unique function of the dose delivered with a given proton profile and tissue composition. The biological clearance rates of 15O can be calculated concurrently, which may carry valuable physiological information about tumor environment. In this project we will develop new methods for in-room dose verification of proton therapy, based on the 15O production rate maps and Dual Energy CT (DECT). DECT can provide more accurate tissue property information, which will improve the Monte Carlo prediction of PET activity distributions, and also can potentially improve the treatment planning accuracy. We propose controlled validation in phantoms, experimental confirmation in animals, and pilot human studies. In-room imaging will be improved with a new mobile PET/CT scanner offering high sensitivity PET and a co-registered DECT. We will also evaluate the feasibility of assessing tumor responses to treatment using 15O biological clearance rates with radiation-sensitive VX2 tumors and in clinical studies, and investigate the value of DECT in more accurate proton therapy treatment planning.