Quantitative dual-energy CT imaging for radiation therapy treatment planning

描述（申请人提供）：定量双能CT成像用于放射治疗治疗计划质子束治疗（PT）和低能量（20-60 keV）光子发射近距离放射治疗（LEPBT）是一种快速发展的治疗方式，具有很大的潜力，可以改善放射治疗的临床结果，因为它们能够在不影响周围正常组织的情况下向目标组织输送高剂量。两种方式的剂量传递对受照射组织的原子组成和选择密度都很敏感。对于LEPBT，目前的剂量计算实践忽略了组织的不均匀性，导致剂量预测误差高达2倍。对于PT，目前的定量单能量计算机断层扫描成像（QSECT）导致3-6毫米范围的不确定性，这显著增加了邻近器官暴露于高剂量。推荐的散装组织成分是基于不充分的数据，患者之间和患者内部的差异很大，基本上是未知的，不能为临床治疗计划或评估PT或LEPBT的剂量递送不确定性提供充分的基础。由于组织组成和电子密度的独立变化，传统的QSECT不足以定量研究PT和LEPBT的放射组织特性。该项目的目标是开发和验证一种新的定量双能CT （QDECT）成像技术，该技术能够准确地成像放射学特性，并通过评估小患者样本中组织不均匀性的大小和临床意义来证明QDECT的实用性。为实现这些目标，提出了三个具体目标。在具体目标1中，将开发一种新的统计图像重建算法，用于重建从临床多层CT成像系统导出的双能量螺旋图导出的三维截面图。具体来说，一个交替最小化正则化的3D重建引擎将被适应和优化，以解决近距离治疗和质子束剂量计划的准确组织图成像问题，并实现临床原型。在具体目标2中，从实验获得的双能量图重建的QDECT横截面图像将针对实验幻像、患者数据和计算基准进行验证。对估计误差的分析将用于上述调幅重构算法优化工作的重点。开发的QDECT过程将用于研究质子停止功率和光子截面图在我们的小患者群体中的大小和可变性。Specific Aim 3将使用现有的治疗计划系统和蒙特卡洛剂量估计代码，研究更准确的患者特异性QDECT横截面分布对头颈部、前列腺、乳腺癌和肺癌部位的模拟近距离治疗、电子束和质子束治疗计划的剂量学和临床影响。

DESCRIPTION (provided by applicant): Quantitative dual-energy CT imaging for radiation therapy treatment planning 6. Project Summary/Abstract Proton-beam therapy (PT) and low-energy (20-60 keV) photon-emitting brachytherapy (LEPBT) are rapidly evolving modalities with high potential for improving radiation therapy clinical outcomes because of their ability to deliver high doses to the target tissue while sparing surrounding normal tissues. Dose delivery from both modalities is sensitive to the atomic composition as well as election density of the irradiated tissues. For LEPBT, current dose-calculation practice ignores tissue inhomogeneity, introducing dose-prediction errors as large as a factor of 2. For PT, current quantitative single-energy computed tomography imaging (QSECT) leads to 3-6 mm range uncertainties that significantly increases exposure of adjacent organs to high doses. Recommended bulk tissue compositions are based upon inadequate data with large and essentially unknown patient-to-patient and intrapatient variability and cannot provide an adequate basis either for clinical treatment planning or assessing dose delivery uncertainty in PT or LEPBT. Conventional QSECT is inadequate for quantitative study of PT and LEPBT radiological tissue properties because tissue composition and electron density vary independently. The goal of this project is to develop and validate a novel quantitative dual-energy CT (QDECT) imaging technology able to accurately image the radiological properties and to demonstrate QDECT utility by assessing the magnitude and clinical significance of tissue inhomogeneities in a small patient sample. To achieve these goals, three specific aims are proposed. In Specific Aim 1, a novel statistical image reconstruction algorithm will be developed for reconstructing 3D cross-section maps derived from dual energy spiral sinograms exported from a clinical multi-slice CT imaging system. Specifically, an alternating minimization regularized, 3D reconstruction engine will be adapted and optimized to the problems of accurate tissue-map imaging for brachytherapy and proton-beam dose planning and a clinical prototype implemented. In Specific Aim 2, QDECT cross-section images reconstructed from experimentally-acquired dual-energy sinograms will be validated against experimental phantom, patient data, and computational benchmarks. Analysis of estimation errors will be used to focus AM reconstruction algorithm optimization efforts above. The developed QDECT process will be used to study the magnitude and variability of proton stopping-power and photon-cross section maps in our small patient population. Specific Aim 3 will study the dosimetric and clinical impact of more accurate patient-specific QDECT cross-section distributions on simulated brachytherapy, electron-beam and proton-beam treatment plans in head and neck, prostate, breast, and lung cancer sites using available treatment-planning systems and Monte Carlo dose-estimation codes.