Four-dimensional Adaptive Thoracic Radiotherapy

最近的临床数据表明，两种常规治疗的剂量-肿瘤反应关系明确。 非小细胞肺癌的放射治疗，几项大型研究证实， 肺、食管、心脏和支气管的剂量-毒性关系。然而，肺肿瘤随着 呼吸，每天改变骨骼解剖结构的位置， 在放疗过程中的体积。这些解剖学变化阻碍了准确的成像、计划 和胸部放射治疗的输送，因此，阻碍了我们最大限度地提高治疗窗口的能力， 局部控制/生存率和治疗引起的并发症之间的关系。 呼吸门控、屏气放射治疗和四维放射治疗的进展 然而，考虑到一些呼吸运动问题，这些技术已经引入了额外的 这些问题还有待解决。例如，4D CT采集中的呼吸不规则性 过程表现为图像伪影，随后表现为整个过程中的系统误差。 疗程解剖结构运动和呼吸信号之间的时间变化被用作 该运动的替代引入了显著的误差，因为替代和 解剖结构运动是位置相关的，并且解剖结构和替代运动随循环而变化， 今天的一天 该项目的总体目标是系统地量化整个过程中的解剖变异， 针对代表性患者队列的放射治疗，制定策略以减轻变化的影响， 从而使其临床影响最小化，同时严格考虑剩余的不确定性。到 实现目标的具体目标是： (1)进行临床影像学研究，以量化内部和外部肿瘤的大小和分布， 分次内解剖学变化，包括肿瘤/呼吸信号相关性的时间稳定性。 (2)通过（a）改进4D CT数据，改善4D CT图像的采集和重建 收集过程和（B）使用不同的呼吸输入评估4D CT图像重建， 除了量化可变形图像配准算法的不确定性之外， 4D IGART。 (3)开发和研究基于概率的分次间和分次内4D IGART的功效 临床应用的策略，并进行模拟研究，以确定剂量和生物 4D IGART系统的改进增益。 该项目的高潮是4D IGART安全性和有效性研究的临床实施。

Recent clinical data demonstrates a clear dose-tumor response relationship for both conventional fractionation and hypofractionated nonsmall-cell lung cancer radiotherapy; several large studies confirm the dose-toxicity relationship for lung, esophagus, heart and bronchus. However, lung tumors move with respiration, change position with respect to skeletal anatomy from day to day, and generally decrease in volume during a course of radiotherapy. These anatomic changes hinder the accurate imaging, planning and delivery of thoracic radiotherapy and, hence, impede our ability to maximize the therapeutic window between local control/survival and treatment-induced complications. Developments in respiratory gating, breath-hold radiotherapy and four-dimensional (4D) radiotherapy account for some of the respiratory motion issues, however, these techniques have introduced additional problems that have yet to be addressed. For example, respiratory irregularities in the 4D CT acquisition process manifest themselves as image artifacts and subsequently as systematic errors throughout the entire treatment course. Temporal variations between anatomy motion and the respiratory signal used as a surrogate for this motion introduce significant errors, since the correlation between the surrogate and anatomy motion is location-dependent, and anatomy and surrogate motions vary from cycle to cycle and day today. The overall goal of the project is to systematically quantify anatomic variations throughout a course of radiotherapy for a representative patient cohort, develop strategies to mitigate the effect of the variations, and, thereby, minimize their clinical impact whilst rigorously accounting for the residual uncertainties. To achieve the goal the specific aimsare: (1) To conduct a clinical imaging study to quantify the magnitude and distribution of inter- and intrafraction anatomic variations, including the temporal stability of the tumor/respiration signal correlation. (2) To improve the acquisition and reconstruction of 4D CT images by (a) advancing the 4D CT data collection process and (b) evaluating 4D CT image reconstruction using different respiratory inputs, in addition to quantifying the uncertainty of deformable image-registration algorithms, a core tool for 4D IGART. (3) To develop and investigate the efficacy of inter- and intrafraction probabilistic-based 4D IGART strategies for clinical application and to perform simulation studies to determine the dosimetric and biological improvement gains from the 4D IGART system. The culmination of the project is the clinical implementation of 4D IGART safety and efficacy studies.