Markerless Motion Tracking of Lung Tumors using Dual Energy Imaging

项目总结/摘要 肺癌是世界上最常见和最致命的恶性肿瘤之一。放射治疗（RT） 通常单独使用或与手术或化疗联合使用，因此是治疗中的关键组分。 管理这种疾病。然而，肺中RT的准确递送受到呼吸运动的限制， 可导致肿瘤的显著移位（高达2 cm）。如果没有补偿，这项动议就需要 照射更大体积的正常肺以解释肿瘤的移位。这种更大的体积 肺照射增加了有症状的放射性肺炎的发生率。已经有许多方法 临床上用于减少照射的肺体积，包括使用屏气和按压。 然而，对于经常患有多种合并症的患者来说，两者都是不舒服和困难的。可选择地， 研究人员正在评估真实的跟踪肿瘤的方法，并可能调整治疗参数 肺部肿瘤的位置实现这一目标的方法需要植入基准标记或 电磁应答器然而，这些装置的植入具有气胸的显著风险， 肺出血和基础慢性阻塞性肺疾病（COPD）恶化。另一 肿瘤跟踪的方法-无标记肿瘤跟踪（MTT）-依赖于在肿瘤发生时获得的肿瘤图像。 治疗时间。用于递送RT的最常见模态是配备有加速器的线性加速器。 机载成像仪（OBI）。基于X射线的MTT在标准直线加速器上使用平面MV或kV成像， 因为它使用广泛可用的技术并且可以在接近真实的时间内执行。的情况下 肿瘤清晰可见，基于X射线的MTT可以以高度准确性追踪肿瘤。然而一个主要 MTT的困难在于肿瘤重叠骨在X射线投影上可能检测不到。 我们的小组已经探索了双能量（DE）荧光成像，以增加成功的可能性， 准确的MTT，并已实现DE成像的OBI的商业直线加速器使用快速kV 交换技术DE成像涉及在高（即，120 kVp）和低（即，60 kVp） 能量通过执行加权对数减法（WLS），产生第三图像，其抑制了 骨和增强软组织/肿瘤的可见性。我们的假设是，在线性上实施DE成像 加速器将实现用于增强肿瘤可视化和成像的实用且成本有效的方法 此外，DE成像将允许MTT确保高剂量递送到肿瘤 同时限制照射的正常组织的体积。为了验证这一假设，并实现这一目标， A）确定快速kV DE成像的改进领域， MTT的目标是临床实施和B）制定质量保证计划和临床 验证。

Project Summary/Abstract Lung cancer is one of the most common and deadliest malignancies in the world. Radiation therapy (RT) is often used alone or in combination with surgery or chemotherapy, and thus is a critical component in the management of this disease. However, accurate delivery of RT in the lung is limited by respiratory motion, which can result in significant displacements of the tumor (up to 2 cm). Without compensation, this motion necessitates the irradiation of a larger volume of normal lung to account for displacement of the tumor. This larger volume of lung irradiated increases the incidence of symptomatic radiation pneumonitis. A number of methods have been used clinically to reduce the volume of lung irradiated including the use of breath hold and compression. However, both are uncomfortable and difficult for patients who often have multiple comorbidities. Alternatively, researchers are evaluating methods to track the tumor in real time and potentially adapt the treatment parameters to the position of the lung tumor. Methods to accomplish this goal require the implantation of fiducial markers or electromagnetic transponders. However, implantation of these devices carries a significant risk of pneumothorax, pulmonary hemorrhage and exacerbation of underlying chronic obstructive pulmonary disease (COPD). Another approach for tumor tracking – markerless tumor tracking (MTT) – relies on images of the tumor obtained at the time of treatment. The most common modality for the delivery of RT is the linear accelerator equipped with an on-board imager (OBI). X-ray-based MTT, using planar MV or kV imaging on a standard linear accelerator, is attractive as it uses a widely available technology and can be performed in near real time. In cases where the tumor is clearly visible, x-ray-based MTT can track tumors with a high degree of accuracy. However, a major difficulty with MTT is that tumor-overlapping bone may not be detectable on x-ray projections. Our group has explored dual energy (DE) fluoroscopic imaging to increase the likelihood of successful and accurate MTT, and have implemented DE imaging on the OBI of a commercial linear accelerator using fast-kV switching technology. DE imaging involves obtaining x-ray images at high (i.e., 120 kVp) and low (i.e., 60 kVp) energies. By performing a weighted-logarithmic subtraction (WLS), a third image is produced that suppresses bone and enhances soft tissue/tumor visibility. Our hypothesis is that implementing DE imaging on a linear accelerator will enable a practical and cost effective method for enhanced tumor visualization and image guidance in lung RT. Moreover, DE imaging will allow for MTT ensuring a high dose is delivered to the tumor while limiting the volume of normal tissue irradiated. To test this hypothesis and to accomplish the goals of this research, the following specific aims are proposed: A) Identify areas for improvement in fast-kV DE imaging and MTT with the goal toward clinical implementation and B) Development of a quality assurance program and clinical validation.