A synchronized moving grid (SMOG) system to improve CBCT for IGRT and ART

描述（由申请人提供）：本研究计划提出一种同步移动网格（SMOG）系统，以提高千电压锥束计算机断层扫描（kV CBCT）的图像质量。与传统的扇束计算机断层扫描（CT）相比，CBCT的优势在于它能够在一次旋转中获取多个图像切片，并且使用平板探测器（FPD）获得了空间分辨率和便利性。在IGRT中引入基于FPD的CBCT，大大提高了放射治疗的准确性，并可能彻底改变放射治疗程序。CBCT也有潜在的重要应用在图像引导手术和干预，并在诊断放射学快速成像的运动器官。然而，分散、图像滞后和龙门弯曲这三大问题严重降低了CBCT的图像质量，阻碍了其进一步的应用。为了降低散射效应，人们提出了许多方法。这些方法可分为两类：(1)直接散射减少和(2)散射校正。然而，目前直接散射消减方法的效率往往有限，散射校正方法虽然可以减少散射伪影，但通常会进一步降低对比噪声比。由于手头问题的复杂性，提出的各种减少滞后和柔性效应的方法也只显示出有限的改进。雾霾制度旨在解决这些迄今尚未解决的问题。它在扫描期间在每个龙门架位置进行多个部分投影，网格以与龙门架运动同步的振荡模式快速移动。通过合并同一门框位置上的所有部分投影得到一个完整投影。这种方法不仅通过同时减少和校正散射来解决散射问题，而且还有效地解决了滞后和弯曲问题，从而可以在一个简单的设备中同时解决CBCT面临的所有三个主要问题。此外，烟雾系统还包括一个软件平台，该平台由基于蒙特卡罗（MC）的仿真和压缩感知算法组成，可进一步优化图像质量。初步结果证明了这些概念的适用性和前景。对于散射问题，我们使用多次旋转扫描，每次旋转后网格移动一段距离来模拟烟雾系统。图像质量的显著改善——通过增加的CNR和去除散射伪影来证明——已经实现。仿真研究还表明，利用间隔遮挡的相邻阴影区域的滞后可以对图像区域的滞后进行校正。我们还表明，网格可以用来直接检测在扫描中的龙门摆动分布。烟雾系统将在CBCT试验台开发和测试，然后转移到临床CBCT系统进行临床验证。

DESCRIPTION (provided by applicant): This research plan proposes a synchronized-moving-grid (SMOG) system to improve the image quality of kilovoltage cone-beam computed tomography (kV CBCT). CBCT has the advantages over the conventional fan-beam computed tomography (CT) for its ability to acquire multiple slices of images in one rotation, and the spatial resolution and convenience gained by using a flat panel detector (FPD). The introduction of the FPD based CBCT in IGRT has significantly improved the accuracy of radiation treatment and may revolutionize the radiation therapy procedure. CBCT also has potential important applications in image guided surgery and intervention, and in diagnostic radiology for fast imaging of moving organs. However, three major problems-scatter, image lag and gantry flex-significantly degrade the image quality of CBCT, thereby hampering its further applications. Many methods have been proposed to reduce the scatter effect. These methods can be divided into two groups: (1) direct scatter reduction and (2) scatter correction. However, the efficiency o the current direct scatter reduction methods is often limited, and although scatter correction methods can reduce scatter artifacts, they usually further degrade the contrast-to-noise ratio. Various methods proposed to reduce the lag and flex effects have also shown only limited improvements due to the complexity of the issues at hand. The SMOG system aims to address these heretofore unresolved problems. It takes multiple partial- projections at each gantry position during a scan, with the grid moving rapidly in an oscillating pattern synchronized with the gantry motion. A full projection is obtained by merging all partial projections at the same gantry position. This approach not only provides a solution to the scatter problem through simultaneous scatter reduction and correction, it also effectively addresses lag and flex as well, allowing for the simultaneous resolution of all three major problems facing CBCT in one simple device. In addition, the SMOG system includes a software platform comprised of Monte-Carlo (MC)-based simulation and a compressed sensing algorithm that further optimizes the image quality. Preliminary results have demonstrated the applicability and promise of these concepts. For the scatter problem, we used multiple-rotation scans with the grid shifting a distance after each rotation to simulate the SMOG system. Significant improvement in the image quality-as demonstrated by increased CNR and removal of scatter artifacts-has been achieved. A simulation study also shows that the lag in the image region can be corrected by using the lag in the neighboring shadow region blocked by the septa. We have also shown that the grid can be used to directly detect the gantry wobbling distribution in a scan. The SMOG system will be developed and tested in a CBCT test bench, and then transferred to a clinical CBCT system for clinical validation.