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

描述(申请人提供)：本研究计划提出一种同步移动网格(SOGG)系统，以改善千伏锥束计算机断层扫描(KVCBCT)的图像质量。与传统的扇束计算机层析成像(CT)相比，CBCT具有一次旋转采集多层图像的能力，以及使用平板探测器(FPD)获得的空间分辨率和方便性。基于FPD的CBCT在IGRT中的引入显著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在影像引导的外科手术和介入治疗中也有潜在的重要应用，以及在诊断放射学中对运动器官的快速成像。然而，散射、图像滞后和门架弯曲这三个主要问题严重降低了CBCT的图像质量，从而阻碍了其进一步的应用。为了减小散射效应，人们提出了许多方法。这些方法可分为两类：(1)直接消散和(2)散射校正。然而，目前的直接散射抑制方法的效率往往是有限的，虽然散射校正方法可以减少散射伪影，但它们通常会进一步降低对比度噪声比。由于当前问题的复杂性，为减少滞后和弹性效应而提出的各种方法也只显示出有限的改善。雾霾系统旨在解决这些迄今尚未解决的问题。它在一次扫描期间在每个龙门位置进行多个部分投影，栅格以与龙门运动同步的振荡模式快速移动。通过合并同一门架位置上的所有部分投影来获得完整投影。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灵活问题，允许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，烟雾系统包括一个软件平台，该平台由基于蒙特卡洛(MC)的模拟和进一步优化图像质量的压缩传感算法组成。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--如CNR的增加和散布伪影的去除--已经实现。仿真研究还表明，利用被SEPTA遮挡的相邻阴影区域中的滞后可以校正图像区域中的滞后。我们还证明了网格可以用来直接检测扫描中的龙门摆动分布。烟雾系统将在CBCT试验台上开发和测试，然后转移到临床CBCT系统进行临床验证。 公共卫生相关性：本研究提出了一种同步移动网格(SOGG)系统来解决当前临床锥束计算机断层扫描(CBCT)中的三个主要问题：散射、图像滞后和门架弯曲。烟雾系统将极大地改善第二代自适应放射治疗CBCT扫描仪的图像质量。我们将建立一个原型系统，并在临床环境中进行测试。

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. PUBLIC HEALTH RELEVANCE: This study proposes a synchronized moving grid (SMOG) system to solve scatter, image lag and gantry flex, the three major problems in current clinical cone beam computed tomography (CBCT) with a same device. The SMOG system will vastly improve the image quality toward the second generation CBCT scanner for adaptive radiotherapy. We will build a prototype system and test it in the clinical setting.