Improving quantitative accuracy and tissue visualization in CBCT guided radiation therapy

项目总结 尽管锥束计算机断层扫描(CBCT)是最常用的体积成像 作为一种指导方式，其在治疗监测和针对患者的背景下的作用受到严重限制 放射治疗中的治疗改进。由于CBCT的图像质量较差，临床医生无法明确 可视化软组织以评估解剖变化，从而影响其临床决策。此外， 用于治疗监测的工具，如可变形配准和剂量计算，不能很好地发挥作用 与今天的CBCT图像相比，由于缺乏CT数字的准确性。 散射辐射仍然是提高CBCT图像质量的根本问题。因此，在 在本项目中，我们提出了二维反散射网格(2D Grid)作为一种新的解决散射问题的方法 问题，并获得适合治疗监测的高质量CBCT图像。我们的设备有 与现有的CBCT防散射栅格相比，它的架构和制造方式有了根本的不同。由于其 优化的网格结构，我们的2D网格提供更高的初级透过率和更好的散射抑制 比当今最先进的防散射栅格性能更好。由于其良好的一次传输和 散射抑制性能，我们的2D网格提高了对比度噪声比和CT数字精度，以 用现有的反散射网格无法达到的水平。 我们假设我们的2D网格将提供显著更好的软组织可视化和CT数值 精确度和可变形配准算法的性能预计会有明显的提高。测试我们的 假设，我们将开发和优化CBCT中2D网格实施的数据处理方法(AIM 1)。随后，我们将制作2D网格原型，并评估其在临床CBCT中的性能 光子和质子治疗系统(目标2)。在基于幻影的评估之后，我们将进行 前瞻性临床试验，以评估改善图像质量的临床应用(目标3)。我们将表演 观察者研究以量化软组织可视化相对于现有临床CBCT的改善 和黄金标准螺旋CT，评估可变形图像配准精度的提高 算法，并对改进后的图像强度和纹理特征的一致性进行了评估。 虽然我们的应用集中在放射治疗上，但2D网格可以在其他CBCT中发挥关键作用 应用领域，如介入放射学、肢体成像和术中成像。由于其 改进的低对比度可视化性能，我们的2D网格还可以减少 CBCT。

PROJECT SUMMARY Even though cone beam computed tomography (CBCT) is the most commonly used volumetric image guidance modality, its role has been severely limited in the context of treatment monitoring and patient-specific treatment modifications in radiation therapy. Due to CBCT’s poor image quality, clinicians cannot clearly visualize soft tissues to assess anatomical changes, thus affecting their clinical decision-making. Moreover, tools for treatment monitoring, such as deformable registration and dose calculation, do not function robustly with today’s CBCT images due to the lack of CT number accuracy. Scattered radiation remains to be the fundamental problem in improving CBCT image quality. Thus, in this project, we propose the two-dimensional antiscatter grid (2D Grid) as a novel device to address the scatter problem and achieve high-quality CBCT images that are suitable for treatment monitoring. Our device has fundamentally different architecture and fabrication than existing antiscatter grids for CBCT. Due to its optimized grid structure, our 2D Grid provides both higher primary transmission and better scatter rejection performance than today’s state-of-the-art antiscatter grids. Due to its favorable primary transmission and scatter rejection performance, our 2D Grid improves the contrast-to-noise ratio and CT number accuracy to levels not achievable with existing antiscatter grids. We hypothesize that our 2D Grid will provide significantly better soft tissue visualization and CT number accuracy, and deformable registration algorithms are expected to perform significantly better. To test our hypotheses, we will develop and optimize data processing methods for 2D Grid implementation in CBCT (Aim 1). Subsequently, we will fabricate 2D Grid prototypes and evaluate their performance in clinical CBCT systems for photon and proton therapy (Aim 2). Following phantom based evaluations, we will conduct a prospective clinical trial to evaluate the clinical utility of improved image quality (Aim 3). We will perform observer studies to quantify the improvement in soft tissue visualization with respect to existing clinical CBCT and gold-standard Helical CT, assess the improvement in accuracy of deformable image registration algorithms, and evaluate the improvement in consistency of image intensity and texture features. While our application is focused on radiation therapy, the 2D Grid can play a key role in other CBCT applications, such as interventional radiology, extremity imaging, and intraoperative imaging. Due to its improved low-contrast visualization performance, our 2D Grid may also allow reduction of the imaging dose in CBCT.