One-dimensional linear X-ray grids are typically used in clinical practice to reduce the number of scattered X-rays reaching the detector surface, thus improving image contrast in radiography. However, such grids can only remove scattered X-rays in one direction. Additionally, the primary challenge in using X-ray grids in digital radiography is the presence of grid artifacts, such as grid strip shadows and moiré, which can reduce image quality. To overcome these difficulties, in this study, we developed a prototype two-dimensional (2D) crisscrossed grid with a strip density of 1.724 lines/mm by adopting a high-precision sawing process to further improve its scatter radiation removal ability and implemented it in a cone-beam computed tomography (CBCT) system to enhance image quality. We propose a new software-based method called the grid artifact reduction (GAR) algorithm to efficiently eliminate grid artifacts of a 2D grid in CBCT. The GAR algorithm involves three main steps: 1) preprocessing for flat-field compensation, 2) postprocessing for GAR, and 3) CBCT reconstruction. To verify the efficacy of the proposed approach, we conducted an experiment on a CT quality control phantom (Pro-CT MK II™) and quantitatively evaluated the CBCT image quality using the contrast-to-noise ratio (CNR) and Hounsfield unit (HU) accuracy error. The CNR value measured in the CBCT image obtained using the 2D grid and proposed GAR algorithm was 3.22, which is approximately 4.4 times of the value obtained without GAR. Furthermore, the corresponding HU accuracy error was 30.47, an improvement of approximately 1.3 times. These results indicate that the proposed approach is highly efficient in eliminating scattered X-rays, thereby improving the quality of CBCT images. Consequently, high-quality CBCT images were obtained using the proposed approach (i.e., using a 2D crisscrossed grid in CBCT and the proposed GAR algorithm).

中文翻译：

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从锥形束计算机断层扫描中的二维纵横交错网格中去除网格伪影以提高图像质量

一维线性 X 射线网格通常用于临床实践，以减少到达探测器表面的散射 X 射线数量，从而提高射线照相中的图像对比度。然而，这种网格只能去除一个方向上的散射X射线。此外，在数字射线照相中使用 X 射线网格的主要挑战是网格伪影的存在，例如网格条阴影和莫尔条纹，这会降低图像质量。为了克服这些困难，在本研究中，我们通过采用高精度锯切工艺，开发了条带密度为1.724线/毫米的二维（2D）纵横交错网格原型，进一步提高了其散射辐射去除能力，并在用于提高图像质量的锥形束计算机断层扫描 (CBCT) 系统。我们提出了一种新的基于软件的方法，称为网格伪影减少（GAR）算法，以有效消除 CBCT 中二维网格的网格伪影。 GAR 算法涉及三个主要步骤：1）平场补偿预处理，2）GAR 后处理，3）CBCT 重建。为了验证所提出方法的有效性，我们在 CT 质量控制体模 (Pro-CT MK II™) 上进行了实验，并使用对比噪声比 (CNR) 和亨斯菲尔德单位 (HU) 定量评估了 CBCT 图像质量。 ) 精度误差。使用二维网格和提出的 GAR 算法获得的 CBCT 图像中测得的 CNR 值为 3.22，大约是没有使用 GAR 时获得的值的 4.4 倍。此外，相应的HU精度误差为30.47，提高了约1.3倍。这些结果表明，该方法在消除散射 X 射线方面非常有效，从而提高了 CBCT 图像的质量。因此，使用所提出的方法（即在 CBCT 中使用二维纵横交错的网格和所提出的 GAR 算法）获得了高质量的 CBCT 图像。