Department of Physics, Oakland University, Rochester, Michigan 48309, USA.
Med Phys. 2013 Aug;40(8):081909. doi: 10.1118/1.4812886.
To accelerate iterative algebraic reconstruction algorithms using a cylindrical image grid.
Tetrahedron beam computed tomography (TBCT) is designed to overcome the scatter and detector problems of cone beam computed tomography (CBCT). Iterative algebraic reconstruction algorithms have been shown to mitigate approximate reconstruction artifacts that appear at large cone angles, but clinical implementation is limited by their high computational cost. In this study, a cylindrical voxelization method on a cylindrical grid is developed in order to take advantage of the symmetries of the cylindrical geometry. The cylindrical geometry is a natural fit for the circular scanning trajectory employed in volumetric CT methods such as CBCT and TBCT. This method was implemented in combination with the simultaneous algebraic reconstruction technique (SART). Both two- and three-dimensional numerical phantoms as well as a patient CT image were utilized to generate the projection sets used for reconstruction. The reconstructed images were compared to the original phantoms using a set of three figures of merit (FOM).
The cylindrical voxelization on a cylindrical reconstruction grid was successfully implemented in combination with the SART reconstruction algorithm. The FOM results showed that the cylindrical reconstructions were able to maintain the accuracy of the Cartesian reconstructions. In three dimensions, the cylindrical method provided better accuracy than the Cartesian methods. At the same time, the cylindrical method was able to provide a speedup factor of approximately 40 while also reducing the system matrix storage size by 2 orders of magnitude.
TBCT image reconstruction using a cylindrical image grid was able to provide a significant improvement in the reconstruction time and a more compact system matrix for storage on the hard drive and in memory while maintaining the image quality provided by the Cartesian voxelization on a Cartesian grid.
使用圆柱图像网格加速迭代代数重建算法。
设计四面体束计算机断层扫描 (TBCT) 以克服锥形束计算机断层扫描 (CBCT) 的散射和探测器问题。迭代代数重建算法已被证明可以减轻在大锥角下出现的近似重建伪影，但由于其计算成本高，临床实施受到限制。在这项研究中，开发了一种在圆柱网格上的圆柱体体素化方法，以便利用圆柱几何的对称性。圆柱几何是体积 CT 方法（如 CBCT 和 TBCT）中使用的圆形扫描轨迹的自然匹配。该方法与同时代数重建技术 (SART) 相结合实施。二维和三维数值体模以及患者 CT 图像都用于生成用于重建的投影集。使用一组三个质量指标 (FOM) 将重建图像与原始体模进行比较。
成功地将圆柱体素化与 SART 重建算法结合在圆柱重建网格上实施。FOM 结果表明，圆柱重建能够保持笛卡尔重建的准确性。在三维中，圆柱方法比笛卡尔方法提供了更好的准确性。同时，圆柱方法能够提供大约 40 的加速因子，同时将系统矩阵存储大小减少两个数量级。
使用圆柱图像网格进行 TBCT 图像重建能够显著提高重建时间，并为在硬盘和内存中存储提供更紧凑的系统矩阵，同时保持笛卡尔体素化在笛卡尔网格上提供的图像质量。
