The rotate-plus-shift C-arm trajectory. Part I. Complete data with less than 180° rotation
The rotate-plus-shift C-arm trajectory. Part I. Complete data with less than 180° rotation
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DOI：
10.1118/1.4944785
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发表时间：
2016-05-01
期刊：
影响因子：
3.8
通讯作者：
Kachelriess, Marc
中科院分区：
文献类型：
--
作者：
Ritschl, Ludwig;Kuntz, Jan;Kachelriess, Marc
目的：近十年来，基于C臂的锥束CT成为一种广泛使用的术中成像方式。通常，C臂CT扫描是使用围绕感兴趣区域的圆形或椭圆轨迹进行的。因此，必须覆盖至少180度加风扇角度的角度范围，以确保完全采样的数据集。然而，专注于经典2D应用(如透视)的移动C形臂可能会被限制在低于180度的机械旋转范围内，以提高操控性和可用性。本文提出的方法允许使用新的轨迹设计，在被限制在至少180度减去风扇角度的机械旋转范围的系统中获取全采样数据集。这使得与CT类似的3D成像可以与主要用于2D成像的C型臂设备一起使用。方法：所提出的轨迹通过增加两个线性位移来扩展C型臂系统的机械旋转范围。由于扇束几何结构的发散特性，这两个漂移导致额外的角度范围为扇角的一半。将扫描开始时的一个移位与随后的旋转和第二个移位相结合，得到的旋转加移位轨迹能够仅使用180度减去风扇旋转角度来获取完全采样的数据集。例如，可以使用全机动C形臂系统的两个正交定位轴来执行移位。使用两个原型C形臂系统在体模和身体检查中对该轨迹进行了评估。结果：提出的轨迹可实现无限角伪影的重建。与180度减去扇角的有限角度重建相比，图像质量显著提高。旋转+平移重建的细节被清晰地描绘出来，而在有限角度扫描中，它们被伪影所主导。结论：本文提出的方法使用旋转范围小于180度的C形臂进行3D成像，为C形臂装置增加了完整的3D功能，同时保持了2D成像的舒适性和可用性。这种方法具有明显的临床应用潜力，特别是对术中3D成像日益增长的需求。(C)2016年美国医学物理学家协会。
Purpose: In the last decade, C-arm-based cone-beam CT became a widely used modality for intraoperative imaging. Typically a C-arm CT scan is performed using a circular or elliptical trajectory around a region of interest. Therefore, an angular range of at least 180 degrees plus fan angle must be covered to ensure a completely sampled data set. However, mobile C-arms designed with a focus on classical 2D applications like fluoroscopy may be limited to a mechanical rotation range of less than 180 degrees to improve handling and usability. The method proposed in this paper allows for the acquisition of a fully sampled data set with a system limited to a mechanical rotation range of at least 180 degrees minus fan angle using a new trajectory design. This enables CT like 3D imaging with a wide range of C-arm devices which are mainly designed for 2D imaging.Methods: The proposed trajectory extends the mechanical rotation range of the C-arm system with two additional linear shifts. Due to the divergent character of the fan-beam geometry, these two shifts lead to an additional angular range of half of the fan angle. Combining one shift at the beginning of the scan followed by a rotation and a second shift, the resulting rotate-plus-shift trajectory enables the acquisition of a completely sampled data set using only 180 degrees minus fan angle of rotation. The shifts can be performed using, e.g., the two orthogonal positioning axes of a fully motorized C-arm system. The trajectory was evaluated in phantom and cadaver examinations using two prototype C-arm systems.Results: The proposed trajectory leads to reconstructions without limited angle artifacts. Compared to the limited angle reconstructions of 180 degrees minus fan angle, image quality increased dramatically. Details in the rotate-plus-shift reconstructions were clearly depicted, whereas they are dominated by artifacts in the limited angle scan.Conclusions: The method proposed here employs 3D imaging using C-arms with less than 180 degrees rotation range adding full 3D functionality to a C-arm device retaining both handling comfort and the usability of 2D imaging. This method has a clear potential for clinical use especially to meet the increasing demand for an intraoperative 3D imaging. (C) 2016 American Association of Physicists in Medicine.