Ma Yiqun, Gang Grace J, Ehtiati Tina, Reynolds Tess, Russ Tom, Wang Wenying, Weiss Clifford, Theodore Nicholas, Hong Kelvin, Siewerdsen Jeffrey, Stayman J Webster
Johns Hopkins University, Baltimore, MD, USA.
Siemens Healthineers.
Proc SPIE Int Soc Opt Eng. 2022 Feb-Mar;12034. doi: 10.1117/12.2612448. Epub 2022 Apr 4.
Metal artifacts have been a difficult challenge for cone-beam CT (CBCT), especially for intraoperative imaging. Metal surgical tools and implants are often present in the field of view and can attenuate X-rays so heavily that they essentially create a missing-data problem. Recently, an increasing number of intra-operative imaging systems such as robotic C-arms are capable of non-circular orbits for data acquisition. Such trajectories can potentially improve sampling and the degree of data completeness to solve the metal-induced missing-data problem, thereby reducing or eliminating the associated image artifacts. In this work, we extend our prior theoretical and experimental work and implement non-circular orbits for metal artifact reduction on a clinical robotic C-arm (Siemens Artis zeego). To maximize the potential for clinical translation, we restrict our implementation to standard built-in motion and data collection functions, also available on other zeego systems, and work within the physical constraints and limitations on positioning and motion. Customized software tools for data extraction, processing, calibration, and reconstruction are used. We demonstrate example non-circular orbits and the resulting image quality using a phantom containing pedicle screws for spine fixation. As compared with a standard circular CBCT orbit, these non-circular orbits exhibit significantly reduced metal artifacts. These results suggest a high potential for image quality improvements for intraoperative CBCT imaging when metal tools or implants are present in the field-of-view.
金属伪影一直是锥束CT（CBCT）面临的一个难题，尤其是在术中成像方面。金属手术工具和植入物常常出现在视野范围内，它们对X射线的衰减非常严重，以至于基本上造成了数据缺失问题。最近，越来越多的术中成像系统，如机器人C型臂，能够采用非圆形轨道进行数据采集。这样的轨迹有可能改善采样和数据完整性程度，以解决金属导致的数据缺失问题，从而减少或消除相关的图像伪影。在这项工作中，我们扩展了之前的理论和实验工作，并在临床机器人C型臂（西门子Artis zeego）上实现了用于减少金属伪影的非圆形轨道。为了最大限度地提高临床转化的潜力，我们将实现过程限制在标准的内置运动和数据采集功能上，其他zeego系统也具备这些功能，并且在定位和运动的物理约束和限制范围内开展工作。我们使用了定制的软件工具进行数据提取、处理、校准和重建。我们展示了使用包含用于脊柱固定的椎弓根螺钉的体模的示例非圆形轨道及其产生的图像质量。与标准的圆形CBCT轨道相比，这些非圆形轨道的金属伪影显著减少。这些结果表明，当视野中存在金属工具或植入物时，术中CBCT成像的图像质量有很大的提升潜力。
