Fotouhi Javad, Fuerst Bernhard, Wein Wolfgang, Navab Nassir
Computer Aided Medical Procedures, Johns Hopkins University, Baltimore, MD, USA.
ImFusion GmbH, Munich, Germany.
Int J Comput Assist Radiol Surg. 2017 Jul;12(7):1211-1219. doi: 10.1007/s11548-017-1572-y. Epub 2017 Mar 25.
Cone-Beam Computed Tomography (CBCT) is an important 3D imaging technology for orthopedic, trauma, radiotherapy guidance, angiography, and dental applications. The major limitation of CBCT is the poor image quality due to scattered radiation, truncation, and patient movement. In this work, we propose to incorporate information from a co-registered Red-Green-Blue-Depth (RGBD) sensor attached near the detector plane of the C-arm to improve the reconstruction quality, as well as correcting for undesired rigid patient movement.
Calibration of the RGBD and C-arm imaging devices is performed in two steps: (i) calibration of the RGBD sensor and the X-ray source using a multimodal checkerboard pattern, and (ii) calibration of the RGBD surface reconstruction to the CBCT volume. The patient surface is acquired during the CBCT scan and then used as prior information for the reconstruction using Maximum-Likelihood Expectation-Maximization. An RGBD-based simultaneous localization and mapping method is utilized to estimate the rigid patient movement during scanning.
Performance is quantified and demonstrated using artificial data and bone phantoms with and without metal implants. Finally, we present movement-corrected CBCT reconstructions based on RGBD data on an animal specimen, where the average voxel intensity difference reduces from 0.157 without correction to 0.022 with correction.
This work investigated the advantages of a C-arm X-ray imaging system used with an attached RGBD sensor. The experiments show the benefits of the opto/X-ray imaging system in: (i) improving the quality of reconstruction by incorporating the surface information of the patient, reducing the streak artifacts as well as the number of required projections, and (ii) recovering the scanning trajectory for the reconstruction in the presence of undesired patient rigid movement.
锥形束计算机断层扫描（CBCT）是一种用于骨科、创伤、放射治疗引导、血管造影和牙科应用的重要三维成像技术。CBCT的主要局限性在于由于散射辐射、截断和患者移动导致图像质量较差。在这项工作中，我们建议整合来自安装在C形臂探测器平面附近的共注册红-绿-蓝-深度（RGBD）传感器的信息，以提高重建质量，并校正不必要的患者刚性移动。
RGBD和C形臂成像设备的校准分两步进行：（i）使用多模态棋盘格图案对RGBD传感器和X射线源进行校准，以及（ii）将RGBD表面重建校准到CBCT体积。在CBCT扫描期间获取患者表面，然后将其用作使用最大似然期望最大化进行重建的先验信息。利用基于RGBD的同时定位和映射方法来估计扫描期间患者的刚性移动。
使用有和没有金属植入物的人工数据和骨模型对性能进行了量化和展示。最后，我们展示了基于动物标本上RGBD数据的运动校正CBCT重建，其中平均体素强度差异从未校正时的0.157降低到校正后的0.022。
这项工作研究了配备RGBD传感器的C形臂X射线成像系统的优势。实验表明了光/ X射线成像系统在以下方面的益处：（i）通过整合患者的表面信息提高重建质量，减少条纹伪影以及所需投影的数量，以及（ii）在存在不期望的患者刚性移动的情况下恢复用于重建的扫描轨迹。
