Abstract：
We introduce the Fast Algorithm for Motion Correction (FALCON) software, which allows correction of both rigid and nonlinear motion artifacts in dynamic whole-body (WB) images, irrespective of the PET/CT system or the tracer. Methods: Motion was corrected using affine alignment followed by a diffeomorphic approach to account for nonrigid deformations. In both steps, images were registered using multiscale image alignment. Moreover, the frames suited to successful motion correction were automatically estimated by calculating the initial normalized cross-correlation metric between the reference frame and the other moving frames. To evaluate motion correction performance, WB dynamic image sequences from 3 different PET/CT systems (Biograph mCT, Biograph Vision 600, and uEXPLORER) using 6 different tracers (18F-FDG, 18F-fluciclovine, 68Ga-PSMA, 68Ga-DOTATATE, 11C-Pittsburgh compound B, and 82Rb) were considered. Motion correction accuracy was assessed using 4 different measures: change in volume mismatch between individual WB image volumes to assess gross body motion, change in displacement of a large organ (liver dome) within the torso due to respiration, change in intensity in small tumor nodules due to motion blur, and constancy of activity concentration levels. Results: Motion correction decreased gross body motion artifacts and reduced volume mismatch across dynamic frames by about 50%. Moreover, large-organ motion correction was assessed on the basis of correction of liver dome motion, which was removed entirely in about 70% of all cases. Motion correction also improved tumor intensity, resulting in an average increase in tumor SUVs by 15%. Large deformations seen in gated cardiac 82Rb images were managed without leading to anomalous distortions or substantial intensity changes in the resulting images. Finally, the constancy of activity concentration levels was reasonably preserved (<2% change) in large organs before and after motion correction. Conclusion: FALCON allows fast and accurate correction of rigid and nonrigid WB motion artifacts while being insensitive to scanner hardware or tracer distribution, making it applicable to a wide range of PET imaging scenarios.
摘要：
我们介绍了快速运动校正算法（FALCON）软件，它允许校正动态全身（WB）图像中的刚性和非线性运动伪影，无论PET/CT系统或示踪剂。方法：使用仿射对准校正运动，然后采用亚纯方法来解决非刚性变形。在这两个步骤中，使用多尺度图像对齐对图像进行配准。此外，通过计算参考帧和其他运动帧之间的初始归一化互相关度量来自动估计适合于成功运动校正的帧。要评估运动校正性能，来自3种不同PET/CT系统的WB动态图像序列(BiographmCT，传记视觉600和uEXPLORER）使用6种不同的示踪剂（18F-FDG，18F-fluciclovine,68Ga-PSMA,68Ga-DOTATATE，11C-匹兹堡大院B，和82Rb)被考虑。使用4种不同的措施来评估运动校正的准确性：单个WB图像体积之间的体积不匹配的变化，以评估总体身体运动，由于呼吸，躯干内的大器官（肝穹顶）的位移变化，由于运动模糊，小肿瘤结节的强度变化，和恒定的活动浓度水平。结果：运动校正减少了全身运动伪影，并将动态帧之间的体积失配减少了约50％。此外，在校正肝脏穹顶运动的基础上评估大器官运动校正，在大约70%的病例中被完全移除。运动矫正也改善了肿瘤的强度，导致肿瘤SUV平均增加15%。在门控心脏82Rb图像中看到的大变形被管理,而不导致在所得图像中的异常畸变或显著的强度变化。最后,在运动校正前后，大器官的活动浓度水平的恒定性得到了合理的保留（<2％的变化）。结论：FALCON可以快速准确地校正刚性和非刚性WB运动伪影，同时对扫描仪硬件或示踪剂分布不敏感，使其适用于广泛的PET成像场景。
