Iwao Yuma, Akamatsu Go, Tashima Hideaki, Takahashi Miwako, Yamaya Taiga
Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, Chiba, Japan.
Radiol Phys Technol. 2022 Jun;15(2):125-134. doi: 10.1007/s12194-022-00654-6. Epub 2022 Mar 3.
Marker-less head motion correction methods have been well-studied; however, no reports discussing potential issues in positional calibration between a PET system and an external sensor remain limited. In this study, we develop a method for positional calibration between the PET system and an external range sensor to achieve practical head motion correction. The basic concept of the developed method involves using the subject's face model as a marker not only for head motion detection but also for the system positional calibration. The face model of the subject, which can be obtained easily using the range sensor, can also be calculated from a computed tomography (CT) image of the same subject. The CT image, which is acquired separately for attenuation correction in PET, has the same coordinates as the PET image because of the appropriate matching algorithm between CT and PET images. The proposed method was implemented in the helmet-type PET and the motion correction accuracy was assessed quantitatively using a mannequin head. The phantom experiments demonstrated the performance of the developed motion correction method; high-resolution images with no trace of the applied motion were obtained as if no motion was provided. Statistical analysis supported the visual assessment results in terms of the spatial resolution, contrast recovery; uniformity, and the results implied that motion with correction slightly improved image quality compared with the motionless case. The tolerance of the developed method against potential tracking errors had a minimum 10% difference in the amplitude of the rotation angle.
无标记头部运动校正方法已得到充分研究；然而，关于正电子发射断层扫描（PET）系统与外部传感器之间位置校准潜在问题的报道仍然有限。在本研究中，我们开发了一种PET系统与外部距离传感器之间的位置校准方法，以实现实际的头部运动校正。所开发方法的基本概念是将受试者的面部模型用作标记，不仅用于头部运动检测，还用于系统位置校准。受试者的面部模型可以使用距离传感器轻松获取，也可以从同一受试者的计算机断层扫描（CT）图像中计算得出。由于CT图像和PET图像之间有适当的匹配算法，为PET中的衰减校正单独获取的CT图像与PET图像具有相同的坐标。所提出的方法在头盔式PET中得以实现，并使用人体模型头部对运动校正精度进行了定量评估。模型实验证明了所开发的运动校正方法的性能；获得了没有施加运动痕迹的高分辨率图像，就好像没有提供运动一样。统计分析在空间分辨率、对比度恢复和均匀性方面支持了视觉评估结果，结果表明与静止情况相比，经过校正的运动略微提高了图像质量。所开发的方法对潜在跟踪误差的容忍度在旋转角度幅度上至少有10%的差异。
