Siemens Healthcare USA, Molecular Imaging, Knoxville, TN, USA.
Phys Med Biol. 2013 Jun 7;58(11):3649-69. doi: 10.1088/0031-9155/58/11/3649. Epub 2013 May 7.
The simultaneous PET data reconstruction of emission activity and attenuation coefficient distribution is presented, where the attenuation image is constrained by exploiting an external transmission source. Data are acquired in time-of-flight (TOF) mode, allowing in principle for separation of emission and transmission data. Nevertheless, here all data are reconstructed at once, eliminating the need to trace the position of the transmission source in sinogram space. Contamination of emission data by the transmission source and vice versa is naturally modeled. Attenuated emission activity data also provide additional information about object attenuation coefficient values. The algorithm alternates between attenuation and emission activity image updates. We also proposed a method of estimation of spatial scatter distribution from the transmission source by incorporating knowledge about the expected range of attenuation map values. The reconstruction of experimental data from the Siemens mCT scanner suggests that simultaneous reconstruction improves attenuation map image quality, as compared to when data are separated. In the presented example, the attenuation map image noise was reduced and non-uniformity artifacts that occurred due to scatter estimation were suppressed. On the other hand, the use of transmission data stabilizes attenuation coefficient distribution reconstruction from TOF emission data alone. The example of improving emission images by refining a CT-based patient attenuation map is presented, revealing potential benefits of simultaneous CT and PET data reconstruction.
本文提出了一种同时重建发射活动和衰减系数分布的正电子发射断层扫描（PET）数据方法，其中衰减图像通过利用外部透射源进行约束。数据是在飞行时间（TOF）模式下采集的，原则上允许将发射和透射数据分离。然而，这里所有的数据都是一次性重建的，不需要在射线图空间中追踪透射源的位置。发射数据和透射源之间的污染是自然建模的。衰减的发射活动数据也提供了有关物体衰减系数值的附加信息。该算法在衰减和发射活动图像更新之间交替。我们还提出了一种从透射源估计空间散射分布的方法，通过结合对衰减图值的预期范围的了解。来自西门子 mCT 扫描仪的实验数据重建表明，与数据分离相比，同时重建可以提高衰减图图像质量。在所示的示例中，衰减图图像噪声降低，并且由于散射估计而发生的非均匀性伪影被抑制。另一方面，透射数据的使用稳定了仅从 TOF 发射数据进行的衰减系数分布重建。通过改进基于 CT 的患者衰减图来呈现改善发射图像的示例，揭示了同时进行 CT 和 PET 数据重建的潜在好处。
