Simultaneous reconstruction of emission and attenuation images in time-of-flight (TOF) positron emission tomography (PET) does not provide a unique solution. In this study, we propose to solve this limitation by including additional information given by a reference object with known attenuation placed outside the patient. Different configurations of the reference object were studied including geometry, material composition, and activity, and an optimal configuration was defined. In addition, this configuration was tested for different timing resolutions and noise levels. The proposed strategy was tested in 2D simulations obtained by forward projection of available PET/CT data and noise was included using Monte Carlo techniques. Obtained results suggest that the optimal configuration corresponds to a water cylinder inserted in the patient table and filled with activity. In that case, mean differences between reconstructed and true images were below 10%. However, better results can be obtained by increasing the activity of the reference object. This study shows promising results that might allow to obtain an accurate attenuation map from pure TOF-PET data without prior knowledge obtained from CT, MRI, or transmission scans.

中文翻译：

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使用参考对象在飞行时间PET中同时进行发射和衰减重建。

在飞行时间（TOF）正电子发射断层扫描（PET）中同时重建发射和衰减图像并不能提供独特的解决方案。在这项研究中，我们建议通过包括参考对象提供的附加信息来解决此限制，参考对象在患者体外放置有已知衰减。研究了参考对象的不同配置，包括几何形状，材料成分和活动性，并定义了最佳配置。此外，还针对不同的时序分辨率和噪声水平测试了此配置。通过对可用PET / CT数据进行正向投影获得的2D模拟中，对所提出的策略进行了测试，并使用了Monte Carlo技术将噪声包括在内。获得的结果表明，最佳配置对应于插入患者床中并充满活动的水缸。在那种情况下，重建图像与真实图像之间的平均差异在10％以下。但是，可以通过增加参考对象的活动来获得更好的结果。这项研究显示出令人鼓舞的结果，可能无需从CT，MRI或透射扫描获得先验知识即可从纯TOF-PET数据获得准确的衰减图。