Rebinning and reconstruction techniques for 3D TOF-PET

The measured time difference in 3D Time-of-Flight (TOF) positron emission tomography (PET) makes it possible to improve the signal-to-noise ratio of reconstructed images. The improvement in signal-to-noise ratio will probably be used to reduce imaging time. To keep up with workflow there will be a need for faster reconstruction methods. A variety of reconstruction and rebinning methods have been developed in the past for 2D and 3D TOF-PET data. The TOF information makes very simple reconstruction methods possible. These allow real time reconstruction but the obtained image quality is lower. Relative fast reconstructions can be obtained using rebinning techniques. Fully 3D iterative listmode reconstruction makes no approximations but comes at the expense of long reconstruction times. Data from Monte Carlo simulations of 3D TOF-PET scanners are used to quantify differences in noise and contrast between the different methods. Real time methods are useful for direct display after or even during acquisition, but do not generate useful data for reviewing. Rebinning methods can be used to reduce the reconstruction time with a small loss in image quality and the image quality loss is quite small if good timing resolution can be achieved. Fully 3D iterative listmode reconstruction maximizes the obtained image quality and should be used if not even a small loss in image quality is acceptable. When timing resolution is improved the difference between the different methods become clearly smaller and in the limit where timing resolution is equal to spatial resolution, the methods are equivalent.