Fig. 9.

Schematic illustration of the DeepPET architecture by Häggström et al. in 2019 [175]. The arrows collectively represent the two convolution layers. The encoder part initially utilizes larger convolution filter kernel sizes of 7 × 7 in the red arrow and 5 × 5 in the blue arrows to work wider operation in the sinogram space, similar to the global operation with dense connections in the AUTOMAP architecture