Deep learning is an emerging reconstruction method for positron emission tomography (PET) that can tackle complex PET corrections in an integrated procedure. This study optimized the direct PET reconstruction from sinogram on a long axial field of view (LAFOV) PET.
Methods:This study developed a new deep learning architecture to reduce the biases during direct reconstruction from sinograms to images. This architecture is based on an encoder-decoder network and perceptual loss is adopted with pre-trained convolutional layers. It is trained and tested on data of 80 patients acquired from recent Siemens Biograph Vision Quadra PET/CT. The patients were randomly split into a training dataset of 60 patients, the validation dataset of 10 patients, and the test data set of 10 patients. The 3D sinograms were converted into 2D sinogram slices and were used as input to the network, and the vendor reconstructed images were considered as ground truths.The proposed method was compared with DeepPET, a benchmark deep learning method for PET reconstruction.
Results:Compared to the DeepPET, the proposed network significantly reduced the root-mean-squared error (rRMSE) from 0.63 to 0.6 (p<0.01), and the structural similarity index (SSIM) and peak signal-tonoise ratio (PSNR) were improved from 0.93 to 0.95(p<0.01) and from 82.02 to 82.36(p<0.01), respectively. The reconstruction time was approximately 10s per patient, which was shortened by 36 times compared with the reconstruction using the conventional method. The errors of average standardized uptake values (SUV) for lesions between ground truth and the predicted result was reduced from 33.5% to 18.7% (P=0.03), and the error of max SUV was reduced from 32.7% to 21.8% (P=0.02).
Conclusion:The results demonstrated the feasibility of using deep learning to reconstruct images with acceptable image quality and short reconstruction time. It showed that the proposed method can improve the quality of deep learning-based reconstructed images without additional CT images for attenuation and scattering corrections. This learning-based approach may provide the potential to accommodate more complex corrections for LAFOV PET.