Invertible Ac-Flow: Direct Attenuation Correction Of Pet Images Without Ct Or Mr Images

Attenuation correction can improve the contrast of the positron emission tomography (PET) images and provide valuable information for the diagnosis. Clinically, attenuation correction is performed with computed tomography (CT) or magnetic resonance (MR) images, which requires an additional CT or MR scan. In order to save the cost of scanning and reduce the harm of CT radiation to patients, we proposed invertible AC-flow to obtain attenuation corrected (AC) PET images directly from non-attenuation corrected (NAC) PET images. The overall AC-flow adopted multi-slice inputs to utilize the spatial correlation of adjacent slices, and was consisted of 8 invertible blocks, and each invertible block was made up of a invertible 1Г—1 convolution layer and a enhanced affine coupling layer. Several small U-nets were adopted to learn the transformation parameters of the enhanced affine coupling layers. The proposed AC-flow was validated on a cardiac gated-PET dataset of 13N-Ammonia, and the experimental results showed that the AC-flow was able to obtain AC PET images of high quality, and achieved higher SSIM (0.9202В±0.0592) and PSNR (27.60В±5.10) than DCNN (SSIM: 0.8957В±0.0814, PSNR: 26.66В±6.41) and Deep-DAC (SSIM: 0.8786В±0.1027, PSNR: 25.34В±6.35).