how to calculate psnr in your paper?

[qiuwenyuan19921106]

After reading your paper and codes, i'm strange about the calculation of PSNR. I use some mri data to test the ZF reconstruction and try to calculate the NMSE in your codes, it seems right. But when I calculate the PSNR based on your NMSE or RMSE defined by myself, it seems wrong. What's more, don't you think the PSNR is too high via ZF reconstruction with 20% data kept, because when PSNR reaches 34dB, pictures may seem very similar.