Fig. 4

Quantitative and qualitative comparison among the reconstruction results from different network architectures. a Layer-wise visualization of the reconstructions from different network architectures, A: 3D U-net structure as the baseline method; and modified 3D U-net by replacing the first convolutional kernels at each hierarchical level in the encoder as B: the combination of \(x-y\), \(y-z\), and \(x-z\) convolution kernels without atrous; C: 3D isotropic atrous module, D: 3D anisotropic atrous module with the same max atrous rate \(a_1 = a_2 = 18\), E–G: 3D anisotropic atrous module with different max atrous rates ((\(a_1 = 24\) and \(a_2 = 30\)), (\(a_1 = 30\) and \(a_2 = 36\)), and (\(a_1 = 36\) and \(a_2 = 42\)), respectively). The results of method E are shown in Fig. 3e. b, c Quantitative comparison of the testing volumes