Fig. 4

Reconstructed images of a set of real eight-channel axial brain data. The acquisition is accelerated with a net reduction factor of 2.77. a Reference image with SoS reconstruction. b GRAPPA reconstruction with 38 ACS lines and 4 outer reduction factor. c GRAPPA reconstruction with 12 ACS lines and 3 outer reduction factor. d Reconstruction using Tikhonov regularization. e Reconstruction using IRLS method. f Reconstruction using AV-GRAPPA. g–k Difference maps of b–f, respectively. Similar to the results in Fig. 3, AV-GRAPPA reduces more noise than GRAPPA, Tikhonov regularization and IRLS method. In addition, since AV-GRAPPA has little ability to reduce aliasing artifacts, a few aliasing artifacts exist in the reconstructed image. But, aliasing artifacts also exist in other reconstructed images, compared to which, AV-GRAPPA keeps the aliasing artifacts at a relatively low level