“…The iterative algorithms have been further improved over the recent decades by using regularization constraint (Bauer et al, ; Sun et al, ; van den Berg et al, ), multiscaling technique (Caorsi et al, ), wavelet transformation (Li et al, ), etc. As an example, sparsity constraints can be appropriately exploited and compressive sensing‐based techniques are proved to be effective in both qualitative imaging (Gurbuz et al, ; Sun, Kooij, & Yarovoy, ; Sun, Kooij, Yarovoy, et al, ) and quantitative ones (Ambrosanio & Pascazio, ; Oliveri et al, ; Poli et al, ; Sun et al, ). However, it is worth noting that the cost functional remains unchanged in the aforementioned research work, which consists of two error terms: the data error and the state error.…”