Fig. 2.

Role of continuation: In (i), we study the evolution of the cost in (3) and the SER_ROI as a function of the CPU run time using different continuation strategies with the zero filled direct IFFT reconstruction as the initialization. Here, we compare the proposed continuation strategy of updating α, β against other strategies of not performing continuation on either one of the two parameters α, β. It can be seen that the scenarios without continuation depict poor convergence and result in undesirable solutions (see i.(d,e,f)). In contrast, it can be seen from i.(a,b,c) that the continuation over both α, β depicts improved convergence and obtains a solution in i.(c) that is free of artifacts and blur. Further in (ii), we show the cost in (3) and SER_ROI versus CPU run time with the proposed continuation scheme for different initializations. It can be seen that the algorithm converged to approximately the same solution irrespective of the choice of the initialization; the robustness to the initialization is attributed to the continuation rules which ensures a gradual update of the complexity of the problem.