1. A signal processing method, comprising: acquiring undersampled data corresponding to an object; initializing a first image solution and a second image solution; determining a linear combination solution based upon the first image solution and the second image solution; generating a plurality of selected coefficients by iteratively updating the first image solution, the second image solution and the linear combination solution and adaptively thresholding one or more transform coefficients utilizing the undersampled data, an updated first image solution, an updated second image solution and an updated linear combination solution; and reconstructing a data signal using the plurality of selected coefficients.