“…have physical interpretation, factorization indeterminacies must be reduced to TT -1 =PΛ, whereas P is permutation matrix and Λ is diagonal matrix. These are standard indeterminacies in blind source separation and can be achieved if either sparseness, [5,[7][8][9], or statistical independence, [1,3,6], constraints are imposed on S. Sparseness constraints imply that at each pixel location (i 1 ,i 2 ) only few organs exists. In CT imaging, where pixel footprint is small, it is justified to assume that only one organ occupies each pixel footprint.…”