• k : overall cycle #, i.e., k-th iteration of feasibility-seeking and TV perturbations.

• K : total # of cycles, i.e., total # of iterations of feasibility-seeking and TV perturbations.

• n : TV perturbation step #, 1 ≤ n ≤ N.

• xk : image vector x at cycle k.

• $\overline{x}$ : initial iterate x0 of image reconstruction.

• N : # of TV perturbation steps per feasibility-seeking iteration.

• α : perturbation kernel, 0 < α < 1.

• ℓk : perturbation kernel exponent.

• βk,n: perturbation coefficient βk,n = αℓk at TV perturbation step n and feasibility-seeking iteration k.

• ϕ : the target function to which superiorization is applied; here, ϕ = TV, the total variation of the image vector.

• ϕ(xk,n) : TV of image vector xk,n at TV perturbation step n and feasibility-seeking iteration k.

• vk,n : normalized non-ascending perturbation vector for ϕ at xk,n, i.e., ${\upsilon }^{k,n}=\frac{\nabla \varphi (x^{k,n})}{\left|\right|\nabla \varphi (x^{k,n})\left|\right|}={\varphi }^{\prime }(x^{k,n})$

• PT : projection operator representative of an iterative feasibility-seeking algorithm.