To develop a working fixed point algorithm for (3.1), we will first analyze unconditionally stable time-marching schemes based on convexity-splitting ideas developed in [27, 28] (the idea was also adapted for a different imaging problem by Bertozzi, Esedog ̄lu, and Gillet [6]). The resulting semi-implicit scheme (5.3) improves the stability of time-marching schemes in such a way that stability of (5.3) is guaranteed for all possible time steps. To put it simply, we solve