First start by trying standard filtering-methods. Compare what you get with 2-D median-filter (medfilt2), and Lee's sigma-filter (wiener2) and see how they perform. After doing that you can check different more advanced image-filters on the file-exchange, for example: bilateral filters, Nonlinear Diffusion filters, total variation filtering and on and on. But first use the basic tools then understand their use and the noise-characteristics in your image. Check the help and documentation to medfilt2 and wiener2.
HTH
