“…These statistics are computed from the histogram of the gray levels of the image and depend only on the individual pixels and not on their neighborhood. In the prostate, first-order statistics have been used in the following models: the intensity profile model [47], gradient models [48,49], models using the gray level threshold of the regions extracted from a neural network [50], a radial basis relief model [51], an instantaneous variation coefficient (ICOV) model [52], a model using the local standard deviation in a multiresolution framework [53], posterior probability models [9,54], mixture probability distribution models [42,43,55,56], or models that are combined in many other ways [13,15,57,58]. Feng et al [49] proposed a weighted combination of gradient and probability distribution functions.…”