PET is a nuclear medical examination which constructs a three-dimensional image of metabolism inside the body; in this article is particular, images are taken from the brain. The high complexity inherent to the interpretation of the brain images makes that any help is important to the specialists in order to accurate the diagnostic. In orden to reach reliable and good images, a normalizacion precess is suggested in this paper, consisting of contring the brain in the three-dimensional image, scaling it according to a template brain and, finally, rotating the brain according to the inclination of the template. For not reducing the quality of the information the application works with PET image format and radioactivity measures instead of translate to an ordinary colour image.