As the Reference determines the final image resolution, it is recommended to use the higher resolved image as the Reference for avoiding losses in image quality. The user, however, should be aware that the size of the Input series may increase dramatically. For instance, if a dynamic PET study is matched to a 256x256 MRI with thin slices, the size of the resliced PET data can easily grow by a factor of 10. Such big data sets can become a problem for the available RAM, and for subsequent processing steps.