These imperfections can be inherent to the imaging modality (e.g., X-rays offer
low contrast for soft tissues, ultrasound produces very noisy images, and metallic
implants will cause imaging artifacts in MRI) or the result of a deliberate trade-off
during acquisition. For example, finer spatial sampling may be obtained through
a longer acquisition time. However that would also increase the probability of
patient movement and thus blurring. In this paper, we will only be interested
in the processing and analysis of images and we will not be concerned with the
challenging problem of designing optimal procedures for their acquisition.