**2. Rectal cancer imaging**

Imaging of rectal cancer is more specific than imaging of the other colonic cancers. Rectal cancer staging is based on two principles. The first is an anatomic definition of the tumor and the second is prognostic stage grouping. Both are achieved by magnet-resonance imaging. Additional imaging modalities such as ultrasound US, computed tomography CT and positron emission tomography PET are discussed later on.
