**1. Introduction**

The purpose of this chapter is to provide the reader with detailed information about imaging of rectal cancer in the context of standardized and novel therapy options of rectal cancer. It is essential to put the rectal cancer in the correct stage group based on different imaging markers- local invasion (T-stage), local infiltration of mesorectum, intra- and extravascular invasion, lymph node spreading. Another important imaging biomarker is the tumor regression grade visualized on magnet-resonance imaging after neoadjuvant therapy. All markers correspond to substantial oncologic parameters such as survival rates. The connecting bridge is magnet-resonance imaging.
