Imaging and Anatomic Considerations for Prostate and Pelvic Organs Contouring

Prostate cancer radiotherapy is evolving to new, highly accurate treatments, allowing physicians to increase the radiation dose to the target and reduce radiation exposure in the adjacent organs. This is facilitated by better technological abilities and improved imaging techniques, leading physicians to better define and contour the volumes they need to treat or avoid. CT-MR image fusion or MRI-only based simulations are becoming more common and widely used and serve as the basis for delineation. There is an increased need for standardized and accurately defined volumes that are visualized by MR imaging. The different prostate structures and zone, as well as surrounding structures such as bladder neck, neurovascular bundle, genitourinary diaphragm and more, should now be assessed routinely by the radiation oncologist when planning radiotherapy treatments. The relevant structures are described with their borders, anatomical landmarks, images and helpful tips, all provided in order to assist the radiation oncologist using MRI-based simulation for contouring.