Pelvis

This chapter reviews the key concepts of patient setup, imaging, and treatment planning for pelvic sites, providing guidance on accurately and optimally delivering prescription doses to a variable and complex treatment site. Treatment planning techniques for pelvic targets range from relatively simple 3D conformal radiation therapy for cases with straightforward geometries and single prescription levels to advanced intensity-modulated radiotherapy and volumetric arc therapy approaches, which accommodate complex target volumes and multiple prescription dose levels. The selection of an appropriate planning technique is highly dependent on the location and extent of the target volume. The dynamic nature of internal anatomy in pelvic radiation treatment makes it challenging to deliver robust treatment plans, as significant daily variations can occur in organ position and shape. This chapter addresses how anatomical changes can affect dose delivery and be accounted for in both the planning and treatment phases. Strategies to improve setup reproducibility – such as image guidance, bowel and bladder preparation protocols, and immobilization devices – are essential for ensuring the robustness of the treatment plan and minimizing unintended variations in dose distribution.