Treatment planning and delivery workflow steps in MR-guided adaptive RT

Adaptive radiotherapy (RT) is a concept of repeated replanning according to changes in the tumor shape or normal anatomy during a course of fractionated RT. It is mostly applied in an offline fashion, meaning that replanning takes place while the patient is still being treated with the current plan. New imaging technologies, faster contouring, and dose-calculation methods have opened the possibility to perform such tasks while the patient is on the treatment couch and thus the replanning can be performed online to the anatomy-of-the-day. This new concept has been initially introduced with the implementation of hybrid magnetic resonance (MR) linear accelerators. In this chapter, we focus on the different workflow steps, which include reference treatment planning and delivery including image acquisition, segmentation, dose calculation, and image verification. Finally, we touch on quality assurance aspects specific to adaptive replanning and workflow timing aspects.