Management of patient position and respiratory motion

The treatment of patient positional accuracy, including moving targets, is a particular challenge in particle beam treatment. Relevant for particle beam treatment are movements greater than about 0.5 cm that occur within about 4 min (intrafractional) or that change the geometry of the patient from day to day (interfractional). Imaging plays a central role in intra- and interfractional changes. Prior to treatment, it is necessary to estimate the extent of positional variation and build patient-specific motion models. During treatment, it is important to monitor the positional changes and apply the correct approaches to mitigate them. Image registration is required to establish a relationship between images of the same patient taken at different times. Different implementations and resulting ambiguities are introduced. Patient-specific positional variation effects and their mitigation strategies should be considered during treatment planning. In this section, I would like to emphasize the importance of "imaging" and "image guidance" in advanced particle therapy from a clinical point of view.