Current status and future prospects of multi-dimensional image-guided particle therapy.

In this review article we emphasize the importance of "imaging" and "image guidance" in advanced particle therapy from a clinical point of view. Although the image-guided radiotherapy (IGRT) technology used for photon and particle therapy is closely similar, the focus of its application in the two modalities differs. Here, we emphasize the challenges of IGRT for charged particle beams. Radiological Physics and Technology (RTPE) readers interested in the common technologies of IGRT for photons and protons are referred to the plentiful articles already published. Our present deeper insight into IGRT arose through the collaboration of two particle therapy centers, the National Institute of Radiological Sciences (NIRS) in Japan and the Paul Scherrer Institute (PSI) in Switzerland. We believe that international collaboration in rapidly developing fields such as IGRT provides a broad perspective over a wide range of the uses of such technology.