PROBLEM TO BE SOLVED: To simultaneously show the present travel amount of an affected part with the present value of a respiratory signal.SOLUTION: On the basis of a measured respiratory signal and a respiratory travel model stored in a storage part, an estimation part estimates the respiration phase of the respiratory signal and the present position of an affected part of a subject corresponding to the respiratory phase, and a phase marker display part displays a phase marker showing the position of the affected part on a display part. This makes it possible to simultaneously show the present travel amount of the affected part with the present value of the respiratory signal.SELECTED DRAWING: Figure 2
