RADIOTHERAPY SYSTEM, DIAPHRAGM IMAGE ANALYSIS APPARATUS AND CONTROL PROGRAM

PROBLEM TO BE SOLVED: To accurately detect the temporal positional deviation of a diaphragm block provided in a multifractionated diaphragm body without being affected by the irregularity of the applied radiation intensity distribution.SOLUTION: The diaphragm image analysis apparatus 3 includes an image data generation part 31 and a positional deviation detection part 35. The image data generation part 31 generates reference image data based on projection data collected by the radiography for the diaphragm block whose end is disposed at a prescribed position, and further generates evaluation image data based on the projection data collected by the radiography for the diaphragm block whose end is disposed at the prescribed position or in the vicinity thereof. The positional deviation detection part 35 detects the positional deviation of the diaphragm block relative to the prescribed position based on positional information of the end of the diaphragm block represented in the reference image data and positional information of the end of the diaphragm block represented in the evaluation image data.