Patent Number: 
Section: claims

1. A particle beam irradiation apparatus in which an incident particle beam is scanned so as to irradiate the particle beam on a target comprising:a particle beam shielding member configured to shield a part of a scanned particle beam;a prompt signal detector configured to detect a prompt signal, said prompt signal being generated when the scanned particle beam collides with the shielding member; anda signal comparison device configured to (1) predict a pattern of generation of a prompt signal having been generated by a pre-determined scanning pattern and (2) obtain the predicted pattern to store thereof as a signal time pattern for comparison,wherein the signal comparison device compares the detected signal time pattern, which is the time pattern of the signal detected by the prompt signal detector when the particle beam is scanned according to the pre-determined scanning pattern and the particle beam is irradiated upon a target, to the stored predicted signal time pattern for comparison, so as to detect an anomaly of the particle beam scanning or that of the particle beam shielding member. 2. The particle beam irradiation apparatus according to claim 1, wherein the particle beam shielding member is a collimator for forming a lateral irradiation field of the particle beam in the target. 3. The particle beam irradiation apparatus according to claim 1, wherein the particle beam is scanned and a lateral irradiation field is formed on the target by the particle beam itself, and the particle beam shielding member is provided in at least one part in the boundary of a scanning region of the particle beam. 4. The particle beam irradiation apparatus according to claim 1, wherein the particle beam shielding member is a prompt radiation signal to be generated. 5. The particle beam irradiation apparatus according to claim 4, wherein the prompt signal detector is provided at the downstream of the particle beam than the particle beam shielding member. 6. The particle beam irradiation apparatus according to claim 5, wherein a rotating gantry mechanism having a counter weight is included, and the prompt signal detector is provided so as to move integrally with the counter weight. 7. The particle beam irradiation apparatus according to claim 1, wherein a display for displaying both of the detected signal time pattern and the signal time pattern for comparison or a display for displaying the difference between the detected signal time pattern and the signal time pattern for comparison is provided. 8. A particle beam therapy system in which the particle beam irradiation apparatus according to claim 1 is provided.