Patent Number: 
Section: abstract

Provision is made for a particle-beam treatment system in which, even during particle-beam irradiation, the shape of a multileaf collimator is monitored. The particle-beam treatment system, in which multi-layer conformal irradiation is performed while the setting of the shape of the multileaf collimator in an irradiation head is changed during particle-beam irradiation, is provided with an optical shape-monitoring unit mounted attachably and detachably in the snout portion at the downstream side of the multileaf collimator, the optical shape-monitoring unit having a shape-monitoring mirror, opposing the multileaf collimator, for monitoring the shape of the multileaf collimator; a video camera for shooting the multileaf-collimator shape reflected by the shape-monitoring mirror; and an image monitor for displaying an image of the video camera that shoots the shape of the multileaf collimator.