Gantry-type particle beam irradiation system and particle beam therapy system comprising same

A gantry type particle beam irradiation system which comprises a gantry and is configured such that a particle beam is extracted from a circular accelerator, in a case where a direction in a circular track plane in the circular accelerator is defined as X direction in a plane which is perpendicular to a travelling direction of the particle beam at an extraction position of the circular accelerator, and the direction which is perpendicular to X direction in a plane which is perpendicular to the travelling direction of the particle beam is defined as Y direction, the particle beam has small emittance in X direction and large emittance in Y direction, and the particle beam which is transported by a particle beam transportation unit is irradiated from the irradiation nozzle installed in the gantry to an irradiation target,

• wherein the irradiation nozzle has a ridge filter,
• an angle of the gantry, with which the particle beam is transported so as for emittance in X direction and emittance in Y direction at the extraction position of the circular accelerator to be separated and to maintain each emittance at a position where the particle beam is incident on the irradiation nozzle, is defined as a reference angle, in the state where the gantry is the reference angle the ridge filter is installed so as for the direction in which emittance in X direction is maintained is tilted to the direction which is perpendicular to a ridge of the ridge filter by a predetermined angle.