Irradiation planning apparatus and irradiation plan correction method

An irradiation planning apparatus for developing an irradiation plan involving a particle beam, the apparatus comprising:

• a three-dimensional scanned data acquisition unit configured to acquire three-dimensional scanned data generated by three-dimensional scanning of an object to be irradiated (hereinafter referred to as irradiated object) of the particle beam by means of a radiation different from the particle beam;
• a prescription data acquisition unit configured to acquire prescription data indicative of a position and a volume of a region irradiated with the particle beam for the irradiated object;
• a reaction-physical-quantity distribution data generation unit configured to generate reaction physical quantity distribution data indicative of a distribution of a physical quantity indicative of capability, of a material of the irradiated object, of reacting with the particle beam on the basis of the three-dimensional scanned data;
• and
• a dose distribution calculation unit configured to calculate a dose distribution on the basis of the prescription data and the reaction physical quantity distribution data,
• wherein
• the reaction-physical-quantity distribution data generation unit includes
• a stopping power ratio correction processing unit configured to convert the three-dimensional scanned data into a stopping power ratio, which is a physical quantity indicative of capability of decelerating incident particles, of a material of interest, relative to corresponding capability of water, and generate three-dimensional stopping power ratio data, and
• an irradiated object material correction processing unit configured to determine, from the three-dimensional stopping power ratio data, a correction factor representing a difference between in water and in an irradiated object material, and perform correction, depending on depth, of a depth dose distribution of the particle beam using the correction factor.