A radiation imaging device includes a radiation source which rotates around a
subject
to be examined and irradiates the subject with radiation, a two-dimensional detector
in which a plurality of detection elements for detecting radiation from the radiation
source are two-dimensionally arranged, and a grid which is placed in front of the
two-dimensional detector to remove scattered radiation of the radiation. This device
performs computation with respect to a subject image obtained by the two-dimensional
detector by using the subject image and a gain image obtained by the two-dimensional
detector, and executes removal of a grid pattern due to the grid and gain correction.
The device reconstructs an image on the basis of the subject image obtained using
the subject image from which a grid pattern due to the grid is removed and which
is gain-corrected.