A computer tomography apparatus of this invention includes an x-ray tube configured
to emit x-rays while rotating around an object to be examined, a radiation detector
configured to have detection elements arranged in a plurality of rows along a slice-thickness
direction, each row having a plurality of the detection elements configure to detect
x-rays that had passed through the object, a data acquisition system configured
to acquire projection data of the object using the output of the radiation detector,
and a reconstructing unit configured to be capable of a first reconstruction method
and a second reconstruction method, reconstruct an image based on the projection
data using one of the first and second reconstruction method, wherein the x-rays
are assumed to intersect perpendicularly with an axis of rotation of the x-ray
tube in the first reconstruction method, and the second reconstruction method reconstructs
the image using a cone angle information of the x-rays.
