A positron CT apparatus of this invention includes a first detecting device and a first image processing device for acquiring a 3D image of a first site of interest. Further, a second detecting device and a second image processing device are provided for acquiring a real planar image of the first site of interest and a second site of interest. A calculated planar image calculating device calculates, based on the 3D image, data corresponding only to the first site of interest projected to the real planar image. A correcting device provides a corrected planar image corresponding only to the second site of interest by subtracting the calculated planar image from the real planar image. Thus, the 3D image corresponding to the first site of interest and the corrected planar image with a projection of the second site of interest can be acquired at the same time through one diagnosis.
