1. A image processing apparatus comprising:. a geometric correction memory which stores a pre-calculated geometric matrix specific to an imaging apparatus; an attenuation map memory which stores an attenuation map of a subject to be imaged in the imaging apparatus; a buffer which stores a plurality of lines generated by the imaging apparatus to be reconstructed; and a processor which reconstructs the lines into art attenuation corrected image representation of the subject using the lines from the buffer, the attenuation map, and the geometric matrix.