An image processing apparatus includes 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 stores a plurality of lines generated by the imaging apparatus to be reconstructed. A processor reconstructs the lines into a attenuation corrected image representation of the subject using the lines from the buffer, the attenuation map, and the geometric matrix.