POST-INJECTION ATTENUATION CORRECTION FOR PET SCANNERS WITHOUT MEASURED RANDOM CORRECTION

The most accurate attenuation correction in positron emission tomograp hy (PET) is achieved by measuring a transmission scan with a rotating rod source in combination with a blank scan using the rod windowing te chnique. In clinical routine, however, transmission scans often have t o be acquired after the administration of the radiotracer. The raw dat a recorded this way are biased by coincidences generated by the additi onal activity in the scanner's field of view. In a first approximation , these additional true coincidences can be removed by subtracting a d ecay-corrected emission scan from the post-injection transmission data . But there are also additional 'mixed' random events generated by the single photon fluxes from the patient activity and the rod source tog ether. In this work, the correction for post-injection transmission da ta was extended to take into account the effect of the rod windowing a nd the 'mixed' randoms. A couple of experiments were performed to dete rmine the reduced scanner sensitivity for the additional true and rand om events with active rod windowing. The resulting correction, which c an be used for most tomographs without a measured random correction, w as validated in a study with the EEC whole-body phantom.