Sci‐Sat AM(1): Imaging‐04: Respiratory errors in cardiac PET/CT with manual alignment of the CT image

Respiratory motion can produce misregistration errors between CT and PETimages in cardiac PET/CT imaging. The objective of this study was to determine if manual registration of a single‐phase end‐expiration CT scan to the PETimage would eliminate respiratory‐induced artifacts. Listmode data from 71 cardiac PET patient scans were rebinned into a 8‐frame respiratory‐gated image series based on a respiratory trigger signal obtained with an optical tracking system. CT‐based attenuation correction (AC) was performed after registering the CTimage with the mean position of the PETimages. The 8 phases of the gated PET study were coregistered and the breathing motion was measured. Images from end‐inspiration and end‐expiration were compared to assess the effect of motion. Studies in which the motion was >8mm were reconstructed again, with the CT scan aligned to end‐expiration or end‐inspiration, to determine if phase‐specific registration could reduce the residual errors. The motion was found to be greatest in the axial direction (mean 4.1mm +\− 1.8mm) and 4 Rb stress studies (17%) had motion >8mm. The maximum displacement during breathing was greater for Rb‐stress imaging ( 8mm of motion. Phase‐specific registration of the CT reduced the extent of the errors but did not fully resolve them, suggesting that more sophisticated AC is required.