Reduction of CT artifacts due to respiratory motion in a slowly rotating SPECT/CT

The GE Hawkeye-4 is a low-dose CT system mounted on the gantry of a SPECT scanner. With a scanning time of 23 s per full rotation, which corresponds to 4–5 normal breathing cycles, respiratory motion may induce image artifacts in thorax studies. We have developed a method to reduce these artifacts by correcting for the axial component of the respiratory motion, utilizing respiratory phase information concerning the breathing pattern, obtained by the use of a pneumatic belt-system. The method is based on segmentation of the projection data into subsets corresponding to different motion-amplitudes, followed by generation of low quality, but motion-free image estimates. The method has been tested with simulations based on a digital phantom and also with simulations based on real CT data. Our results show that significant reduction in artifacts can be achieved by correcting for the axial component of the respiratory motion. In conclusion, this is a promising method for reduction of respiratory motion artifacts in a slowly rotating SPECT/CT system.