Three-dimensional registration of cardiac positron emission tomography attenuation scans

A method is described and tested which allows three-dimensional registration of two cardiac PET attenuation scans of the same subject acquired at different times. The alignment method is based on maximizing the correlation coefficient between the stacks of slices obtained during each of the two imaging sessions. The method appears accurate to better than 1 mm in x, y and z, and better than 1.5 degrees in the three angles of rotation. The method has been tested by using it to realign deliberately misaligned attenuation scans, and also by using realigned attenuation scans to correct fluorodeoxyglucose (FDG) emission scan data. The FDG emission data reconstructed with the realigned attenuation scans do not differ appreciably from the FDG data obtained using the original attenuation data. The method should be useful in realigning emission data (using the alignment coordinates predicted by realigning the attenuation scans), correcting for subject motion between scans (especially multiple intervention scans) and may allow a subject to leave the scanning table between scans during long imaging sessions.