Method and apparatus for acquiring and processing a volumetric scan of a periodically moving object having uneven periods of time are included. A volumetric scan is performed of a periodically moving object. A time interval of a periodic movement of the periodically moving object is identified within the volumetric scan. The volumetric scan is divided into volume subsets based on the time interval. The periodic movement is analyzed to determine a correction between adjacent volume subsets, and the time interval is adjusted based on the correction.