I. Introduction
Cardiac PET scanning provides images of the human heart that could advance diagnosis of heart diseases such as coronary artery disease (CAD) [1]–[5]. PET imaging with cardiac gating helps reduce motion blurring and has the potential of revealing cardiac motion abnormalities [6] as well as providing additional information on stress and strain [7], [8]. With the combination of cardiac gating techniques and motion correction methods [9]–[13], it is possible to further improve the image quality [6] and the accuracy of diagnostic metrics such as the ejection fraction [14]. For these advanced methods to work, accurate cardiac gating is a prerequisite.