Respiratory motion gating using true event distribution in PET/CT

In PET/CT imaging, respiratory motion may degrade the quality of PET images. A number of solutions for the motion compensation has been investigated and developed. Gating techniques are used widely in nuclear medicine practice for reducing the effect of respiratory motion on PET image. Data-driven gating is one of the gating techniques that exploits the correlation between acquisition data of PET scan and the respiratory motion. Specifically, a data-driven method compensates for the respiratory motion by use of the system sensitivity feature of a PET scanner to estimate the correlation between the respiratory-motion induced position variation and the geometric sensitivity distribution of the scanner. In this study, we investigate a respiratory-motion gating method that is based on the changes of true events detected by detector rings for different motion phases. This method is motivated by the observation that the number distribution of true coincidences detected by individual detector ring varies along with the respiratory motion positions within the scanner FOV. The effectiveness of the method for reducing motion artifacts and improving image quality is demonstrated by use of simulation studies in which data were generated by use of GATE and NCAT software packages.