Respiratory motion management in PET/CT: applications and clinical usefulness

Although breathing movement can introduce heavy bias in both image quality and quantitation, currently there is lack of interest for the respiratory motion management in PET/CT imaging. The respiratory gating technology has shown significant benefits on image quality, reducing motion related artifacts and increasing quantification. Indeed, many papers have demonstrated that there is a consistent increase of the Standardized Uptake Value (SUV) in gated PET images when compared to ungated ones, particularly for the small lesions located both in liver and in lung. Beside the increase in quantification, respiratory gating can also increase sensitivity, specificity and accuracy of PET/CT. Finally, gated PET/CT can be used for radiation therapy planning, reducing the uncertainty in target definition, optimizing the volume to be treated and reducing the possibility of "missing" during the dose delivery. New technologies, able to define the movement of lesions and organs directly from the PET sinogram, can solve some problems (i.e.: extended acquisition time, radiation exposure) that currently are limiting the clinical use of gated PET/CT. If these new technical improvements for motion compensation will be clinically validated, gated technique could be applied routinely in any PET/CT scan.