Background and Objective: Motion due to patient’s breathing can introduce heavy bias in
PET/CT, both in image quality and quantitation. This paper is a review of the main technical solutions
available to manage movement in PET/CT studies: a) Respiratory Gated (RG), b) Motion Free (MF), c)
End Expiration (EE), d) Banana Artefact Management (BAM) and e) Data Driven Gating (DDG).
Methods: The most diffused solutions (RG, MF and EE) are based on LIST mode acquisition of a PET
Field of View (4D FOV), centered on the anatomical region of interest; to link PET data not only to
time and to spatial position but also to the corresponding breathing phase, the synchronized acquisition
of the patient’s breathing curve is performed by an external tracking device. Different commercial tools
to track and to record patient breathing cycle are available to associate the internal organ motion with a
measurable external parameter; for example these systems can measure the pressure on a chest elastic
belt, the air flow trough patient nose, the breath-in and breath-out air temperature or the markers movement
on the thorax/ abdominal region. Recently DDG techniques are developed to correct respiratory
motion without the help of external motion tracking devices and to obtain a comparable result to that
based on standard RG protocols.
Results: The final result of an RG or DDG protocol is a sequence of 3D images showing organs and
lesions movement; using the other motion management options a single 3D motion-free image is obtained
without motion artefacts and degradation. Compared to the previously described options the
BAM solution is not a real motion management protocol but just a Banana Artefact correction technique
obtained using an Attenuation Correction Map calculated merging the Whole Body Helical CT with a
Cine CT on the diaphragm area.
Conclusion: The motion management in PET/CT imaging shows benefits in terms of image quality,
quantification and lesion detectability and it is useful both in diagnostic and radiotherapy planning.