Respiratory Gating and the performance of PET/CT in pulmonary lesions

Objective: Aim of this paper was to evaluate advantages of RG technique on PET/CT performance in lung lesions. The impact of 4D-PET/CT for diagnosis (metabolic characterization), staging and re-staging lung cancer were also assessed, including its application for radiotherapy planning. Finally, new technologies for respiratory motion management were also discussed Methods: A comprehensive electronic search of the literature was performed by using Medline database (PubMed) searching "PET/CT" and "gated" and "lung". Original articles, review articles, and editorials published in the last 10 years were selected, included and critically reviewed in order to select relevant articles. Results: Many papers compared Standardized Uptake Value (SUV) in gated and ungated PET studies showing an increase in SUV of gated images, particularly for the small lesions located in medium and lower lung. In addition, other features as Metabolic Tumor Volume (MTV), Total Lesion Glycolysis (TLG) and textural-features presented differences when obtained from gated and ungated PET acquisitions. Beside the increase in quantification, gating techniques can determine an increase in the diagnostic accuracy of PET/CT. Gated PET/CT was evaluated for lung cancer staging, therapy response assessment and for radiation therapy planning. Conclusion: New technologies able to track motion of organs lesion directly from raw PET data, can reduce or definitively solve problems (i.e.: extended acquisition time, radiation exposure) currently limiting the use of gated PET/CT in clinical routine.