FDG-PET/CT imaging in lung malignancy: The effect of respiratory gating on the Standardised Uptake Values of lung lesions.

Abstract

Background: FDG-PET/CT has gained widespread acceptance as an invaluable tool in the management of oncology patients, in which, the standardised uptake values (SUV) are used to provide a simplistic measure of the metabolic activity of the lesion. However, in the evaluation of lung malignancy, respiratory motion results in a smearing (partial volume) artefact, that leads to underestimation of the lesion SUV. Respiratory gating has been employed as a potential solution. However, literature regarding the effect of respiratory gating on SUVs in lung malignancy is mostly limited to pilot studies with small sample sizes. Objective: To assess the effect of respiratory gating on the SUV of lung lesions in the FDG-PET/CT evaluation of lung malignancy in the clinical setting. Thereby, to provide proof of principle of the effectiveness of respiratory gating in reducing the smearing (partial volume) artefact created by respiratory motion and to determine its ability to provide a more accurate estimation of SUVs in the evaluation of patients with lung malignancy. Method: A retrospective cohort study was conducted on 49 consecutive patients with biopsy proven lung malignancy who underwent both conventional (non-gated) and respiratory gated FDG-PET/CT imaging between December 2018 to June 2019. The maximum SUV, SUVmax, of the lung lesions was recorded from both sets of images. A paired-samples t-test was performed to compare the SUVmax values between the two groups. Results: There was a statistically significant difference in the SUVmax value between the non-gated (M=9.6284, SD=5.13304) and the gated (M =10.4651, SD=5.51711) series; t(48)= -3.755, p = 0.000. These results suggest that respiratory gating does influence the SUVmax of lung lesions. Specifically, our results suggest that when respiratory gating is employed, the SUVmax of lung lesions increases compared to the non-gated value. Conclusion: Respiratory gating is effective in reducing the smearing (partial volume) artefact created by respiratory motion and provides a more accurate estimation of the SUV for lung lesions in the PET/CT evaluation of lung malignancy.