Value of 4-dimensional 18F-FDG PET/CT in the classification of pulmonary lesions

Our aim was to evaluate the effect of 4-dimensional (4D) (18)F-FDG PET/CT in the detection of pulmonary lesions.

Fifty-seven pulmonary lesions were prospectively assessed in 37 patients (26 men and 11 women) with a mean age of 66.3 y. Twenty-nine of these patients had a history of neoplasm. All patients underwent 3-dimensional (3D) total-body PET/CT and 4D thoracic PET/CT (synchronized with respiratory movement). Maximum standardized uptake value (SUVmax) was obtained for each lesion in both studies. For the 4D studies, we selected the SUVmax in the respiratory period with the highest uptake ("best bin") and the average value over all bins ("average gated"). SUVmax percentage difference between 3D and 4D PET/CT and the relationship of this value to the diameter and location of the lesions were calculated. Statistical parameters were calculated for 3D and 4D PET/CT.

Fifty-four of 57 lesions showed an increase of SUVmax in the 4D study with respect to the 3D study. The mean SUVmax was 3.1 in the 3D study. 4D PET/CT studies showed a mean SUVmax of 4.5 for the best-bin study and 3.9 for the average gated study. The percentage difference in mean SUVmax between 3D and 4D studies (best bin and averaged gated) was 72.9% and 48.8%, respectively. The smaller the lesion, the greater was the SUVmax percentage difference (P < 0.05). However, no statistical differences dependent on the location of the lesions were observed. Final diagnosis showed that 37 lesions were malignant. The sensitivity, specificity, positive predictive value, and negative predictive value were 37.8%, 95%, 93%, and 45%, respectively, for 3D studies and 70.3%, 70%, 81.2%, and 56%, respectively, for 4D best-bin studies.

Characterization of malignant lung lesions was better with 4D PET/CT than with standard PET/CT.