The role of ¹⁸F-FDG uptake features in the differential diagnosis of solitary pulmonary lesions with PET/CT.

Background: The aim of this study is to evaluate the value of (18)F-FDG uptake features in the diagnosis of solitary pulmonary lesions.
Methods: One hundred thirty-nine patients with solitary pulmonary lesions were divided into full uptake, circular uptake, multi-focus uptake, mild uptake, and no-uptake groups according to the uptake features of (18)F-FDG in solitary pulmonary lesions. The incidence of benign and malignant lesions and the false-positive and false-negative rates in each group were analyzed. The sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) of the method using (18)F-FDG uptake features combined with maximum standard uptake value (SUVmax) (SUV method) in the differential diagnosis of solitary pulmonary lesions were evaluated.
Results: There were 89 malignant and 50 benign lesions. (1) The malignant incidence of the full uptake group was 84.0% (63/75), and there were significant differences when compared with the other groups except the circular uptake group (16/23) (all P = 0.0001). The benign incidence of the multi-focus and no-uptake groups was 83.3% (10/12) and 82.4% (14/17), respectively, and there were significant differences when compared with the full uptake and the circular uptake groups, respectively (all P < 0.05). The benign incidence of the mild uptake group was 58.3% (7/12), and there were no significant differences when compared with the others except the full uptake group (all P > 0.05). No statistical significance was found between either two of the no-uptake, mild uptake, and multi-focus uptake groups (all P > 0.05). (2) In cases with SUVmax ≥2.5, the false-positive rate in the multi-focus uptake group was 83.3% (10/12), which was significantly higher than in the full uptake (12/75) or circular uptake group (7/23) (all P < 0.05). In cases with SUVmax <2.5, the false-negative rates in the mild and no-uptake groups were 41.7 and 17.6% (P = 0.218). (3) The sensitivity, specificity, accuracy, PPV, and NPV of the method using (18)F-FDG uptake features combined with SUVmax and the single SUV method were 88.7%/91.0%, 62.0%/42.0%, 79.1%/73.4%, 80.6%/73.6%, and 75.6%/72.4%, respectively.
Conclusions: The method using uptake features of (18)F-FDG combined with SUVmax can improve the diagnostic specificity and accuracy of solitary pulmonary lesions. The multi-focus uptake feature maybe a benign sign, which still needs more researches to confirm.