Date Published: August 25, 2016
Publisher: Public Library of Science
Author(s): Yajuan Sun, Hongjuan Yu, Jingquan Ma, Peiou Lu, Juri G. Gelovani.
The aim of our study was to evaluate the role of 18F-FDG PET/CT integrated imaging in differentiating malignant from benign pleural effusion.
A total of 176 patients with pleural effusion who underwent 18F-FDG PET/CT examination to differentiate malignancy from benignancy were retrospectively researched. The images of CT imaging, 18F-FDG PET imaging and 18F-FDG PET/CT integrated imaging were visually analyzed. The suspected malignant effusion was characterized by the presence of nodular or irregular pleural thickening on CT imaging. Whereas on PET imaging, pleural 18F-FDG uptake higher than mediastinal activity was interpreted as malignant effusion. Images of 18F-FDG PET/CT integrated imaging were interpreted by combining the morphologic feature of pleura on CT imaging with the degree and form of pleural 18F-FDG uptake on PET imaging.
One hundred and eight patients had malignant effusion, including 86 with pleural metastasis and 22 with pleural mesothelioma, whereas 68 patients had benign effusion. The sensitivities of CT imaging, 18F-FDG PET imaging and 18F-FDG PET/CT integrated imaging in detecting malignant effusion were 75.0%, 91.7% and 93.5%, respectively, which were 69.8%, 91.9% and 93.0% in distinguishing metastatic effusion. The sensitivity of 18F-FDG PET/CT integrated imaging in detecting malignant effusion was higher than that of CT imaging (p = 0.000). For metastatic effusion, 18F-FDG PET imaging had higher sensitivity (p = 0.000) and better diagnostic consistency with 18F-FDG PET/CT integrated imaging compared with CT imaging (Kappa = 0.917 and Kappa = 0.295, respectively). The specificities of CT imaging, 18F-FDG PET imaging and 18F-FDG PET/CT integrated imaging were 94.1%, 63.2% and 92.6% in detecting benign effusion. The specificities of CT imaging and 18F-FDG PET/CT integrated imaging were higher than that of 18F-FDG PET imaging (p = 0.000 and p = 0.000, respectively), and CT imaging had better diagnostic consistency with 18F-FDG PET/CT integrated imaging compared with 18F-FDG PET imaging (Kappa = 0.881 and Kappa = 0.240, respectively).
18F-FDG PET/CT integrated imaging is a more reliable modality in distinguishing malignant from benign pleural effusion than 18F-FDG PET imaging and CT imaging alone. For image interpretation of 18F-FDG PET/CT integrated imaging, the PET and CT portions play a major diagnostic role in identifying metastatic effusion and benign effusion, respectively.
Pleural effusion caused by a number of malignant and benign diseases is a common and challenging medical problem. In clinic, a series of diagnostic assessments are of great importance for the rational treatment. Above all, differential diagnosis that distinguishes malignant from benign pleural effusion is the first problem which has to be solved. Computed tomography (CT) and positron emission tomography (PET) as noninvasive methods have been used in characterizing pleural effusion as malignancy or benignancy, and can trigger the determination of etiology in some cases [1,2]. PET/CT scanner combining in-line PET and CT cameras provides functional and anatomic/morphologic imagings, and is a new device with considerable diagnostic potential . Several studies have been implemented to discuss the role of PET/CT using 18F-fluoro-2-deoxy-D-glucose (18F-FDG) in assessing the nature of pleural effusion [4,5,6,7,8]. However, their purposes were to evaluate a series of parameters such as density of the effusion, morphology of any solid pleural abnormality and increased uptake of 18F-FDG in pleural effusion and pleura, and the solid pleural abnormality and pleural uptake were significant parameters used for differentiation [4,5]. However, their results were displayed in the form of 18F-FDG PET or CT alone. So far, the method that integrates pleural abnormality on PET imaging with that on CT imaging in the differential diagnosis of pleural effusion has not been explored. We performed this study to determine whether 18F-FDG PET/CT integrated imaging could effectively distinguish malignant from benign pleural effusion. In addition, the diagnostic role of CT and PET portions from 18F-FDG PET/CT integrated imaging remains to be inexplicit, when interpreting the diagnostic results of 18F-FDG PET/CT integrated imaging. Thus, the other purpose of the current study was to investigate the diagnostic role of CT and PET portions from 18F-FDG PET/CT integrated imaging in the differential diagnosis of pleural effusion.
18F-FDG PET/CT imaging as a method of differential diagnosis has been reported to distinguish malignant from benign pleural effusion [4,5,6,7], and the presences of pleural abnormality on CT imaging and pleural region uptake on 18F-FDG PET imaging are found to be the most accurate criteria in determining the malignant nature of pleural effusion [4,5]. However, the efficacy of 18F-FDG PET/CT imaging are displayed in the form of 18F-FDG PET and CT alone. For instance, Toaff et al.  reported a 18F-FDG PET/CT study of 31 patients with primary extrapleural malignancy and pleural effusion, and found that the sensitivities of pleural uptake on PET imaging and pleural lesion on CT imaging were 86% and 71%, respectively, and the specificity was 90% for both of the 2 parameters. Kim et al.  reported that the sensitivity and specificity of 18F-FDG PET imaging was 87.5% and 88.8%, respectively, and the respective sensitivity and specificity of CT imaging was 83.3% and 88.8%. The difference of the present study from previous studies was the method for image interpretation of 18F-FDG PET/CT imaging in identifying the nature of pleural effusion, and the diagnosis results of 18F-FDG PET/CT imaging were determined by synthesizing the degree and form of pleural 18F-FDG uptake on PET imaging and pleural morphologic manifestation on CT imaging. By this means, we found that 18F-FDG PET/CT integrated imaging with sensitivity of 93.5% and specificity of 92.6% showed superior sensitivity to CT imaging alone and higher specificity than PET imaging alone, respectively. The work presented here demonstrated that 18F-FDG PET/CT integrated imaging was a more reliable diagnostic method than 18F-FDG PET and CT imagings in the differential diagnosis of pleural effusion.
In differentiating malignant from benign pleural effusion, 18F-FDG PET/CT integrated imaging is a more useful modality than 18F-FDG PET imaging and CT imaging alone. When interpreting images of 18F-FDG PET/CT integrated imaging, the PET and CT portions play a major role in detecting metastatic effusion and benign effusion, respectively. CT imaging can be used to correct the false-positive findings on PET imaging and improve the specificity with the sensitivity not being reduced.