The value of fluorine-18 fluorodeoxyglucose positron emission tomography/magnetic resonance imaging (F-FDG PET/MRI) in characterising pleural effusion and detecting pleural metastasis for staging lung cancer.

[AIM] Positron emission tomography/magnetic resonance imaging (PET/MRI) combines the anatomical imaging of MRI with the metabolic information of PET. This study aimed to investigate the diagnostic value of PET/MRI in characterising pleural effusions and detecting pleural nodules, which is critical for staging and management in patients with primary pulmonary masses.

[MATERIALS AND METHODS] A total of 29 patients were enrolled in the study from June 2021 to June 2023. A 3-T hybrid PET/MRI including axial respiratory-triggered fast-spin echo T2-weighted imaging (T2WI), axial respiratory triggered T2 fat-suppressing sequence (T2FS), and echo-planar imaging diffusion-weighted imaging (DWI) with b values of 50 and 800 sec/mm. The maximum standardised uptake value (SUVmax) for all lesions (including primary lung lesions and pleural effusion) was measured on PET images. The signal of pleural effusion on T2FS and localised high signals of the pleura on DWI sequences were evaluated by experienced physicians through visual assessment of the MRI sequences.

[RESULTS] SUVmax, T2FS signal, apparent diffusion coefficient (ADC), and DWI signal exhibit significant differences between inflammatory lesions and tumour-related pleural effusions, with sensitivities of 78.95%, 94.74%, 68.42%, and 84.21%, respectively; specificities of 100%, 50%, 80%, and 100%, respectively; and accuracies of 86.21%, 79.31%, 72.41%, and 89.66%, respectively.

[CONCLUSION] Fluorine-18 fluorodeoxyglucose (F-FDG) PET/MRI demonstrates high diagnostic performance in characterising pleural effusions and detecting malignant pleural involvement. Moreover, F-FDG PET/MRI showed a higher diagnostic performance compared with PET/CT in identifying pleural metastases for staging lung cancer combined with pleural effusion.