Dual-phase Fluorodeoxyglucose Positron Emission Tomography / Computed Tomography for Differentiation of Tuberculoma from Malignancy in Patients Presenting with Solitary Pulmonary Nodules: Local Experience in a Single Centre

Objective: To evaluate whether dual-phase fluorodeoxyglucose (FDG) positron emission tomography / computed tomography (PET/CT) can differentiate tuberculoma from malignancy in patients presenting with solitary pulmonary nodules. Methods:This was a retrospective study of patients referred to our centre for evaluation of a solitary pulmonary nodule from December 2003 to September 2008. FDG PET/CT studies were performed using a hybrid PET/ CT scanner. Imaging was taken 1 hour and 3.5 hours after injection of the tracer. The maximum standardised uptake value (SUVmax) of the lung lesion in 1 hour and 3.5 hours imaging was designated as SUVe and SUVd, respectively. The difference between them (SUVd – SUVe) was designated as ΔSUV. Results were correlated with the final (histological or clinical) diagnoses. Patients with primary lung cancer and tuberculosis were selected for the analysis. Results:A total of 26 patients (15 males, 11 females) were investigated during the study period. Among them, 21 (10 males, 11 females) had primary bronchogenic carcinoma and 5 had a tuberculoma (all males). They were followed up for a mean duration of 37 months (range, 6 to 63 months). The malignant nodules had a mean SUVe of 5.2 (range, 0.7 to 15.7) and mean SUVd of 6.5 (range, 0.7 to 19.7), respectively. Tuberculomas had a mean SUVe of 5.1 (range, 1.4 to 9.1) and mean SUVd of 5.6 (range, 1.0 to 8.9), respectively. No statistical significance was found between the two patient groups in terms of SUVe (p = 0.871, Mann-Whitney U test). The mean ΔSUV of malignant solitary pulmonary nodules was 1.3 (range, -1.2 to 7.7) while that of tuberculomas was 0.5 (range, -1.8 to 2.3). Thus, there was no statistically significant difference between the two groups in terms of ΔSUV (p = 0.72, Mann-Whitney U test). Conclusions: Tuberculomas behave similarly to solitary malignant pulmonary nodules. Dual-phase FDG PET/ CT cannot accurately differentiate between them.