Towards more accurate 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) imaging in active and latent tuberculosis

Abstract

Tuberculosis (TB) is one of the leading causes of death worldwide. Although the disease is curable and preventable, it is underdiagnosed in many parts of the world. Positron emission tomography (PET) imaging using 18 F-FDG in TB can localise disease sites and the extent of disease. 18F-FDG accumulates in the immune cells that participate in inflammation and granuloma formation, such as activated macrophages and lymphocytes. Therefore, FDG PET/CT scanning is now being evaluated for its usefulness in the diagnosis of extrapulmonary TB and in monitoring the response to treatment. FDG PET/CT imaging is positive and has high sensitivity in active TB, complementing conventional radiological imaging (X-ray, computed tomography, magnetic resonance imaging) in the diagnosis of primary pulmonary, extrapulmonary, and post-primary or miliary TB. FDG PET/CT has low specificity when it is used for solitary pulmonary nodule characterization, and its ability to differentiate TB from malignancy is limited in this setting. Dual point imaging has been proposed as a way to overcome this limitation. FDG PET/CT can reliably differentiate active from inactive disease, and there is promising evidence that it can contribute to the assessment of the response to treatment with an impact on patient management. FDG PET/CT has been found positive in cases of latent TB infection and its ability to identify activation early is currently being explored. More studies are needed to establish the utility of this method in recognizing multidrug-resistant TB cases. Furthermore, other PET radiotracers might prove useful in the functional imaging of TB infection in the future.