Updates on 18F-FDG-PET/CT as a clinical tool for tuberculosis evaluation and therapeutic monitoring

Abstract

Tuberculosis (TB) is currently the world's leading cause of infectious mortality. The complex immune response of the human body to Mycobacterium tuberculosis (M.tb) results in a wide array of clinical manifestations, thus the clinical and radiological diagnosis can be challenging. ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG-PET) scan with/without computed tomography (CT) component images the whole body and provides a metabolic map of the infection, enabling clinicians to assess the disease burden. ¹⁸F-FDG-PET/CT scan is particularly useful in detecting the disease in previously unknown sites, and allows the most appropriate site of biopsy to be selected. ¹⁸F-FDG-PET/CT is also very valuable in assessing early disease response to therapy, and plays an important role in cases where conventional microbiological methods are unavailable and for monitoring response to therapy in cases of multidrug-resistant TB or extrapulmonary TB. ¹⁸F-FDG-PET/CT cannot reliably differentiate active TB lesion from malignant lesions and false positives can also be due to other infective or inflammatory conditions. ¹⁸F-FDG PET is also unable to distinguish tuberculous lymphadenitis from metastatic lymph node involvement. The lack of specificity is a limitation for ¹⁸F-FDG-PET/CT in TB management.

Keywords: Tuberculosis (TB); fluorine-18 fluorodeoxyglucose (18F-FDG); latent tuberculosis (latent TB); positron emission tomography and computed tomography (PET and CT); treatment response.

Figure 1

Pulmonary tuberculosis (a lung pattern) in a 59-year-old man. Axial CT (upper row) and axial PET/CT (lower row) and coronal PET (right one) images show intense FDG uptake in the right lung lesions and slight FDG uptake in left lung lesions. Slight FDG uptake in the mediastino-hilar lymph nodes uptake is also observed. FDG, fluorodeoxyglucose; PET, positron emission tomography; CT, computed tomography.

Figure 2

Axial CT and axial and also coronal FDG PET/CT images in a 42-year-old man show military pulmonary involvement in the lower lobes of both lungs (a lung pattern). FDG, fluorodeoxyglucose; PET, positron emission tomography; CT, computed tomography.

Figure 3

Disseminated tuberculosis (a lymphatic pattern) in a 57-year-old man. Multiple liver tuberculous lesions observed on axial CT image (upper row) show intense FDG uptake on axial PET/CT (lower row) and coronal PET (right one) images. FDG uptake in mediastino- retroperitoneal lymph nodes is also seen. FDG, fluorodeoxyglucose; PET, positron emission tomography; CT, computed tomography.

Figure 4

Pulmonary tuberculosis in a 61-year-old man. Axial CT (A) and axial ¹⁸F-FDG-PET/CT (B) show multiple FDG-avid pulmonary lesions. There is a consolidation with central cavitation-peripheral FDG concentration and central cold areas in the right lung suggesting an active disease. FDG, fluorodeoxyglucose; PET, positron emission tomography; CT, computed tomography.

Figure 5

Pulmonary tuberculoma in a 59-year-old man. A nodule in right lower lobe with high FDG uptake observed on axial CT (A) and axial PET/CT (B) images mimics a lung cancer. FDG, fluorodeoxyglucose; PET, positron emission tomography; CT, computed tomography.

Figure 6

¹⁸F-FDG-PET/CT in a 61-year-old man with TB. A mass in the right lower lobe observed on axial CT image with intense FDG uptake on axial PET/CT and coronal PET images mimics a lung cancer. There are high uptake in the hilar lymph nodes, cervical lymph nodes and also bilateral parotid glands. FDG, fluorodeoxyglucose; PET, positron emission tomography; CT, computed tomography.

Figure 7

Axial and sagittal CT images and also axial and sagittal ¹⁸F-FDG-PET/CT images in a 45-year-old woman with tuberculous spondylodiscitis and vertebral bone destruction. FDG, fluorodeoxyglucose; PET, positron emission tomography; CT, computed tomography.

Figure 8

Axial and coronal CT and also axial ¹⁸F-FDG-PET/CT in a 47-year-old woman show tuberculosis involving lung, brain, and meninges. FDG, fluorodeoxyglucose; PET, positron emission tomography; CT, computed tomography.

Figure 9

Axial CT and axial ¹⁸F-FDG-PET/CT and coronal PET images in a 48-year-old woman with tuberculous pericarditis. Slight FDG uptake in the mediastinal lymph nodes is also noted. FDG, fluorodeoxyglucose; PET, positron emission tomography; CT, computed tomography.

Figure 10

Axial CT, axial ¹⁸F-FDG-PET/CT and coronal PET images in a 48-year-old woman with tuberculosis involving cervical lymph nodes. FDG, fluorodeoxyglucose; PET, positron emission tomography; CT, computed tomography.

Figure 11

¹⁸F-FDG-PET/CT images of a 29-year-old woman who was the daughter of an active TB case and diagnosed with latent tuberculosis infection. (A) Coronal CT images. (B) Coronal PET images. (C) Coronal PET/CT fused images demonstrating FDG uptake in the right paratracheal region (blue arrow) and in the right hilar region (red arrow). Top panels are the initial study, and bottom panels are the study after 3 months of treatment with isoniazid demonstrating reduction in ¹⁸F-FDG uptake. Reproduced with permission from (31). FDG, fluorodeoxyglucose; PET, positron emission tomography; CT, computed tomography.

Figure 12

Axial chest CT and axial ¹⁸F-FDG-PET/CT images of two subjects with old healed TB show high ¹⁸F-FDG uptake. Fibrotic scar and calcified nodules suggesting old healed TB in the right upper lobe is observed on the chest CT (A) of a 76-year-old man without a history of TB. The SUVmax of the lesions was measured as 4.0 by ¹⁸F-FDG PET/CT (B). Both the TST and IGRA were negative. Fibrotic scar and nodules in the right upper lobe are observed on the chest CT (C) of a 71-year-old man. He was treated for pulmonary TB 25 years earlier. The SUVmax of the lesions was measured as 2.2 by ¹⁸F-FDG PET/CT (D). Both the TST and IGRA were positive. Reproduced with permission from (37). TST, tuberculin skin test; IGRA, interferon-γ release assay; FDG, fluorodeoxyglucose; PET, positron emission tomography; CT, computed tomography.

Figure 13

¹⁸F-FDG PET/CT in a 35-year-old woman with multidrug-resistant (MDR) tuberculosis before (A) and after (B) 1 month of anti-tuberculosis treatment. Regression of pulmonary and lymph node pathological foci are observed at the follow-up scan (B). Reproduced with permission from (44). FDG, fluorodeoxyglucose; PET, positron emission tomography; CT, computed tomography.