Applications of FDG-PET in infection with emphasis on management of tuberculosis

2017 Objectives: 1) Demonstrate different applications of FDG-PET in infection 2) Discuss the utility of FDG-PET imaging in management of tuberculosis (TB). Methods: 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) imaging has been used in diagnosis of many infectious conditions; fever of unknown origin (FUO), osteomyelitis (OM), human immunodeficiency virus & acquired immunity deficiency syndrome (HIV/AIDS), tuberculosis (TB) and others. Conventional techniques as CT and MRI have long been used in diagnosis of such conditions; however, they are limited to the morphological aspect of the disease, besides being limited by lower sensitivity and specificity. PET using the radiotracer FDG provides valuable information on the metabolic behavior of such conditions on a molecular level, detecting activity at the earliest manifestations, allowing early diagnosis, and sparing the need for the relatively late morphological manifestations to be detected by conventional imaging techniques. Global quantitative assessment has been described by Viplav et al. in 2020, this method produces solid parameters that provides a complete idea of the disease burden, through implementation of Region of interest Visualization, Evaluation, and Image Registration (ROVER) method (ABX GmbH, Germany). It allows reproducible 3D region of interest (ROI) determination of the metabolic active lesions seen on PET images. And thus, providing quantitative analysis of the global disease burden, and provides reliable method for response to therapy. Results: Hybrid FDG-PET/CT imaging has superior spatial resolution, and provide correct localization when used in conjunction with CT images. The sensitivity of FDG PET in detection of inflammatory activity is explained by the actual physiological uptake of that is exhibited by organs of the body that have high glucose metabolism, in turn inflammatory processes have enhanced rates of glycolysis, which facilitates their detection utilizing PET FDG imaging, and that causes them to be metabolically active , and to be FDG avid on PET scans, attaining the modality’s advantage over morphological conventional imaging techniques in detecting and diagnosing various infectious conditions. The utility of FDG-PET in diagnosing TB is due to the disease’s FDG-avid behavior, delineating the disease involvement and its extra-pulmonary manifestations. Whole-body PET-imaging also allows monitoring of response to treatment, through the quantification of the global disease burden, permitting assessment of specific treatment regimens. Conclusions: FDG-PET imaging is a non-invasive tool that has great clinical benefit in diagnosis, management, and monitoring of treatment response of various infectious diseases. Also, in terms of histopathological mapping for biopsy sites and characterization of a range of infectious diseases, including TB. Global assessment of disease burden is a novel technique that provides a reliable quantitative analysis of the disease burden, aiding proper monitoring and evaluation of response to treatment.