Applications of f luorodeoxyglucose-PET imaging in the detection of infection and inflammation and other benign disorders Hongming Zhuang, MD, PhD, Jian Q. Yu, MD, Abass Alavi, MD * Division of Nuclear Medicine, Department of Radiology, Hospital of the University of Pennsylvania, 110 Donner Building, 3400 Spruce Street, Philadelphia, PA 19104, USA Fluorodeoxyglucose-PET (FDG-PET) has evolved into one of the major imaging modalities commonly used in the management of a variety of malignancies [1,2]. This application stems from proved phenom- enon of increased glucose metabolism in malignant cells [3]. Increased glucose metabolism, however, is not specific for tumor cells and in particular inflam- matory cells using glucose as a main source of energy. Inflammatory cells usually demonstrate relatively low glucose uptake in the resting state, but increase sig- nificantly following in vivo or in vitro stimulation [4,5]. Inflammatory and infectious processes are frequently noted to have increased glucose metabo- lism and as a result cause false-positive interpretation of FDG-PET images when they are acquired for the evaluation of patients with various malignancies [6]. In fact, FDG uptake by the inflammatory cells is partly responsible for the overall increased FDG uptake by the malignant lesions. Kubota et al [7] have demonstrated that reactive inflammatory macro- phages and leukocytes around the tumor are noted to have higher FDG uptake than the viable malignant cells in the same tissue sample. Animal experiments also have demonstrated that tumors in athymic nude mice that lack T lymphocytes are noted to have significantly less FDG uptake than that in the normal mice [8]. Initiating steroid hormone treatment, which is known to induce T cell apoptosis, has no effect on the tumor uptake in the athymic immunodeficient mice, whereas it significantly reduces the tumor uptake in the immunocompetent mice [8,9]. These data suggest that the high tumor uptake of FDG ob- served in the immunologically intact subjects par- tially represents increased glucose metabolism in the infiltrating inflammatory cells within the tumor tissue, including T lymphocytes. Animal experiments also indicate that FDG uptake is higher in the infection site than that of any other radiotracers tested, includ- ing gallium, radiolabeled serum albumin, thymidine, and amino acid S-methionine [10]. Numerous reports have demonstrated increased FDG uptake at the sites of infection and inflamma- tion. FDG is applicable to almost any type of infection or inflammation or any anatomic location, including the following: abscesses [11 – 17], pneumo- nia [18 – 20], tuberculosis [21 – 25], Mycobacterium avium-intracellulare infection [26 – 28], cryptococco- sis [29], mastitis [30], enterocolitis [31 – 33], infec- tious mononucleosis [34], parasitic disease [35], Clostridium perfringens infection [36], osteomyelitis [37 – 42], infection or loosening following arthrop- lasty [43 – 45], fever of unknown origin (FUO) [46 – 48], thrombosis [49 – 51], amyloidosis [52], sarcoidosis [53,54], asthma [55], bronchitis [56], encephalitis [57], costochondritis [58], radiation pneumonitis [59], esophagitis [60,61], pancreatitis [62], thyroiditis [63 – 65], sinusitis [66], myositis [67], mediastinitis [68], gastritis [69], lobular panniculitis [70], dental cavity [71], and inflammation caused by foreign body [72 – 74]. Despite all of these findings, however, FDG-PET has not been fully accepted as an effective way to evaluate infection and inflammation. This 0033-8389/05/$ – see front matter D 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.rcl.2004.07.005 * Corresponding author. E-mail address: abass.alavi@uphs.upenn.edu (A. Alavi). Radiol Clin N Am 43 (2005) 121 – 134