There has been a significant increase in the number of joint prosthesis replacements worldwide. Although relatively uncommon, complications can occur with the most serious being an infection. Various radiological and nuclear imaging techniques are available to diagnose prosthetic joint infections (PJI). In this review article, we describe the pathophysiology of PJI, the principles of nuclear medicine imaging and the differences between Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET). The value of nuclear medicine techniques for clinical practice is also discussed.Then we provide an overview of the most often used radionuclide imaging techniques that may be helpful in diagnosing prosthetic joint infection: the 67 Ga-citrate, labelled white blood cells in vitro and in vivo (monoclonal antibodies directed against specific targets on the leukocytes), and 18 F-fluorodeoxyglucose ( 18 F-FDG). We describe their working methods, the pitfalls, and the interpretation criteria. Furthermore, we review recent advances in imaging bacteria, a molecular imaging method that holds promises for the detection of occult infections. We conclude proposing two diagnostic flow-charts, based on data in the literature, that could help the clinicians to choose the best nuclear imaging method when they have a patient with suspicion of or with proven PJI.

Using this protocol, visual analysis had high sensitivity and specificity in the diagnosis of infection. Semiquantitative analysis could be used in doubtful cases, with no cut-off for the percentage increase in radiolabelled WBC over time, as a criterion to define a positive scan.

Purpose: Scintigraphy with radiolabelled autologous white blood cells (WBC) is a widely used method for the detection of sites of infection. In this study we evaluated the role of WBC scintigraphy in the diagnosis and follow-up of patients with suspected soft tissue infection caused by dermal fillers in the face. We compared several qualitative and quantitative interpretation criteria and the results obtained with MRI and high-frequency US (HFUS). Methods: Between 2007 and 2011, ten consecutive patients (all women) aged between 25 and 65 years showing a reaction to dermal fillers were enrolled in the study. In five of these patients WBC scintigraphy was repeated at the end of therapy. Scintigraphy with 99mTc-HMPAO-labelled WBC was performed in each patient acquiring planar and SPECT images at 3 h and 20 h as well as HFUS with Doppler analysis and MRI with Gd-DTPA. The final diagnosis was determined by fine-needle aspiration and microbiological analysis of lesions in eight patients (before therapy in six and after therapy in two) and by clinical data and follow-up (at least 1 year) in seven patients (before therapy in four and after therapy in three). Two patients were treated with steroids, and the others were treated with antibiotics for 3 weeks. Several qualitative and semiquantitative interpretation criteria were applied to define the best strategy for accurate diagnosis of infections, implemented by SPECT images in patients with doubtful planar scans. The WBC scintigraphy results were also compared with the MRI and HFUS results. Results: Sensitivity, specificity and accuracy were respectively 90 %, 100 % and 93.3 % for WBC scintigraphy with qualitative and semiquantitative interpretation of planar images and 100 %, 100 % and 100 % with qualitative analysis of SPECT images. Sensitivity, specificity and accuracy for HFUS were 44 %, 66 % and 50 %, and for MRI were 50 %, 100 % and 67.6 %, respectively. Scans performed after therapy in five patients were negative in three and still positive in two (all true results). Conclusion: In conclusion, scintigraphy with radiolabelled WBC was found to be the most accurate method for diagnosing infection in patients with long-term dermal filler complications, particularly using qualitative analysis of SPECT images. No differences were observed with planar images using either qualitative or semiquantitative analysis. HFUS and MRI may provide additional important information for defining the nature of the filler and for surgery, but are not accurate enough for diagnosing infection. © 2012 Springer-Verlag Berlin Heidelberg

In the field of inflammation imaging, nuclear medicine techniques can be considered as a non-invasive tool to early detect pathophysiological changes in affected tissues. These changes usually occur before clinical onset of symptoms and before the development of anatomical changes, that are commonly detected by radiological procedures. This is particularly important for prognostic purposes, therapy decision making and for therapy follow-up. Here we review the current state-of-the art of nuclear medicine for diagnostic purposes in different conditions characterized by a chronic inflammation, such as vulnerable atherosclerotic plaques, vasculitis, rheumatoid arthritis, Sjogren syndrome, autoimmune thyroid diseases, inflammatory bowel diseases, Coeliac disease, Type 1 diabetes mellitus and other immunological diseases. Overall, we describe several different approaches based on radiolabeled cells, peptides and antibodies or FDG. It emerges the role of PET and of hybrid cameras in particular (SPECT/CT and PET/CT) for diagnosis of these disorders and for therapy decision making and followup.

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