Background When faced with a painful knee replacement, ruling out infection is mandatory to set the correct therapeutic approach. However, it is not always easy, especially in subclinical/chronic infections. A multidisciplinary approach is necessary to assess in the most correct way each case of suspected periprosthetic knee joint infection. This review explores the role of nuclear medicine investigations in the management of periprosthetic knee infections and their proper use within a multidisciplinary pathway. Methods A PubMed search was conducted selecting studies from the past 10 years. Results Triphasic bone scintigraphy has high sensitivity (93%) but poor specificity (56%) for periprosthetic joint infections of the knee, with a high negative predictive value (NPV), ranging from 96% to 100%. Consequently, a negative bone scan is useful in ruling out infection. In contrast, radiolabeled leukocyte scintigraphy is characterized by a sensitivity of 85.7-93%, specificity of 93.6-100%, diagnostic accuracy of 92.6-98%, NPV of 93-97.8%, and positive predictive value (PPV) of 66.7-100%. By adding a tomographic acquisition with hybrid single-photon emission computed tomography combined with computed tomography technique (SPECT/CT), the diagnostic accuracy increases. Because 18F-fluorodeoxyglucose (FDG) accumulates at both sites of inflammation and infection, FDG positron emission tomography (PET/CT) shows low specificity. Conclusions A common decision-making process in the diagnosis of periprosthetic joint infection is not yet validated and multidisciplinary integration is mandatory. In this context, nuclear medicine can contribute decisively.
A 76-year-old man, who experienced prostate cancer biochemical relapse after 12 years from radical prostatectomy, underwent abdominal CT scan for restaging purposes, negative for metastases, and then 11C-choline PET/CT. The only finding was an area of focal uptake of radiotracer between the intestinal loops and the abdominal wall; after resection, the lesion demonstrated to be a metastasis from hepatocellular carcinoma (HCC), for which the patient had undergone liver resection 2 years earlier. This case proves that abnormal foci of 11C-choline uptake in the peritoneum in HCC patients have to be kept in mind as possible sites of HCC-metastases.
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