Potential usefulness of 68Ga-citrate PET/CT in detecting infected lower limb prostheses.

BACKGROUND: Prosthetic joint infections may lead to failures of total joint arthroplasty. Radionuclide imaging can play a diagnostic role in identifying such infections, which require two-stage exchange arthroplasty (instead of simple revision surgery performed in non-infected cases). Although 18F-FDG PET/CT has emerged as a novel diagnostic tool in this setting, the clinical usefulness of 68Ga-citrate PET/CT has not been previously investigated. This single-center prospective study was designed to address this issue. METHODS: Between January 2016 and October 2017, we examined 34 patients with clinically proven or suspected prosthetic hip/knee joint infections scheduled to undergo surgery. All patients underwent 68Ga-citrate PET/CT scans and sequential 18F-FDG PET/CT imaging for comparative purposes. Intraoperative findings and the results of microbiological analyses of surgical specimens served as gold standard. The diagnostic results were examined according to (1) image interpretation based on radiotracer uptake patterns and (2) quantitative analysis using volumes of interest (VOIs) to calculate standard uptake values (SUVs) and metabolic volumes (MVs). RESULTS: A total of 26 (76%) patients were diagnosed as having infections. Based on radiotracer uptake pattern criteria, the sensitivity, specificity, and accuracy of 68Ga-citrate PET/CT and 18F-FDG PET/CT were 92%, 88%, and 91% and 100%, 38%, and 85%, respectively. MV was significantly higher in the infected group when 68Ga-citrate PET/CT was used (422.45 vs. 303.65 cm3, p = 0.027), whereas no significant differences were observed on 18F-FDG PET/CT. According to receiver operating characteristic (ROC) curve analysis, a cut-off value of 370.86 for MV resulted in a sensitivity of 61.5% and a specificity of 87.5% (area under curve: 0.75, 95% confidence interval: 0.57-0.88, p = 0.035). CONCLUSIONS: Subject to future confirmation, our data provide preliminary evidence that 68Ga-citrate PET/CT may have a complimentary role to 18F-FDG PET/CT in detecting prosthetic joint infections, being characterized by a higher specificity and the possibility to discriminate between an infectious condition and sterile inflammation. TRIAL REGISTRATION: This prospective study was registered at clinicaltrials.gov (registration number: NCT02855190 ).

C-reactive protein levels can predict positive 18F-FDG PET/CT findings that lead to management changes in patients with bacteremia.

BACKGROUND/PURPOSE: Bacteremia portends high rates of morbidity and mortality. Although 18F-fluorodeoxyglucose positron emission tomography and computed tomography (18F-FDG PET/CT) imaging has clinical value in assessing fever of unknown origin, its usefulness in bacteremia has not been entirely elucidated. We therefore designed the current single-center retrospective study to investigate 1) the clinical value of 18F-FDG PET/CT imaging in assessing bacteremia and 2) the association between laboratory data and imaging findings. METHODS: We examined 102 patients with bacteremia who had undergone 18F-FDG PET/CT imaging. The patients' clinical and laboratory data were reviewed and analyzed in relation to 18F-FDG PET/CT findings. Patients showing positive results underwent quantitative measurements of 18F-FDG uptake. RESULTS: Positive 18F-FDG PET/CT findings were identified in 74 (72.5%) patients, and 40 (54.1%) underwent modified treatment or management because of the imaging results (p = 0.003). Positive 18F-FDG PET/CT findings were significantly associated with higher white blood cell (WBC) counts and C-reactive protein (CRP) levels (p = 0.012 and < 0.001, respectively). Notably, CRP levels accurately predicted (area under curve = 0.752; p < 0.001) positive 18F-FDG PET/CT findings (optimal cut-off point: 54.025 mg/L). CONCLUSION: A majority (54.1%, n = 40) of the patients with positive 18F-FDG PET/CT results underwent treatment modifications; they accounted for most cases (87%) of management changes in our cohort. Leukocytosis and increased CRP levels are significantly associated with positive 18F-FDG PET/CT findings in patients with bacteremia. CRP levels >54.025 mg/L were accurate predictors of positive 18F-FDG PET/CT results.

Clinical utility of FDG PET/CT in acute complicated pyelonephritis-results from an observational study.

BACKGROUND: Acute complicated pyelonephritis (ACP) is an upper urinary tract infection associated with coexisting urinary tract abnormalities or medical conditions that could predispose to serious outcomes or treatment failures. Although CT and magnetic resonance imaging (MRI) are frequently used in patients with ACP, the clinical value of 18F-fluorodeoxyglucose positron emission tomography and computed tomography (FDG PET/CT) has not been systematically investigated. This single-center retrospective study was designed to evaluate the potential usefulness of FDG PET/CT in patients with ACP. METHODS: Thirty-one adult patients with ACP who underwent FDG PET/CT were examined. FDG PET/CT imaging characteristics, including tracer uptake patterns, kidney volumes, and extrarenal imaging findings, were reviewed in combination with clinical data and conventional imaging results. RESULTS: Of the 31 patients, 19 (61%) showed focal FDG uptake. The remaining 12 study participants showed a diffuse FDG uptake pattern. After volumetric approximation, the affected kidneys were found to be significantly enlarged. Patients who showed a focal uptake pattern had a higher frequency of abscess formation requiring drainage. ACP patients showing diffuse tracer uptake patterns had a more benign clinical course. Seven patients had suspected extrarenal coinfections, and FDG PET/CT successfully confirmed the clinical suspicion in five cases. FDG PET/CT was as sensitive as CT in identifying the six patients (19%) who developed abscesses. Notably, FDG PET/CT findings caused a modification to the initial antibiotic regimen in nine patients (29%). CONCLUSIONS: FDG PET/CT may be clinically useful in the assessment of patients with ACP who have a progressive disease course.