18F-FDG and 68 Ga-FAPI PET/CT for the evaluation of periprosthetic joint infection and aseptic loosening in rabbit models

Prosthetic Joint Infection Research Models in NZW Rabbits: Opportunities for Standardization-A Systematic Review

Prosthetic joint infection (PJI) is a major complication following total arthroplasty. Rising antimicrobial resistance (AMR) to antibiotics will further increase therapeutic insufficiency. New antibacterial technologies are being developed to prevent PJI. In vivo models are still needed to bridge the translational gap to clinical implementation. Though rabbit models have been used most frequently, there is no consensus about methodology and measured outcomes. The PubMed, Scopus, and EMBASE databases were searched for literature on PJI in rabbit models. Data extraction included bias control, experimental design, and outcome measures of the NZW rabbit models in the articles. A total of 60 articles were included in this systematic literature review. The articles were divided into six groups based on the PJI intervention: no intervention used (21%), revision surgery (14%), prevention with only antibiotics (21%), prevention with surface modifications (7%), prevention with coatings (23%), and others (14%). Despite the current availability of guidelines and recommendations regarding experimental design, bias control, and outcome measures, many articles neglect to report on these matters. Ultimately, this analysis aims to assist researchers in determining suitable clinically relevant methodologies and outcome measures for in vivo PJI models using NZW rabbits to test new antimicrobial technologies.

Volume-Based Quantitative Measurement of [18F]AlF-NOTA-FAPI-04 PET/CT Uptake Reflects the Disease Activity of IgG4-Related Disease

BACKGROUND

To investigate the potential utility of quantitative parameters obtained by 18F-fibroblast activation protein inhibitor positron emission tomography/computed tomography ([18F]AlF-NOTA-FAPI-04 PET/CT) in the assessment of organ involvement and disease activity in IgG4-related disease (IgG4-RD).

METHODS

This study enrolled patients who underwent [18F]AlF-NOTA-FAPI-04 PET/CT scans at the Department of Rheumatology, The First Affiliated Hospital, Zhejiang University School of Medicine from August 2021 to August 2022. The PET/CT images of the included patients were re-evaluated by PET center technicians, and the maximal standardized uptake value (SUVmax), metabolic lesion volume (MLV), and total lesion FAPI (TL-FAPI) were used to evaluate the involved organs and tissues that abnormally accumulated [18F]AlF-NOTA-FAPI-04. The clinical and laboratory data of patients are also systematically collected and analyzed.

RESULTS

Among the patients included in this study, 12 patients met the IgG4-RD classification criteria established by the American College of Rheumatology in 2019. Among them, 8 were males and 4 were females, with an average age of 59.3 ± 11.5 years. 50% of IgG4-RD patients were found with more organ involvement on PET/CT than physical examination, ultrasonography, and computed tomography. IgG4 levels (Rho = 0.594, p = 0.042) and IgG4-RI (Rho = 0.647, p = 0.023) were significantly positively correlated with TL-FAPI. After linear regression analysis, only TL-FAPI showed a predictive value of RI (R2 = 0.356, B = 0.008, p = 0.041).

CONCLUSIONS

[18F]AlF-NOTA-FAPI-04 PET/CT is a useful tool for identifying asymptomatic organ involvement and assessing disease activity. The TL-FAPI as an indicator was positively correlated with IgG4-RD disease activity.

Iliopsoas fibrosis after revision of total hip arthroplasty revealed by 68Ga-FAPI PET/CT: a case report

Background

Total hip arthroplasty (THA) is a well-established surgical procedure that has been extensively validated to alleviate pain, enhance joint function, improve the ability to perform daily activities, and enhance overall quality of life. However, this procedure is associated with certain complications, among which skeletal muscle fibrosis is a frequently overlooked but significant complication that can lead to persistent pain. Currently, there is no effective method for diagnosing skeletal muscle fibrosis following total hip arthroplasty.

Case report

We report a 75-year-old male patient who complained of left groin pain after revision total hip arthroplasty. Serological examinations, X-rays, and bone scan results were all normal. However, during the 68Ga-FAPI PET/CT examination, we observed significant radiotracer uptake along the iliopsoas muscle. This abnormal uptake pattern suggested potential biological activity in this specific area. Combined with physical examination, the patient was diagnosed with iliopsoas fibrosis.

Conclusions

The presented images indicated that the uptake pattern was an important indicator for diagnosis, and the prospect of fibroblast activation protein in the diagnosis of skeletal muscle fibrosis has shown certain application value.

Application of Nuclear Medicine Techniques in Musculoskeletal Infection: Current Trends and Future Prospects

Nuclear medicine has become an indispensable discipline in the diagnosis and management of musculoskeletal infections. Radionuclide tests serve as a valuable diagnostic tool for patients suspected of having osteomyelitis, spondylodiscitis, or prosthetic joint infections. The choice of the most suitable imaging modality depends on various factors, including the affected area, potential extra osseous involvement, or the impact of previous bone/joint conditions. This review provides an update on the use of conventional radionuclide imaging tests and recent advancements in fusion imaging scans for the differential diagnosis of musculoskeletal infections. Furthermore, it examines the role of radionuclide scans in monitoring treatment responses and explores current trends in their application. We anticipate that this update will be of significant interest to internists, rheumatologists, radiologists, orthopedic surgeons, rehabilitation physicians, and other specialists involved in musculoskeletal pathology.

FAPI PET/CT Imaging-An Updated Review

Despite revolutionizing the field of oncological imaging, Positron Emission Tomography (PET) with [18F]Fluorodeoxyglucose (FDG) as its workhorse is limited by a lack of specificity and low sensitivity in certain tumor subtypes. Fibroblast activation protein (FAP), a type II transmembrane glycoprotein, is expressed by cancer-associated fibroblasts (CAFs) that form a major component of the tumor stroma. FAP holds the promise to be a pan-cancer target, owing to its selective over-expression in a vast majority of neoplasms, particularly epithelial cancers. Several radiolabeled FAP inhibitors (FAPI) have been developed for molecular imaging and potential theranostic applications. Preliminary data on FAPI PET/CT remains encouraging, with extensive multi-disciplinary clinical research currently underway. This review summarizes the existing literature on FAPI PET/CT imaging with an emphasis on diagnostic applications, comparison with FDG, pitfalls, and future directions.

Diagnostic efficiency of [68 Ga]Ga-DOTA-FAPI-04 in differentiating periprosthetic hip joint infection and aseptic failure

PURPOSE

To assess the efficiency of [68 Ga]Ga-DOTA-FAPI-04 in diagnosing periprosthetic hip joint infection and establish a diagnostic standard of clinical significance based on uptake pattern.

METHODS

[68 Ga]Ga-DOTA-FAPI-04 PET/CT was performed in patients with symptomatic hip arthroplasty from December 2019 to July 2022. The reference standard was based on the 2018 Evidence-Based and Validation Criteria. Two diagnostic criteria, SUVmax and uptake pattern, were used to diagnose PJI. Meanwhile, original data were imported into IKT-snap to draw the view of interest, A.K. was used to extract features of clinical cases, and unsupervised clustering analysis was applied according to the groups.

RESULTS

A total of 103 patients were included, 28 of whom had PJI. The area under the curve of SUVmax was 0.898, which was better than that of all of the serological tests. The cutoff value of SUVmax was 7.53, and the sensitivity and specificity were 100 and 72%, respectively. The sensitivity, specificity and accuracy of the uptake pattern were 100, 93.1 and 95%, respectively. In radiomics analysis, the features of PJI were significantly different from those of aseptic failure.

CONCLUSION

The efficiency of [68 Ga]Ga-DOTA-FAPI-04 PET/CT in diagnosing PJI showed promising results, and the diagnostic criteria of the uptake pattern were more clinically instructive. Radiomics also showed certain application prospects in the field of PJI.

TRIAL REGISTRATION NUMBER

Trial registration: ChiCTR2000041204. Registered 24 September 2019.

Different uptake patterns of 68Ga-FAPI in aseptic loosening and periprosthetic joint infection of hip arthroplasty: A case series and literature review

Background

The diagnosis of a periprosthetic joint infection (PJI) is always a difficult point in research on the surgery of joints. The current diagnostic criteria include a comprehensive analysis of multiple tests; however, there are no effective visual examinations yet that can differentiate between aseptic loosening and the PJI.

Case presentation

This case report describes four patients with symptomatic total hip arthroplasty (THA), two cases of loosening and two cases of infection. Although the four cases were correctly diagnosed by the tissue culture, preoperative tests and pathological examination could not effectively distinguish an infection from a non-infection. Based on a preclinical study and theoretical feasibility, gallium-68 (⁶⁸Ga)-labeled fibroblast activation protein inhibitor positron emission tomography/computed tomography (⁶⁸Ga-FAPI PET/CT) was performed. Through ⁶⁸Ga-FAPI PET/CT scanning, not only were the causes diagnosed correctly but the lesions were also located.

Conclusion

When the lesion is located between the bone and the prosthesis, ⁶⁸Ga-FAPI PET/CT could differentiate aseptic loosening from periprosthetic joint infection (PJI). ⁶⁸Ga-FAPI PET/CT has clear advantages over routine examinations and has a prospective application in detecting PJI.