Search

Background: Positron emission tomography (PET) imaging of macrophages using the translocator protein (TSPO) tracer (R)-[11C]PK11195 has shown the promise to image rheumatoid arthritis (RA). To further improve TSPO PET for RA imaging, second generation TSPO tracers [11C]DPA-713 and [18F]DPA-714 have recently been evaluated pre-clinically showing better imaging characteristics. Objective: A clinical proof of concept study to evaluate [11C]DPA-713 and [18F]DPA-714 to visualize arthritis in RA patients. Methods: RA patients (n = 13) with at least two active hand joints were included. PET/CT scans of the hands were obtained after injection of [18F]DPA-714, [11C]DPA-713 and/or (R)-[11C]PK11195 (max. 2 tracers pp). Standardized uptake values (SUVs) and target-to-background (T/B) ratios were determined. Imaging data of the 3 different tracers were compared by pooled post-hoc testing, and by a head to head comparison. Results: Clinically active arthritis was present in 110 hand joints (2–17 pp). Arthritic joints were visualized with both [11C]DPA-713 and [18F]DPA-714. Visual tracer uptake corresponded with clinical signs of arthritis in 80% of the joints. Mean absolute uptake in PET-positive joints was significantly higher for [11C]DPA-713 than for [18F]DPA-714, the latter being not significantly different from (R)-[11C]PK11195 uptake. Background uptake was lower for both DPA tracers compared with that of (R)-[11C]PK11195. Higher absolute uptake and lower background resulted in two-fold higher T/B ratios for [11C]DPA-713. Conclusions: [11C]DPA-713 and [18F]DPA-714 visualize arthritic joints in active RA patients and most optimal arthritis imaging results were obtained for [11C]DPA-713. Second generation TSPO macrophage PET provides new opportunities for both early diagnosis and therapy monitoring of RA. [ABSTRACT FROM AUTHOR]

Introduction. 18F-FDG-PET visualises inflammation. Both atherosclerosis and giant cell arteritis cause vascular inflammation, but distinguishing the two may be difficult. The goal of this study was to assess interobserver agreement and diagnostic accuracy of 18F-FDG-PET for the detection of large artery involvement in giant cell arteritis (GCA). Methods. 31 18F-FDG-PET/CT scans were selected from 2 databases. Four observers assessed vascular wall 18F-FDG uptake, initially without and subsequently with predefined observer criteria (i.e., vascular wall 18F-FDG uptake compared to liver or femoral artery 18F-FDG uptake). External validation was performed by two additional observers. Sensitivity and specificity of 18F-FDG-PET were determined by comparing scan results to a consensus diagnosis. Results. The highest interobserver agreement (kappa: 0.96 in initial study and 0.79 in external validation) was observed when vascular wall 18F-FDG uptake higher than liver uptake was used as a diagnostic criterion, although agreement was also good without predefined criteria (kappa: 0.68 and 0.85). Sensitivity and specificity were comparable for these methods. The criterion of vascular wall 18F-FDG uptake equal to liver 18F-FDG uptake had low specificity. Conclusion. Standardization of image assessment for vascular wall 18F-FDG uptake promotes observer agreement, enables comparative studies, and does not appear to result in loss of diagnostic accuracy compared to nonstandardized assessment. [ABSTRACT FROM AUTHOR]

Objective To determine the current status of positron emission tomography (PET) as a tool for diagnosis and monitoring of peripheral inflammatory arthritis (IA). Methods For conducting this systematic review, the PubMed (Medline), Embase, and Cochrane Library databases were searched until December 31, 2012. Studies of PET for diagnosis and/or therapy monitoring of peripheral IA were included. Data were summarized qualitatively using best evidence synthesis. Results Eighteen articles met our inclusion criteria. The majority of studies were feasibility studies with varying methods applied. All studies demonstrated that PET visualized IA with high sensitivity, corresponding to clinical assessments. PET outcome of clinically active IA also matched that of ultrasound and magnetic resonance imaging. PET differentiates from other modalities by (quantitative) imaging of molecular sites in the synovium. The first studies reporting on the potential clinical applications of PET to image subclinical synovitis in preclinical RA and during therapy have been published. The results are promising, but the number and study populations of these studies are still limited. Conclusion Thus far, a limited number of PET studies addressing IA imaging have been published. The PET modality seems to offer highly sensitive and potentially specific imaging of IA at the (quantitative) molecular level. Clinical application studies for early diagnostics and therapy monitoring are arising, but these topics should be further explored in future studies with larger cohorts. For integration in clinical practice, aspects such as radiation burden and cost-effectiveness should also be taken into account. [ABSTRACT FROM AUTHOR]