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Background: This study evaluated, as a snapshot, the variability in quantification and image quality (IQ) of the clinically utilized PET [18F]FDG whole-body protocols in Finland using a NEMA/IEC IQ phantom permanently filled with 68Ge. Methods: The phantom was imaged on 14 PET-CT scanners, including a variety of models from two major vendors. The variability of the recovery coefficients (RCmax, RCmean and RCpeak) of the hot spheres as well as percent background variability (PBV), coefficient of variation of the background (COVBG) and accuracy of corrections (AOC) were studied using images from clinical and standardized protocols with 20 repeated measurements. The ranges of the RCs were also compared to the limits of the EARL 18F standards 2 accreditation (EARL2). The impact of image noise on these parameters was studied using averaged images (AVIs). Results: The largest variability in RC values of the routine protocols was found for the RCmax with a range of 68% and with 10% intra-scanner variability, decreasing to 36% when excluding protocols with suspected cross-calibration failure or without point-spread-function (PSF) correction. The RC ranges of individual hot spheres in routine or standardized protocols or AVIs fulfilled the EARL2 ranges with two minor exceptions, but fulfilling the exact EARL2 limits for all hot spheres was variable. RCpeak was less dependent on averaging and reconstruction parameters than RCmax and RCmean. The PBV, COVBG and AOC varied between 2.3–11.8%, 9.6–17.8% and 4.8–32.0%, respectively, for the routine protocols. The RC ranges, PBV and COVBG were decreased when using AVIs. With AOC, when excluding routine protocols without PSF correction, the maximum value dropped to 15.5%. Conclusion: The maximum variability of the RC values for the [18F]FDG whole-body protocols was about 60%. The RC ranges of properly cross-calibrated scanners with PSF correction fitted to the EARL2 RC ranges for individual sphere sizes, but fulfilling the exact RC limits would have needed further optimization. RCpeak was the most robust RC measure. Besides COVBG, also RCs and PVB were sensitive to image noise. [ABSTRACT FROM AUTHOR]

Summary: Sjögren's syndrome (SS) is a common autoimmune disease targeting salivary and lacrimal glands. It is strongly female‐dominant, characterized by low oestrogen levels combined with a local intracrine dihydrotestosterone defect. We hypothesized that these hormonal deficits lead to increased apoptosis of the epithelial cells and plasmacytoid dendritic cell (pDC)‐mediated proinflammatory host responses. Expression of Toll‐like receptors (TLRs)‐7 and ‐9 and cytokine profiles was studied in pDCs treated with apoptotic particles collected in consecutive centrifugation steps of media from apoptotic cells. Expression and localization of SS autoantigens in these particles was also analysed. Furthermore, the effects of sex steroids were studied in pDCs cultured with several concentrations of dihydrotestosterone and 17‐β‐oestradiol, and in saliva of patient treated with dehydroepiandrosterone. Apoptosis of the epithelial cells led to cleavage and translocation of SS‐autoantigens, α‐fodrin and SS‐A, into apoptotic particles. The apoptosis‐induced apoptotic particles also contained another SS‐autoantigen, hy1‐RNA. These particles were internalized by pDCs in a size‐dependent manner and affected TLR‐7 and ‐9 expression and the production of proinflammatory cytokines. The analysed androgens protected cells from apoptosis, influenced redistribution of autoantigens and diminished the apoptotic particle‐stimulated increase of the TLRs in pDCs. Our findings suggest that the formation of apoptotic particles may play a role in loss of immune tolerance, manifested by production of autoantibodies and the onset of autoinflammation in SS. [ABSTRACT FROM AUTHOR]