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Background: Metabolic imaging is routinely used to demonstrate aortitis in patients with giant-cell arteritis. We aimed to investigate the preclinical model of aortitis in BALB/c IL1rn−/− mice using [18F]fluorodeoxyglucose ([18F]FDG) positron emission tomography–magnetic resonance (PET-MR), gamma counting and immunostaining. We used 15 first-generation specific and opportunistic pathogen-free (SOPF) 9-week-old IL1rn−/− mice, 15 wild-type BALB/cAnN mice and 5 s-generation specific pathogen-free (SPF) 9-week-old IL1rn−/−. Aortic [18F]FDG uptake was assessed as the target-to-background ratio (TBR) using time-of-flight MR angiography as vascular landmarks. Results: [18F]FDG uptake measured by PET or gamma counting was similar in the first-generation SOPF IL1rn−/− mice and the wild-type group (p > 0.05). However, the first-generation IL1rn−/− mice exhibited more interleukin-1β (p = 0.021)- and interleukin-6 (p = 0.019)-positive cells within the abdominal aorta than the wild-type mice. In addition, the second-generation SPF group exhibited significantly higher TBR (p = 0.0068) than the wild-type mice on the descending thoracic aorta, unlike the first-generation SOPF IL1rn−/− mice. Conclusions: In addition to the involvement of interleukin-1β and -6 in IL1rn−/− mouse aortitis, this study seems to validate [18F]FDG PET-MR as a useful tool for noninvasive monitoring of aortitis in this preclinical model. [ABSTRACT FROM AUTHOR]

Background: The aim of this study was to investigate the quantification performance of a 360° CZT camera for 177Lu-based treatment monitoring. Methods: Three phantoms with known 177Lu activity concentrations were acquired: (1) a uniform cylindrical phantom for calibration, (2) a NEMA IEC body phantom for analysis of different-sized spheres to optimise quantification parameters and (3) a phantom containing two large vials simulating organs at risk for tests. Four sets of reconstruction parameters were tested: (1) Scatter, (2) Scatter and Point Spread Function Recovery (PSFR), (3) PSFR only and (4) Penalised likelihood option and Scatter, varying the number of updates (iterations × subsets) with CT-based attenuation correction only. For each, activity concentration (ARC) and contrast recovery coefficients (CRC) were estimated as well as root mean square. Visualisation and quantification parameters were applied to reconstructed patient image data. Results: Optimised quantification parameters were determined to be: CT-based attenuation correction, scatter correction, 12 iterations, 8 subsets and no filter. ARC, CRC and RMS results were dependant on the methodology used for calculations. Two different reconstruction parameters were recommended for visualisation and for quantification. 3D whole-body SPECT images were acquired and reconstructed for 177Lu-PSMA patients in 2–3 times faster than the time taken for a conventional gamma camera. Conclusion: Quantification of whole-body 3D images of patients treated with 177Lu-PSMA is feasible and an optimised set of parameters has been determined. This camera greatly reduces procedure time for whole-body SPECT. [ABSTRACT FROM AUTHOR]