Total-Body ¹⁸F-FDG PET/CT in Autoimmune Inflammatory Arthritis at Ultra-Low Dose: Initial Observations

Abstract

Autoimmune inflammatory arthritides (AIA), such as psoriatic arthritis and rheumatoid arthritis, are chronic systemic conditions that affect multiple joints of the body. Recently, total-body (TB) PET/CT scanners exhibiting superior technical characteristics (total-body coverage, geometric sensitivity) that could benefit AIA evaluation, compared with conventional PET/CT systems, have become available. The objectives of this work were to assess the performance of an ultralow-dose, 18 F-FDG TB PET/CT acquisition protocol for evaluating systemic joint involvement in AIA and to report the association of TB PET/CT measures with joint-by-joint rheumatologic examination and standardized rheumatologic outcome measures. Methods: Thirty participants (24 with AIA and 6 with osteoarthritis) were prospectively enrolled in this single-center, observational study. All participants underwent a TB PET/CT scan for 20 min starting at 40 min after intravenous injection of 78.1 6 4.7 MBq of 18 F-FDG. Qualitative and quantitative evaluation of 18 F-FDG uptake and joint involvement were performed from the resulting images and compared with the rheumatologic assessments. Results: TB PET/CT enabled the visualization of 18 F-FDG uptake at joints of the entire body, including those of the hands and feet, in a single bed position, and in the same phase of radiotracer uptake. A range of pathologies consistent with AIA (and non-AIA in the osteoarthritis group) were visualized, and the feasibility of extracting PET measures from joints examined by rheumatologic assessments was demonstrated. Of 1,997 evaluable joints, there was concordance between TB PET qualitative assessments and joint-byjoint rheumatologic evaluation in the AIA and non-AIA cohorts for 69.9% and 91.1% joints, respectively, and an additional 20.1% and 8.8% joints, respectively, deemed negative on rheumatologic examination showed PET positivity. On the other hand, 10.0% and 0% joints in the AIA and non-AIA cohorts, respectively, were positive on rheumatologic evaluation but negative on TB PET. Quantitative measures from TB PET in the AIA cohort demonstrated a moderateto-strong correlation (Spearman r 5 0.53-0.70, P , 0.05) with the rheumatologic outcome measures. Conclusion: Systemic joint evaluation in AIA (and non-AIA) is feasible with a TB PET/CT system and an ultra-low-dose protocol. Our results provide the foundation for future larger studies to evaluate the possible improvements in AIA joint assessment via the TB PET/CT technology.

EXPLORing Arthritis with Total-body Positron Emission Tomography

“…From the experience of nuclear medicine physicians at our institution when assessing total-body PET scans of clinical oncology patients, 18 F-FDG patterns consistent with OA are frequently encountered. Anecdotally, we have also seen elevated uptake in joints presenting with anatomical anomalies on CT consistent with OA when using the radiotracer 18 F-fluciclovine, 78 used primarily for prostate cancer imaging. However, dedicated clinical diagnosis or evaluation for OA was not available in these cases, and a prospective study is needed to establish the significance of the imaging measures.…”

“…[59][60][61] We evaluated three consolidated PET measures over the 28 joints, the total positive joint count, average PET positivity scores, and average maximum standardized uptake value (SUVmax). 62 The Spearman rank correlations of these scores with the DAS28 were in the moderate category, ranging from 0.40 to 0.60 (p < 0.05). We conducted dynamic PET scans in a subset of study participants, where we captured imaging data over 60 minutes following 18 F-FDG injection.…”

[18F] FDG uptake in patients with spondyloarthritis: correlation with serum inflammatory biomarker levels

“…Takata et al demonstrated that SUVmax in lesions correlated with PsA DAS, including the Psoriasis Area and Severity Index and the DAS28 [ 26 ]. Abdelhafez et al also reported that in PsA patients, FDG PET metrics showed a significant correlation with DAPSA [ 13 ]. These findings highlight the possible utility of FDG PET for the assessment of disease activity in PsA patients.…”

“…Therefore, FDG PET may be more advantageous than MRI for assessment of SpA. In fact, previous studies using FDG PET on SpA demonstrated its utility in detecting lesions, and assessment of FDG uptake distribution was useful for differentiation from other rheumatic diseases [ 7 – 13 ]. Moreover, whole-body FDG PET scanning can detect other coexisting diseases.…”

Update on Imaging of Inflammatory Arthritis and Related Disorders

“…It is obviously even more challenging when the query for scanning is rather nonspecific, such as cause of persisting inflammatory syndrome, without obvious rheumatologic signs. In this setting, total-body scanning in a relatively short time and lack of time gap between the PET and CT component would be extremely useful as demonstrated by Abdelhafez et al 100 In dedicated patients,…”