F-18 Fluorodeoxyglucose PET/CT as a Diagnostic Tool in Orbital Inflammatory Disorders

Abstract

Background: In the last decade, FDG-PET/CT has become routine practice in the management of lymphoma or autoimmune diseases. In the current study, we aimed to assess the usefulness of FDG-PET/CT as a potential diagnostic tool for detecting underlying systemic diseases (SD) in patients with orbital in ammatory disorders (OID). Methods: All consecutive patients managed for new-onset OID between 2011 and 2018 in a tertiary referral center for OID, who underwent FDG-PET/CT as part as the etiological diagnostic workup were enrolled. PET-FDG/CT scans were reviewed blindly and were considered as positive for SD detection if they showed lymphadenopathy and/or other visceral lesions with an uptake above blood pool background. We used the standard diagnostic workup (performed in all patients at presentation) as relevant comparator. To quantify the incremental value of FDG-PET/CT over the standard diagnostic workup, the Net Reclassi cation Index (NRI) and Integrated Discrimination Index (IDI) were used. The nal diagnosis was based on international criteria for autoimmune diseases, or histological con rmation for lymphoma, xanthogranuloma, crystal storing histiocytosis (CSH), or idiopathic orbital in ammation syndrome (IOIS).Results: Among the 22 patients enrolled, 14 (63%) had underlying SD (granulomatosis with polyangiitis (GPA), n=1; IgG4-related disease (IgG4-RD), n=5; CSH, n=1; adult onset asthma and periocular xanthogranuloma (AAPOX), n=3; lymphoma, n=4) while the remaining 8 (37%) patients were diagnosed with IOIS. Eleven (50%) patients had a positive FDG-PET/CT. After clinicobiological evaluation, FDG-PET/CT correctly reclassi ed 29% of patients with SD (p=0.04) and 13% with IOIS (p=0.3), corresponding to an elevated NRI of 0.41±0.17 (p=0.03). The IDI test used to evaluate the improvement of FDG-PET/CT for SD detection was 0.38±0.08 (p<0.001). After FDG-PET/CT, probability changes for SD and IOIS were measured at 0.14 and -0.24, respectively (relative gain of 3.04 for IDI). FDG-PET/CT successfully detected asymptomatic lesions in all patients with a nal diagnosis of lymphoma.Conclusion: FDG-PET/CT enabled accurate reclassi cation of more than one quarter of patients with SD, suggesting its potential value for detecting SD (especially extraorbital lymphoma).

Current imaging methods for assessing Graves` orbitopathy activity with particular emphasis on FDG-PET

“…This research offers proof that nuclear imaging might be useful for diagnosing underlying (but undiscovered) systemic disease and for accurate disease staging at diagnosis. The researchers advise undertaking an FDG-PET/CT as a second-line test if the results of the first line of studies are negative (35). Supplementary Figures 1 and 2 present MRI and PET/CT images of a patient with GO treated at our Clinic.…”