FDG PET/CT for the diagnosis of cranial and extra-cranial giant cell arteritis

ABSTRACT

Objectives: During the COVID-19 lockdown, temporal artery biopsy (TAB) procedures were not available at ourinstitution for the diagnosis of giant cell arteritis (GCA). For the evaluation of large vessel vasculitis, 18F-fluorodeoxyglucose PET/CT (FDG PET/CT) has good diagnostic performance (pooled sensitivity of 90% andspecificity of 98%). Recently, limited data has been reported that cranial artery inflammation can be detected onnewer generation non-digital PET/CT scanner. With such advancements, it has been suggested that FDG PET/CTmay be able to replace TAB. We hypothesized that digital FDG PET/CT can be used for the diagnosis of GCAthrough the integrated assessment of cranial and extracranial artery inflammation. Methods: We report data from the use of our GE Discovery MI digital PET/CT for the diagnosis of GCA as analternative to TAB during the COVID-19 lockdown. Subjects were included if they were referred for FDG PET/CT forclinically suspected GCA. Exclusion criteria included corticosteroid therapy > 3 days prior to PET/CT or history of known vasculitis. 185-370 MBq of FDG was injected intravenously and imaging acquired 60-90 minutes later.Images were interpreted by two expert readers and a consensus was obtained for every case. Results: Fifteen (9 women, 5 men) subjects were included in the analysis. The mean age was 72 years, mean CRP67.9 mg/L (normal 0-10 mg/L), and mean ESR 56.9 mm/h (normal 2-39 mm/h). Seven subjects were scanned within3 days of corticosteroid initiation and the other 8 had not received corticosteroids. Four of 15 subjects (27%) werediagnosed with GCA by PET with abnormal cranial or large vessel artery uptake (2 subjects with cranial uptakealone and 2 with both cranial and extracranial uptake), and 3 had evidence of PMR on PET without vasculitis. Inthose diagnosed with GCA by PET, vascular inflammation was visualized in the temporal arteries in all 4, maxillaryand occipital arteries in 3 subjects (Fig.1). Alternate diagnoses explaining the clinical presentation were made in 5 of8 remaining subjects (63%) including subacute thyroiditis, active sinusitis, metastatic malignancy and masticatorspace malignancy. During a follow-up period averaging 58 days (range 22 to 94 days), good response to prednisonewas seen in the patients diagnosed with GCA by PET/CT and no evidence of GCA in the remaining non-GCApatients. Conclusions: In conclusion, digital FDG PET/CT appears promising for the diagnosis of GCA through its enhancedsensitivity and resolution to detect small cranial artery inflammation. Further prospective studies comparing digitalFDG PET/CT with current GCA diagnostic modalities is warranted. (Figure Presented).