Background To assess the role of (18F)FDG-PET/CT imaging in management of patients suspected to have large vessel vasculitis (LVV) with systemic and/or GCA/PMR features with or without history of large vessel vasculitis.

Objectives To analyze the impact of (18F)FDG-PET/CT imaging in suspected large vessel vasculitis and treatment modifications and follow up outcomes after a positive or negative scan.

Methods Retrospective analysis of all (18F)FDG-PET/CT scans performed for suspected large vessel vasculitis at Brighton & Sussex University Hospital between Jan. 2007 to Feb. 2012. Comprehensive database search was conducted to include all patients who had scans done in this period. 56 PET scans were identified. PET scan reports were classified as 1) positive for large vessel vasculitis 2) negative for large vessel vasculitis but showing other findings 3) normal scans. Clinical features, laboratory and imaging investigations data were collected using a standard proforma. The impact of (18F)FDG-PET/CT on management including treatment modifications and follow up outcomes was reviewed.

Results 56 PET/CT scans (F45 age range 28-87; M11 age range 25-75) were performed for suspected large vessel vasculitis. 16 scans (28.6%) were positive for large vessel vasculitis. 4 scans showed high uptake, 5 moderate uptake and 7 low uptake. 8/16 patients had current or past medical history of LVV. Treatment changes were made in14/16 patients. 2 patients with low uptake were not treated. 16 scans (28.6%) were negative for LVV but showed other findings (4 synovitis, 4 bowel/peritoneal, 2 arterial, 2 thyroid, 2 lymph nodes, 1 muscle, 1 bone marrow) changing diagnosis. 24 scans (42.9%) were normal excluding LVV as possible cause. No diagnosis of LVV transpired on follow up in patients who had negative PET scans for vascular uptake. ESR did not correlate significantly with PET findings.

Conclusions (18F)FDG-PET/CT imaging is a valuable tool in the diagnosis of LVV especially in patients with history of LVV with suspected relapse. Positive or negative scans invariably impact management. ESR does not correlate with vascular uptake.

Acknowledgements Dr Sabina Dizdarevic

Consultant Nuclear Medicine Physician

Department of Nuclear Medicine

Brighton & Sussex University Hospital NHS Trust

Disclosure of Interest None Declared