Diagnosis and assessment of the treatment response in a case of giant cell arteritis using (18)F-FDG PET/CT.

A 56-year-old woman complained of a five months history of low-grade fever, headache, cough, weight loss, backache, weakness and muscle pain in the lower extremities with progressive difficulties of gait. Physical examination was normal. Biochemical data showed an erythrocyte sedimentation rate (ESR) of 94mm/h, a C-reactive protein (CRP) of 4.2mg/dl, and a normocytic anemia with hemoglobin of 11.3 g/dl. All other laboratory tests, including thyroid hormones, tumour markers, rheumatoid factor, total complement level, anti-streptolysin O (ASLO), virus serology, antinuclear antibody (ANA), antiproteinase-3, antimyeloperoxidase antibody and angiotensin-converting enzyme (ACE) were negative. Chest X-ray, abdominal ultrasonography, and thoracic and abdominal CTwere performed and reported as normal. Therefore, a 67Ga-citrate scan was requested but planar whole-body views and thoracic SPECT showed no abnormality. In this context, and as giant cell arteritis (GCA) and/or polymyalgia rheumatica was suspected, an 18F-FDG PET/CT scan was requested. 18F-FDGPET/CTwasperformed90minafter intravenous injection of 7 MBq/kg of 18F-FDG. Basal glucose serum level was 91mg/dl. First, a low-doseCT scanwas acquired anddatawereused for attenuation correction and anatomical localization purposes. Following theCT scan, awhole-bodyPET scan including extremities was acquired (2min per bed). The imageswere reconstructed using an iterativeOSEMalgorithm(2 iterations and8 subsets) andaGaussian filter of 5mm. The images obtained revealed a well defined increased 18F-FDG lineal uptake along the walls of the supra-aortic trunks, thoracic andabdominal aorta (Figs. 1A, 2AandB), initial part