Imaging of inflamed arteries in giant cell arteritis and inflamed joints in rheumatoid arthritis with a PET/CT scan.

Prior treatment

• Giant cell arteritis - Age ≤ 50 years - Use of oral, intravenous or intramuscular glucocorticoids within 4 weeks prior to inclusion. - Use of disease-modifying antirheumatic drugs (DMARD) within 3 months prior to inclusion. - Treatment with any investigational drug within 3 months prior to inclusion. - Known pregnancy or breast feeding - Research-related radiation exposure (cumulative ≥5 mSv) in the year before inclusion. - Urinary or faecal incontinence Rheumatoid arthritis A potential subject who meets any of the following criteria will be excluded from participation in this study: - Age < 30 years - Use of intra-articular, intramuscular or intravenous corticosteroids within 4 weeks prior to inclusie - Treatment with any investigational drug within the previous 3 months - Known pregnancy or breast feeding - Research related radiation exposure (cumulative ≥5 mSv) in the year before inclusion - Urinary or faecal incontinence

• Giant cell arteritis: - Age > 50 years - Erythrocyte sedimentation rate (ESR) ≥50 mm/hr or C-reactive protein (CRP) ≥ 10 mg/L - Clinical symptoms of GCA present at time of inclusion: • Large vessel GCA (at least one of the following): constitutional symptoms (fatigue, fever, weight loss, and/or night sweats), limb claudication, or symptoms of polymyalgia rheumatica (i.e. shoulder and/or hip girdle pain associated with morning stiffness) • Cranial GCA (at least one of the following): new-onset localized headache, scalp tenderness, temporal artery abnormality (thickening, tenderness, and/or decreased pulsation), ischemia-related vision loss, stroke, transient ischemic attack, jaw or tongue claudication (pain upon mastication). - Imaging findings or temporal artery biopsy findings consistent with GCA at the time of inclusion • Large vessel GCA as suggested by ultrasonography or FDG-PET/CT • Cranial GCA as suggested by ultrasonography FDG-PET/CT or temporal artery biopsy and confirmed by temporal artery biopsy - Patients must be able to adhere to the study appointments and other protocol requirements. - Patients must be capable of giving informed consent and the consent must have been obtained prior to the study related procedures. Rheumatoid arthritis - Patients must be at least 30 years of age - Diagnosis of rheumatoid arthritis according to the 2010 ACR/EULAR Rheumatoid Arthritis classification criteria. - Patients with clinically active disease as assessed by a physician; with arthritis in at least one wrist, knee or ankle joint and have a clinical indication to initiate or escalate treatment - Treatment with disease modifying anti-rheumatic drugs (DMARDS) and oral corticosteroid up to 10 mg daily is allowed, provided that there is a stable dose for at least 4 weeks prior to inclusion - Non-steroidal anti-inflammatory drugs (NSAID) is permitted, provided that there is a stable dose for at least 4 weeks prior to inclusion - Patients must be able to adhere to the study appointments and other protocol requirements - Patients must be capable of giving informed consent and the consent must have been obtained prior to the study related procedures.