TY - JOUR T1 - Positron Emission Tomography/Computed Tomography for the Diagnosis and Assessment of Giant Cell Arteritis: When to Consider It and Why JF - The Journal of Rheumatology JO - J Rheumatol SP - 1909 LP - 1911 DO - 10.3899/jrheum.120171 VL - 39 IS - 10 AU - ALISON CLIFFORD AU - STEVEN BURRELL AU - JOHN G. HANLY Y1 - 2012/10/01 UR - http://www.jrheum.org/content/39/10/1909.abstract N2 - Large-vessel involvement is now well recognized in patients with giant cell arteritis (GCA). While exact numbers vary, a recent study demonstrated that up to 67.5% of patients with biopsy-proven GCA have large-vessel disease at the time of diagnosis1. On occasion, large-vessel arteritis may occur in isolation, without classical features such as headache and scalp tenderness, making a clinical diagnosis difficult2. Recognition, however, remains important, as mortality in this subset of patients is significantly increased3.While temporal artery biopsy remains the diagnostic gold standard in GCA, it may be falsely negative in 42% of patients with isolated large artery disease2. In such cases, imaging studies are necessary to confirm large-vessel vasculitis. Angiography is suboptimal because of its invasive nature, risks of contrast allergy and nephropathy, and ability to detect only late anatomical changes such as stenosis or aneurysm. Positron emission tomography/computed tomography (PET/CT) is an alternative, offering the ability to detect both structural lesions and active inflammation.When inflammatory cells become activated, they undergo a “respiratory burst” and metabolize large amounts of glucose4. (18F) fluorodeoxyglucose (FDG) PET is a nuclear medicine scan that uses a glucose analog labeled with radioactive fluorine-18, which is taken into cells through the glut-1-transporter. This tracer mimics the distribution of glucose, thereby identifying conditions with high glucose metabolism, such as malignancy, infection, and inflammation5. Current PET scans are often combined with a low-dose CT scan for enhanced anatomical localization of isotope. While used most commonly for oncologic detection and staging, PET/CT is gaining popularity for use in a number of inflammatory diseases, and has notable advantages for the diagnosis of large-vessel arteritis.PET/CT identifies active inflammation within the arterial wall, potentially leading to an earlier diagnosis of GCA. Studies of small numbers of … Address correspondence to Dr. J.G. Hanly, Division of Rheumatology, Nova Scotia Rehabilitation Centre (2nd Floor), 1341 Summer Street, Halifax, Nova Scotia B3H 4K4, Canada. E-mail: john.hanly{at}cdha.nshealth.ca ER -