Supplement Article |
OP22. FDG-PET SCANNING
Cardiovascular Medicine Unit, The Eric Bywaters Centre, Imperial College London, Hammersmith Hospital, London, UK
The large vessel vasculitides giant cell arteritis (GCA) and Takayasu's arteritis are associated with significant morbidity and mortality and may be difficult to manage. In GCA, a classical presentation is easily identified and may be confirmed by a temporal artery biopsy. However, up to 25% of patients present non-specifically with systemic signs and symptoms such as malaise, arthralgia, night sweats and weight loss resulting in a significant diagnostic challenge, a problem that is also encountered in the early pre-occlusive phase of Takayasu's. Moreover, it is now well recognised that vascular inflammation in GCA and Takayasu's may persist, although the patient has achieved remission by clinical and biochemical criteria.
This has led to interest in novel imaging techniques as an aid to diagnosis and disease activity monitoring in large vessel vasculitides. X-ray angiography is the current "gold-standard" investigation for the diagnosis and follow-up of patients with Takayasu's. However, it has limitations inherent to an invasive procedure. Furthermore, it is unreliable in the diagnosis of the early (potentially reversible) inflammatory phase as it only identifies late, fixed changes in lumen diameter. Thus recent studies have focused on non-invasive methods such as Magnetic Resonance (mr) imaging and 18F-Fluorodeoxyglucose Positron Emission Tomography (FDG-PET). 18F-FDG is deoxyglucose labelled to Fluorine-18, a positron emitting radionuclide that identifies areas of high glucose metabolic activity. High levels of glucose metabolism are typically seen in the myocardium and brain but also in malignant tissue and at sites of inflammation.
Recent studies using FDG-PET scanning have demonstrated large and medium vessel involvement in GCA and polymyalgia rheumatica with 98% specificity. Furthermore, FDG-PET has revealed the diagnosis in patients with an atypical presentation. Likewise, a number of groups have shown that FDG-PET and MR imaging (contrast-enhanced and/or angiography) provides useful information in the management of Takayasus's arteritis. Such techniques may allow earlier diagnosis, prediction of relapse and more accurate assessment of response to treatment than conventional clinical assessment and/or intra-arterial angiography. The data to date and prospects for the future use of 18F-FDG-PET scanning in the management of large vessel vasculitides will be reviewed.