significantly more frequent in patients with underlying vasculitis when comparing with healthy individuals.
Other imaging techniques such as Doppler ultrasound had been reported useful in assessing the carotid arteries. Otherwise, fluorodeoxyglucose positron emission tomography (FDG-PET) had also been supported by a Japanese study for its role at initial diagnosis and monitoring of vascular activity in various causes of vascular inflammation [ 8 ]. In this study, with a cut-off standardized uptake value (SUV) at 2.1, the sensitivity and specificity of FDG-PET was 92.6% and
the Rheumatic Diseases 2009 68 1811 1818
 Machado P, Landewé R, Lie E, et al Ankylosing Spondylitis Disease Activity Score (ASDAS): defining cut-off values for disease activity states and improvement scores. Annals of the Rheumatic Diseases 2011;70:47-53.) 10.1136/ard.2010.138594 21068095
Machado P Landewé R Lie E et al Ankylosing Spondylitis Disease Activity Score (ASDAS): defining cut-off values for disease activity states and improvement scores Annals of the Rheumatic Diseases 2011 70 47 53
to the emission data to obtain the attenuation-corrected image. Apart from improving the image quality, this correction process is also essential for quantification that generates standardized uptake values (SUV). Abnormal PET activity should also be interpreted by comparing with background organ activity such as liver. There are slight variations among different centers because of different FDG activity used, different injection time, different size and site of the lesion(s) under investigation [ 2 ]. In general, the cut-off of SUV of >2.5 (g/ml) would be regarded