Giant Cell Arteritis: A Systematic Review of the Qualitative and Semiquantitative Methods to Assess Vasculitis with 18F-Fluorodeoxyglucose Positron Emission Tomography

Abstract

Giant cell arteritis (GCA) is the most common vasculitis affecting medium and large vessels. It shows a close clinical association with polymyalgia rheumatica (PMR), a musculoskeletal inflammatory disorder, which is clinically characterized by girdles pain and stiffness. 18F-Fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) is an effective tool for the diagnosis, grading, and follow-up of patients affected by GCA involving the aorta and its proximal branches, but the lack of a standardized method for the assessment of vascular inflammation remains a critical issue, potentially leading to misclassification. In our systematic review, including 19 original articles for a total of 442 GCA patients (with or without PMR symptoms) and 535 healthy controls, we described the different qualitative, semiquantitative and combined methods that have been proposed throughout the literature for assessing the presence and grading the severity of GCA-related vascular inflammation on 18F-FDG PET scans, focusing on the diagnostic performance and examining their respective advantages and limitations. The majority of the included studies adopted qualitative methods of PET image analysis, which are less sensitive but more specific than semiquantitative ones. Among the semiquantitative approaches, the aortic-to-blood pool uptake ratio of the aortic arch seems to be the most accurate method.

The Role of Ultrasound Compared to Biopsy of Temporal Arteries in the Diagnosis and Treatment of Giant Cell Arteritis (TABUL): a diagnostic accuracy and cost-effectiveness study

“…Imaging first emerged in the 1990s as a potential means by which to provide evidence to support a diagnosis of GCA. [8][9][10][11][12][13][14][15] High-resolution magnetic resonance imaging (MRI) of temporal arteries offers a non-invasive technique for investigating suspected GCA, but it is limited by availability and cost. Ultrasound is the most practical and widely used modality.…”

Various forms of ¹⁸F-FDG PET and PET/CT findings in patients with polymyalgia rheumatica

“…Visual methods are more specific than semiquantitative ones, but they have lower sensitivity. The most commonly used semiquantitative method is aorta-to-liver ratio 24 , but a promising alternative is also the aortic-to-blood pool uptake ratio 25 . There is no consensus on the best evaluation method.…”

The prognostic value of baseline 18F-FDG PET/CT in steroid-naïve large-vessel vasculitis: introduction of volume-based parameters

“…Some issues, however, have not been fully analysed. While many papers focused their attention on the diagnostic accuracy of the procedure and its ability to bring about a clinical diagnosis, even though the lack of a standard criterion for positivity (visual analysis of the images, various semi-quantitative parameters) remains an open problem [21][22][23][24][25], the number of works about the prognostic power of the technique is substantially inferior [26][27][28].…”