The researches find that the Diagnosis of large vessel vasculitis (LVV) and evaluation of its inflammatory activity can be challenging. Our aim was to investigate the value of hybrid positron-emission tomography/magnetic resonance imaging (PET/MRI) in LVV. Therefore All consecutive patients with LVV from the Department of Internal Medicine who underwent PET/MRI were included. But Three PET/MRI patterns are define: (i) “inflammatory,” with positive PET (>liver uptake) and abnormal MRI (stenosis and/or wall thickening); (ii) “fibrous”, negative PET (≤liver uptake) and abnormal MRI; and (iii) “normal”.
PET/MRI In Large-Vessel
Thirteen patients (10 female; median age: 67-years [range: 23–87]) underwent 18 PET/MRI scans. PET/MRI is perform at diagnosis (n = 4), at relapse (n = 7), or during remission (n = 7). Therefore Among the 18 scans, eight (44%) showed an inflammatory pattern and three (17%) a fibrous pattern; the other seven were normal. The distribution of the three patterns did not differ between patients with Takayasu arteritis (TA, n = 10 scans) and those with giant cell arteritis (GCA, n = 8 scans).
PET/MRI findings were normal in 2/10 (20%) TA scans vs. 5/8 (62%) GCA scans (p = 0.3). Median SUVmax was 4.7 [2.1–8.6] vs. 2 [1.8–2.6] in patients with active disease vs. remission, respectively (p = 0.003). Because PET/MRI is a new hybrid imaging modality allowing comprehensive and multimodal analysis of vascular wall inflammation and the vascular lumen. Therefore This technique offers promising perspectives for the diagnosis and monitoring of LVV.
Diagnosis and monitoring of LVV
Large-vessel vasculitis (LVV) is define as a vasculitis affecting large arteries of which giant cell arteritis (GCA) and Takayasu’s arteritis (TA) represent the two main forms. LVV is characterized by arteritis of the aorta and its main branches which can lead to stenosis and aneurysms. The diagnosis of GCA can be challenging, particularly in patients with symptoms consistent with GCA but negative temporal artery biopsy (TAB). In these patients, it is necessary to demonstrate arterial involvement in order to confirm the diagnosis of GCA.
In TA, the assessment of disease activity can be challenging and positron-emission tomography (PET)-imaging can be useful to distinguish fibrotic stenosis from active arterial lesions. Several studies have shown good sensitivity of fluorine-18-fluorodeoxyglucose (FDG)-PET/computed tomography (CT) for the diagnosis of arterial involvement in LVV, with a sensitivity around 89.5% for GCA and 87% for TA. In a recent double-blinded study of 64 newly suspected GCA, the sensitivity and specificity of PET/CT were 92% and 85% respectively compared with TAB; with high negative predictive valu.
In TA, a recent study in twenty-six patients who underwent graft surgery have shows that significant 18F- FDG uptake that is confined to arterial graft sites does not reflect clinically relevant disease activity or progressio. But Available evidence supports the use of PET/magnetic resonance imaging (MRI) on clinic routine and research; with a strong focus on oncology. But Very few studies have focused on FDG-PET/MRI in LVV. But Among 12 patients who underwent PET/MRI, maximum standardized uptake value (SUVmax) and visual scores did not differ between PET/MRI and PET/CT.