Comprehensive metabolic and morphologic disease characterization in systemic sclerosis: initial results using combined positron emission tomography and magnetic resonance imaging

BACKGROUND: The aim of this study was to evaluate the role of metabolic and morphologic parameters derived from simultaneous hybrid PET/MRI in correlation to clinical criteria for an image-based characterization of musculoskeletal, esophagus and lymph node involvement in systemic sclerosis (SSc). METHODS: Between November 2013 and May 2015, simultaneous whole-body hybrid PET/MRI was performed in 13 prospectively recruited patients with SSc. A mean dose of 241.3 MBq 2-deoxy-2-[18F]fluoro-D-glucose (FDG) was injected. SUVmean and SUVmax values were measured in the spinal bone marrow, spleen, joints, muscles, fasciae, mediastinal lymph nodes and esophagus. MRI abnormalities were scored as 0 (absent), 1 (moderate) and 2 (marked). In addition, organ and skin involvement were graded with clinical sum score (CSS) and modified Rodnan skin score (mRSS), respectively. RESULTS: Results indicate positive correlations between mRSS and fascial FDG-uptake values (fascia summed SUVmax ρ=0.67; fascia summed SUVmean ρ=0.66) that performed better than the MRI sum score (ρ=0.50). Fascial FDG-uptake is also useful in the differentiation between diffuse and limited SSc. Additionally, FDG-PET detected patients with active mediastinal lymphadenopathy and MRI proved to be useful for the delineation of esophagus involvement. CONCLUSIONS: Fascial FDG-uptake has a strong correlation with mRSS and can discriminate between limited and diffuse SSc. These results and the detection of active lymphadenopathy and esophagus involvement can identify patients with advanced scleroderma. Combined PET/MRI therefore provides complementary information on the complex pathophysiology and may integrate several imaging procedures in one.