Combined FDG PET/MRI versus Standard-of-Care Imaging in the Evaluation of Cardiac Sarcoidosis

Purpose: To compare combined cardiac fluorine 18 (F-18) fluorodeoxyglucose (FDG) PET/MRI with standard-of-care evaluation using cardiac MRI, F-18-FDG PET/CT, and SPECT perfusion imaging in suspected cardiac sarcoidosis (CS) with respect to radiation dose, imaging duration, and diagnostic test performance. Materials and Methods: Consecutive patients with suspected CS undergoing clinical evaluation with cardiac F-18-FDG PET/CT and gated rest technetium 99m sestamibi SPECT perfusion imaging were prospectively recruited between November 2017 and May 2021 for parallel assessment with combined cardiac F-18-FDG PET/MRI on the same day (ClinicalTrials.gov identifier, NCT03356756). Total effective radiation dose and imaging duration were compared between approaches (combined cardiac PET/MRI vs separate cardiac MRI, PET/CT, and SPECT). MRI findings were initially interpreted without PET data, and then PET and late gadolinium enhancement images were fused and interpreted together. Final diagnosis of CS was established using Japanese Ministry of Health and Welfare guidelines. Results: Forty participants (mean age, 54 years +/- 14 [SD]; 26 [65%] male participants) were included, 14 (35%) with a final diagnosis of CS. Compared with separate cardiac MRI, PET/CT, and SPECT perfusion imaging, combined cardiac PET/MRI had 52% lower total radiation dose (8.0 mSv +/- 1.2 vs 16.8 mSv +/- 1.6, P < .001) and 43% lower total imaging duration (122 minutes +/- 15 vs 214 minutes +/- 26, P < .001). Combined PET/MRI had the highest area under the curve for diagnosis of CS (0.84) with 96% specificity and 71% sensitivity for colocalized FDG uptake and late gadolinium enhancement in a pattern typical for CS. Conclusion: In the evaluation of suspected CS, combined cardiac F-18-FDG PET/MRI had a lower radiation dose, shorter imaging duration, and higher diagnostic performance compared with standard-of-care imaging.