Myocardial imaging with 18F-fluoro-2-deoxyglucose positron emission tomography and magnetic resonance imaging in sarcoidosis

Despite accumulating reports on the clinical value of F-18-fluoro-2-deoxyglucose positron emission tomography (F-18-FDG PET) and magnetic resonance imaging (MRI) in the assessment of cardiac sarcoidosis, no studies have systematically compared the images of these modalities. Twenty-one consecutive patients with suspected cardiac sarcoidosis underwent cardiac examinations that included F-18-FDG PET and MRI. The association of F-18-FDG PET and MRI findings with blood sampling data such as serum angiotensin converting enzyme levels was also evaluated. Eight of 21 patients were diagnosed as having cardiac sarcoidosis according to the Japanese Ministry of Health and Welfare Guidelines for Diagnosing Cardiac Sarcoidosis. Sensitivity and specificity for diagnosing cardiac sarcoidosis were 87.5 and 38.5%, respectively, for F-18-FDG PET, and 75 and 76.9%, respectively, for MRI. When the F-18-FDG PET and MRI images were compared, 16 of 21 patients showed positive findings in one (n=8) or both (n=8) of the two modalities. In eight patients with positive findings on both images, the distribution of the findings differed among all eight cases. The presence of positive findings on F-18-FDG PET was associated with elevated serum angiotensin-converting enzyme levels; this association was not demonstrated on MRI. Both F-18-FDG PET and MRI provided high sensitivity for diagnosing cardiac sarcoidosis in patients with suspected cardiac involvement, but the specificity of F-18-FDG PET was not as high as previously reported. The different distributions of the findings in the two modalities suggest the potential of F-18-FDG PET and MRI in detecting different pathological processes in the heart.