Abstract
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Background: Cardiac involvement in sarcoidosis is rare but is an important cause of morbidity and mortality. In the absence of a gold standard investigation, diagnosis of cardiac sarcoidosis is often a clinical dilemma. Myocardial perfusion imaging (MPI) and FDG PET/CT have been used for diagnosis to identify fibrosis and inflammation respectively. However, suppression of physiological FDG uptake in the myocardium is unpredictable and often inadequate. 68Ga-DOTANOC PET/CT is a promising alternative as it targets the somatostatin receptors expressed on inflammatory cells and shows no significant physiological uptake in the myocardium. We evaluated a combination of MPI and 68Ga-DOTANOC PET/CT for diagnosis of cardiac sarcoidosis and compared it with cardiac MRI. Aims and objectives: The aim of the study was to assess role of MPI and 68Ga-DOTANOC PET/CT in patients with clinical suspicion of cardiac sarcoidosis and to compare the results with cardiac MRI. Materials and methods: 20 patients with clinical suspicion of cardiac sarcoidosis were included in the study. Out of the 20 patients, 9 were biopsy proven cases of extra-cardiac sarcoidosis and the rest had a clinical diagnosis. All patients underwent cardiac MRI, MPI with 99mTc-MIBI and 68Ga-DOTANOC PET/CT. Focal myocardial 68Ga-DOTANOC uptake on PET/CT with or without perfusion defect on MPI was considered abnormal. On cardiac MRI, T2 hyperintensity and characteristic pattern of late gadolinium enhancement (LGE) were considered abnormal. Considering cardiac MRI as gold standard, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for the combination of MPI and 68Ga-DOTANOC PET/CT. Results: There were 16 male and 4 female patients (mean age-38.9 years). 5 patients had normal perfusion and no abnormal uptake on 68Ga-DOTANOC PET/CT. 7 patients had normal perfusion and abnormal uptake on 68Ga-DOTANOC PET/CT. 8 patients had perfusion defects and abnormal uptake on 68Ga-DOTANOC PET/CT. Cardiac MRI was suggestive of sarcoidosis in 14 patients. Considering cardiac MRI as gold standard, the combination of 68Ga-DOTANOC PET/CT and MPI had a sensitivity and specificity of 100% and 83.3% respectively and PPV and NPV of 93.3 and 100% respectively. Conclusion: 68Ga-DOTANOC PET/CT in combination with MPI has high sensitivity and specificity for diagnosis of cardiac sarcoidosis and the results are comparable to cardiac MRI.