Somatostatin receptor imaging in active cardiac sarcoidosis: Would less be enough?

Semiquantitative evaluation of 68Ga-DOTANOC uptake in the normal myocardium: establishment of reference values

BACKGROUND

To ascertain presence of physiological uptake and derive standardized uptake values (SUV) of 68Ga-DOTANOC in normal myocardium and establish reference values.

METHODS AND RESULTS

Dedicated cardiac 68Ga-DOTANOC PET/CT studies of patients referred for evaluation of cardiac sarcoidosis (CS) or myocarditis and found to be normal on visual assessment and on cardiac MRI were analyzed semiquantitatively. The studies were acquired 45-60 minutes after intravenous injection of 111-185 MBq of 68Ga-DOTANOC. Myocardial SUVmax normalized to lean body mass (SUVmax_lbm) values for septum, anterior wall, proximal lateral wall, distal lateral wall, inferior wall, and apical region were 1.12 ± .39, 1.09 ± .42, 1.26 ± .49, 1.16 ± .40, 1.23 ± .39, and 1.05 ± .40, respectively. Myocardial SUVmax_lbm-to-blood pool SUVmean_lbm ratios were calculated for each region and 95th percentile values of these ratios were considered the upper limit of normal. 95th percentile values of myocardial SUVmax_lbm-to-blood pool SUVmean_lbm ratio for the corresponding regions were 1.70, 1.70, 2.00 1.95, 2.05, and 1.70, respectively.

CONCLUSION

There can be physiological uptake of 68Ga-DOTANOC in normal myocardium and the reference values of semiquantitative parameters established in this study may be employed as a corroborative tool for visual assessment in patients undergoing 68Ga-DOTANOC PET/CT for suspected CS or myocarditis.

Potential novel imaging targets of inflammation in cardiac sarcoidosis

Cardiac sarcoidosis (CS) is an inflammatory disease with high morbidity and mortality, with a pathognomonic feature of non-caseating granulomatous inflammation. While 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a well-established modality to image inflammation and diagnose CS, there are limitations to its specificity and reproducibility. Imaging focused on the molecular processes of inflammation including the receptors and cellular microenvironments present in sarcoid granulomas provides opportunities to improve upon FDG-PET imaging for CS. This review will highlight the current limitations of FDG-PET imaging for CS while discussing emerging new nuclear imaging molecular targets for the imaging of cardiac sarcoidosis.