Imaging the inflammatory activity of sarcoidosis: sensitivity and inter observer agreement of (67)Ga imaging and (18)F-FDG PET.

Aim: The aim of this study was to investigate sensitivity of 67Ga imaging and 18F-FDG PET for sarcoidosis activity and their inter observer variability.

Methods: Thirty-four newly diagnosed, histologically proven sarcoidosis patients were analyzed prospectively. (67)Ga imaging and (18)F-FDG PET were performed, the presence of pulmonary and extra pulmonary lesions was evaluated and inter observer variability of both techniques was assessed.

Results: Overall sensitivity to detect active sarcoidosis was 88% for (67)Ga imaging and 97% for (18)F-FDG PET. Although these results were not significantly different, 18F-FDG PET detected more lesions in the mediastinum (P<0.05), hila (P<0.05), lymph nodes (P<0.001) and extra pulmonary regions in general (P<0.001). Inter observer agreement was poor to moderate for (67)Ga imaging (kappa 0.19-0.59) and good to very good for (18)F-FDG PET (kappa 0.65-1.00).

Conclusion: (18)F-FDG PET is more sensitive than (67)Ga imaging in the assessment of sarcoidosis activity with regard to the mediastinum, hila, lymph nodes and extra pulmonary lesions in general. Furthermore, (18)F-FDG PET demonstrates a very good inter observer agreement in contrast with (67)Ga imaging and (18)F-FDG PET is therefore the nuclear imaging technique of choice in sarcoidosis assessment.