Characterization of hepatic tumors using [11C]metomidate through positron emission tomography: comparison with [11C]acetate

Background: Using positron emission tomography (PET), we compared two tracers, [C-11]metomidate ([C-11]MTO) and [C-11]acetate ([C-11]ACE), for the characterization of hepatic tumors. Methods: Thirty-three patients underwent PET with [C-11]MTO and [C-11]ACE and magnetic resonance imaging (MRI). Based on the histology of the tumor biopsy, 14 patients had hepatocellular carcinoma (HCC), 9 patients had focal nodular hyperplasia (FNH), and 10 patients had other types of hepatic tumors. Tumor uptake was evaluated by calculating the maximum and mean standardized uptake value and tumor-to-liver ratio. Results: Altogether, 120 hepatic lesions (59 HCC, 18 FNH, 30 metastases of different primaries, 9 adenomas, and 4 regenerating nodules of liver cirrhosis) were detected by MRI. The overall tumor detection rate was slightly higher for [C-11]MTO (39%) than for [C-11]ACE (33%). [C-11]ACE was more sensitive for HCC detection (50% versus 43%, respectively), whereas [C-11]MTO was more sensitive for FNH detection (78% versus 44%, respectively). In HCC patients, the tumor grade correlated with [C-11]ACE, but not with [C-11]MTO. All of the patients with liver metastases, from various primary tumors (n = 10), were negative for both tracers. Conclusions: Due to low sensitivity, [C-11]MTO and [C-11]ACE PET have only limited value in diagnosing hepatic tumors.