Comparison of system A and system L amino acid transports in human pancreas with C-11 MeAIB and C-11 MET PET study

Objectives To clarify the difference between system A and L amino acid transport imaging in clinical PET, we analyze the pharmacokinetics and the parametric images of [N-methyl-11C]α-methylaminoisobutyric acid ([¹¹C]-MeAIB) as a marker of system A transport and of [S-methyl-¹¹C]-L-methionine ([¹¹C]-MET) as a marker of system L.

Methods Six normal healthy subjects received intravenous injection of both [¹¹C]-MeAIB and [¹¹C]-MET, respectively in other day, and dynamic and static PET images were obtained. Plasma and pancreas time-activity curve were analyzed graphically using pharmacokinetic modeling with 1 tissue-compartment modeling, followed by the voxel-based parametric image analysis.

Results In both PET images, peak plasma accumulation were observed in 2 min after injection and decreased tri-exponentially, while pancreas showed constant increased uptake because of system A and L amino acid transports. In pharmacokinetic modeling from the time-activity curves, parameters of K1, K2 and Vt were 0.21±0.12, 0.10±0.06, 1.99±0.19 for [¹¹C]-MeAIB and 0.44±0.05, 0.04±0.03, 10.46±4.32 for [¹¹C]-MET, respectively (P<0.01).

Conclusions System A and L amino acid transport image analysis were obtained with [¹¹C]-MeAIB and [¹¹C]-MET PET in human pancreas. These PET imaging would contribute to assess the activity of amino acid transports in various diseases such as neoplasm.