Test-retest reproducibility of [11C]-Ldeprenyl-D2 binding to MAO-B in the human brain

Background: [C-11]-L-deprenyl-D-2 is a positron emission tomography (PET) radioligand for measurement of the monoamine oxidase B (MAO-B) activity in vivo brain. The estimation of the test-retest reproducibility is important for accurate interpretation of PET studies. Results: We performed two [C-11]-L-deprenyl-D-2 scans for six healthy subjects and evaluated the test-retest variability of this radioligand. MAO-B binding was quantified by two tissue compartment model (2TCM) with three rate constants (K-1, k(2), k(3)) using metabolite-corrected plasma radioactivity. The lambda k(3) defined as (K-1/k(2)) x k(3) was also calculated. The correlation between MAO-B binding and age, and the effect of partial volume effect correction (PVEc) for the reproducibility were also estimated. % difference of k(3) was 2.6% (medial frontal cortex) to 10.3% (hippocampus), and that of lambda k(3) was 5.0% (thalamus) to 9.2% (cerebellum). Mean % difference of all regions were 5.3 and 7.0% in k(3) and lambda k(3), respectively. All regions showed below 10% variabilities except the hippocampus in k(3) (10.3%). Intraclass correlation coefficient (ICC) of k(3) was 0.78 (hippocampus) to 0.98 (medial frontal cortex), and that of lambda k(3) was 0.78 (hippocampus) to 0.95 (thalamus). Mean ICC were 0.94 and 0.89 in k(3) and lambda k(3), respectively. The highest positive correlation with age was observed in the hippocampus, as r = 0.75 in k(3) and 0.76 in lambda k(3). After PVEc, mean % difference were 5.6 and 7.2% in k(3) and lambda k(3), respectively. Mean ICC were 0.92 and 0.90 for k(3) and lambda k(3,) respectively. These values were almost the same as those before PVEc. Conclusions: The present results indicate that k(3) and.k(3) of [C-11]-L-deprenyl-D-2 are reliable parameters for test-retest reproducibility with healthy subjects both before and after PVEc. The studies with patients of larger sample size are required for further clinical applications.